Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
Hi Neil, On 5 October 2016 at 18:44, NeilBrownwrote: > On Wed, Oct 05 2016, Felipe Balbi wrote: > >> Hi Baolin, >> >> Baolin Wang writes: > But you do! > The mA number from the USB configuration is passed to > usb_gadget_vbus_draw. > Your patch passes that to usb_charger_set_cur_limit_by_type() > which calls __usb_charger_set_cur_limit_by_type() which will set the > cur_limit for whichever type uchger->type currently is. > > So when it is not relevant, your code *does* set some current limit. Suppose the charger type is DCP(it is not relevant to the mA number from the USB configuration ), it will not do the USB enumeration, then no USB configuration from host to set current. >>> >>> From the talking, there are some issues (thanks for Neil's comments) >>> need to be fixed as below: >>> 1. Need to add the method getting charger type from extcon subsystem. >>> 2. Need to remove the method getting charger type from power supply. >>> 3. There are still some different views about reporting the maximum >>> current or minimum current to power driver. >>> >>> Now the current v16 patchset can work well on my Spreadtrum platform >>> and Jun's NXP platform, if you like to apply this patchset then I can > > I'm really curious how much testing this has had. Have you actually > plugged in different cable types (SDP DCP DCP ACA) and has each one been > detected correctly? Because I cannot see how that could happen with the > code you have posted. I transplanted the USB charger framework to our Spreadtrum platform with implementing the 'get_charger_type' callback to get the charger type in power driver. Cause we get the charger type from accessing the PMIC registers not from USB PHY. > >>> send out new patches to fix above issues. If you don't like that, I >>> can send out new version patchset to fix above issues. Could you give >>> me some suggestions what should I do next step? Thanks. >> >> Merge window just opened, nothing will happen for about 2 weeks. How >> about you send a new version after merge window closes and we go from >> there? Fixing 1 and 2 is needed. 3 we need to consider more >> carefully. Perhaps report both minimum and maximum somehow? >> >> Neil, comments? > > This probably seems a bit harsh, but I really think the current patchset > should be discarded and the the project started again with a clear > vision of what is required. What we currently have is too confused. Probably not. Now the USB charger framework tried to integrate all different charger plugged/unplugged events, and all different charger type getting methods, then noticed the plugged/unplugged events and charger current to power driver, which I think that is what USB charger should really do. Moreover, this patchset is reviewed and helped by many people (thanks Felipe, Greg, Mark, Peter and Jun), I really hope I can make it better to upstream. > > To respond to the points: >>> 1. Need to add the method getting charger type from extcon subsystem. > > Yes. This should be the only way to get the charger type. Not really. Like I said, some platform's charger detection is done by hardware not USB PHY, thus we can get the charger type from PMIC hardware registers. > >>> 2. Need to remove the method getting charger type from power supply. > > Also need to remove the ->get_charger_type() method as there is no > credible use-case for this. No. User can implement the get_charger_type() method to access the PMIC registers to get the charger type, which is one very common method. > >>> 3. There are still some different views about reporting the maximum >>> current or minimum current to power driver. > > I think those were resolved. There was some confusion over whether a > particular power manager wanted to be told the maximum or the minimum, > but I think both have a clear use case in different hardware. So, seems I should report both minimum and maximum. > > Also: We don't want another notifier_chain. The usb_notifier combined > with the extcon notifier are sufficient. Possibly it would be sensible > to replace the usb notifier with a new new notifier chain, but don't add > something without first cleaning up what is there. USB charger is one virtual device not one actual hardware device, we should not mess it together with usb_notifier or extcon notifier. > > Also: resolve the question of whether it could ever make sense to have > more than one "usb_charger" in a system. If it doesn't, make it an > obvious singleton. If it does, make it clear how the correct > usb_charger is chosen. Usually only one USB charger in one system, I have not seen more than one charger in a system. > > Also: think very carefully before exposing any details through sysfs. > Some of the details are already visible, either in sys/class/extcon > or sys/class/power_supply. Don't duplicate without good reason. I think now the current/state/type
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
On Wed, Oct 05 2016, Felipe Balbi wrote: > Hi Baolin, > > Baolin Wangwrites: But you do! The mA number from the USB configuration is passed to usb_gadget_vbus_draw. Your patch passes that to usb_charger_set_cur_limit_by_type() which calls __usb_charger_set_cur_limit_by_type() which will set the cur_limit for whichever type uchger->type currently is. So when it is not relevant, your code *does* set some current limit. >>> >>> Suppose the charger type is DCP(it is not relevant to the mA number >>> from the USB configuration ), it will not do the USB enumeration, then >>> no USB configuration from host to set current. >> >> From the talking, there are some issues (thanks for Neil's comments) >> need to be fixed as below: >> 1. Need to add the method getting charger type from extcon subsystem. >> 2. Need to remove the method getting charger type from power supply. >> 3. There are still some different views about reporting the maximum >> current or minimum current to power driver. >> >> Now the current v16 patchset can work well on my Spreadtrum platform >> and Jun's NXP platform, if you like to apply this patchset then I can I'm really curious how much testing this has had. Have you actually plugged in different cable types (SDP DCP DCP ACA) and has each one been detected correctly? Because I cannot see how that could happen with the code you have posted. >> send out new patches to fix above issues. If you don't like that, I >> can send out new version patchset to fix above issues. Could you give >> me some suggestions what should I do next step? Thanks. > > Merge window just opened, nothing will happen for about 2 weeks. How > about you send a new version after merge window closes and we go from > there? Fixing 1 and 2 is needed. 3 we need to consider more > carefully. Perhaps report both minimum and maximum somehow? > > Neil, comments? This probably seems a bit harsh, but I really think the current patchset should be discarded and the the project started again with a clear vision of what is required. What we currently have is too confused. To respond to the points: >> 1. Need to add the method getting charger type from extcon subsystem. Yes. This should be the only way to get the charger type. >> 2. Need to remove the method getting charger type from power supply. Also need to remove the ->get_charger_type() method as there is no credible use-case for this. >> 3. There are still some different views about reporting the maximum >> current or minimum current to power driver. I think those were resolved. There was some confusion over whether a particular power manager wanted to be told the maximum or the minimum, but I think both have a clear use case in different hardware. Also: We don't want another notifier_chain. The usb_notifier combined with the extcon notifier are sufficient. Possibly it would be sensible to replace the usb notifier with a new new notifier chain, but don't add something without first cleaning up what is there. Also: resolve the question of whether it could ever make sense to have more than one "usb_charger" in a system. If it doesn't, make it an obvious singleton. If it does, make it clear how the correct usb_charger is chosen. Also: think very carefully before exposing any details through sysfs. Some of the details are already visible, either in sys/class/extcon or sys/class/power_supply. Don't duplicate without good reason. NeilBrown > > -- > balbi signature.asc Description: PGP signature
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
Hi Felipe, On 5 October 2016 at 15:47, Felipe Balbiwrote: > > Hi Baolin, > > Baolin Wang writes: But you do! The mA number from the USB configuration is passed to usb_gadget_vbus_draw. Your patch passes that to usb_charger_set_cur_limit_by_type() which calls __usb_charger_set_cur_limit_by_type() which will set the cur_limit for whichever type uchger->type currently is. So when it is not relevant, your code *does* set some current limit. >>> >>> Suppose the charger type is DCP(it is not relevant to the mA number >>> from the USB configuration ), it will not do the USB enumeration, then >>> no USB configuration from host to set current. >> >> From the talking, there are some issues (thanks for Neil's comments) >> need to be fixed as below: >> 1. Need to add the method getting charger type from extcon subsystem. >> 2. Need to remove the method getting charger type from power supply. >> 3. There are still some different views about reporting the maximum >> current or minimum current to power driver. >> >> Now the current v16 patchset can work well on my Spreadtrum platform >> and Jun's NXP platform, if you like to apply this patchset then I can >> send out new patches to fix above issues. If you don't like that, I >> can send out new version patchset to fix above issues. Could you give >> me some suggestions what should I do next step? Thanks. > > Merge window just opened, nothing will happen for about 2 weeks. How > about you send a new version after merge window closes and we go from > there? Fixing 1 and 2 is needed. 3 we need to consider more Sure. I will send out the new version with fixing these issues. Thanks. > carefully. Perhaps report both minimum and maximum somehow? > > Neil, comments? > > -- > balbi -- Baolin.wang Best Regards -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
Hi Baolin, Baolin Wangwrites: >>> But you do! >>> The mA number from the USB configuration is passed to usb_gadget_vbus_draw. >>> Your patch passes that to usb_charger_set_cur_limit_by_type() >>> which calls __usb_charger_set_cur_limit_by_type() which will set the >>> cur_limit for whichever type uchger->type currently is. >>> >>> So when it is not relevant, your code *does* set some current limit. >> >> Suppose the charger type is DCP(it is not relevant to the mA number >> from the USB configuration ), it will not do the USB enumeration, then >> no USB configuration from host to set current. > > From the talking, there are some issues (thanks for Neil's comments) > need to be fixed as below: > 1. Need to add the method getting charger type from extcon subsystem. > 2. Need to remove the method getting charger type from power supply. > 3. There are still some different views about reporting the maximum > current or minimum current to power driver. > > Now the current v16 patchset can work well on my Spreadtrum platform > and Jun's NXP platform, if you like to apply this patchset then I can > send out new patches to fix above issues. If you don't like that, I > can send out new version patchset to fix above issues. Could you give > me some suggestions what should I do next step? Thanks. Merge window just opened, nothing will happen for about 2 weeks. How about you send a new version after merge window closes and we go from there? Fixing 1 and 2 is needed. 3 we need to consider more carefully. Perhaps report both minimum and maximum somehow? Neil, comments? -- balbi signature.asc Description: PGP signature
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
Hi Felipe, >> But you do! >> The mA number from the USB configuration is passed to usb_gadget_vbus_draw. >> Your patch passes that to usb_charger_set_cur_limit_by_type() >> which calls __usb_charger_set_cur_limit_by_type() which will set the >> cur_limit for whichever type uchger->type currently is. >> >> So when it is not relevant, your code *does* set some current limit. > > Suppose the charger type is DCP(it is not relevant to the mA number > from the USB configuration ), it will not do the USB enumeration, then > no USB configuration from host to set current. >From the talking, there are some issues (thanks for Neil's comments) need to be fixed as below: 1. Need to add the method getting charger type from extcon subsystem. 2. Need to remove the method getting charger type from power supply. 3. There are still some different views about reporting the maximum current or minimum current to power driver. Now the current v16 patchset can work well on my Spreadtrum platform and Jun's NXP platform, if you like to apply this patchset then I can send out new patches to fix above issues. If you don't like that, I can send out new version patchset to fix above issues. Could you give me some suggestions what should I do next step? Thanks. > > -- > Baolin.wang > Best Regards -- Baolin.wang Best Regards -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
Hi Neil, Sorry for late reply due yo my holiday. On 10 September 2016 at 05:19, NeilBrownwrote: > On Fri, Sep 09 2016, Baolin Wang wrote: > >>> >>> In practice, the USB PHY and the Power manager will often be in the same >>> IC (the PMIC) so the driver for one could look at the registers for the >>> other. >>> But there is no guarantee that the hardware works like that. It is >>> best to create a generally design. >> >> Yes, we hope to create one generally design, so we need to consider >> this situation: the power supply getting the charger type by accessing >> PMIC registers. The registers which save the charger type are not >> always belong to the USB PHY, may be just some registers on PMIC. > > If the power_supply can directly detect the type of charger, then it > doesn't need any usb-charger-infrastructure to tell it. It can handle > current selection entirely internally. > Surely the only interesting case for a framework to address is the one > where the power_supply cannot directly detect the charger type. But power supply also need one plugged or unplugged event to set current from USB charger framework. Another hand, considering one generic framework, since power supply support API (e.g.: power_supply_get_property()) to get charger type for others, we should integrate power supply into USB charger framework. > >> >> Now in mainline kernel, there are 3 methods can get the charger type >> which need to integrate with USB charger framework: >> 1. power supply >> 2. extcon (need to add as you suggested) >> 3. others (by 'get_charger_type' callback of USB charger) > > There is no "get_charger_type" now in the mainline kernel. We want to create one generic framework, thus we should consider some users want to implement the function to get charger type by accessing PMIC registers or else. > Suppose the USB configuration requests 100mA, then we should set the USB charger current is 100mA by __usb_charger_set_cur_limit_by_type() funtion, then notify this to power driver. >>> >>> ahh I had missed something there. It's a while since I looked >>> closely at these patches. >>> >>> Only this usage of usb_charger_set_cur_limit_by_type() is really >>> nonsensical. >>> >>> If the cable is detected as being DCP or CDP or ACA (or ACA/DOCK) then >>> the number negotiated with the USB configuration is not relevant and >>> should be ignored. There is a guaranteed minimum which is at least the >>> maximum that *can* be negotiated. >> >> Yes. If it is not relevant, we will no't set the current from USB >> configuration. Just when your charger type is SDP and the USB >> enumeration is done, we can get the USB configuration from host to set >> current. > > But you do! > The mA number from the USB configuration is passed to usb_gadget_vbus_draw. > Your patch passes that to usb_charger_set_cur_limit_by_type() > which calls __usb_charger_set_cur_limit_by_type() which will set the > cur_limit for whichever type uchger->type currently is. > > So when it is not relevant, your code *does* set some current limit. Suppose the charger type is DCP(it is not relevant to the mA number from the USB configuration ), it will not do the USB enumeration, then no USB configuration from host to set current. -- Baolin.wang Best Regards -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
Hi! > > That's not actually 100% clear to me - for what the wm831x is doing it > > probably *does* want the higher limit. This is a system inflow limit > > (as it should be for this), at least the charger will adapt to voltage > > variations though other users in the system are much less likely to do > > so. > > Interesting ... I hadn't considered that possibility. > > As long as the current remains below the maximum, the charger will > reduce the voltage towards 2V as load increases. Somewhere before it > gets there, the system will not be able to make use of the power as the > voltage will be too low to be usable. So that will naturally limit the > current being drawn. > > Not having very much electrical engineering background, I cannot say for > sure what will happen, but it seems likely that once the voltage drops > much below 4.75V, the charger won't be operating at peak efficiency, > which would be a waste. > I can easily imagine that the hardware would switch off at some voltage > level, rather than just making do with what is there. > So I'm skeptical of this approach, but I'm open to being corrected by > someone more knowledgeable than I. Devices I seen charge down to ~4.2V. This is useful thing to play with: dx.com: 406496 1" USB Current & Voltage Detector Tester Meter w/ Red LED Display - Blue Best regards, Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
On Wed, Sep 14, 2016 at 07:50:00PM +0200, NeilBrown wrote: > On Wed, Sep 14 2016, Mark Brown wrote: > Ah my mistake, sorry. > When earlier you said: > > It's a > > current limiter intended to sit in line with the USB power lines to > I assumed that all it did was limit the current to number given. > If it also limits the current to ensure that voltage doesn't drop > unduly, then I agree with your assertion that it just needs to be told > the upper limit. Oh, I see the gap here - the USB specific bit is only a current limiter but it works in concert with other bits of the system that try to stop the voltage from whatever supply is in use from dropping and can't be used independently of them. That's why I wasn't clear in what I said! > I hope you'll agree that other drivers might need to know the lower > limit, so reporting both to all drivers is sensible. Yes, absolutely. signature.asc Description: PGP signature
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
On Wed, Sep 14 2016, Mark Brown wrote: > TI do a lot of the more software managed chargers (which I suspect are > the main thing Felipe will have looked at) if that's what you're > referring to here? The device is implementing pretty much the algorithm > you're describing in that e-mail so I'm a bit confused as to what you're > saying here. Ah my mistake, sorry. When earlier you said: > It's a > current limiter intended to sit in line with the USB power lines to > ensure the system doesn't go over the maximum current draw (and also > integrates with the power source selection logic the chip has to pick > the best available power source for the system). I assumed that all it did was limit the current to number given. If it also limits the current to ensure that voltage doesn't drop unduly, then I agree with your assertion that it just needs to be told the upper limit. I hope you'll agree that other drivers might need to know the lower limit, so reporting both to all drivers is sensible. Thanks, NeilBrown signature.asc Description: PGP signature
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
On Wed, Sep 14, 2016 at 04:11:58PM +0200, NeilBrown wrote: > On Wed, Sep 14 2016, Mark Brown wrote: > > Yes, the idea is that the charger will back off charging and stop > > entirely if the rest of the system is consuming too much power to allow > > it to continue effectively. The same thing happens with wall power, if > > a wall supply isn't able to power the charger (eg, because the rest of > > the system is running flat out) it'll have to cope with that. > Maybe you are correct. I don't find your argument convincing, but maybe > that is because I don't want to... There's a *huge* variation in how chargers are designed, some are designed to be dumb and won't function without software while the wm831x is more at the opposite end of the spectrum and will quite happily run all the charging and power source selection logic with no software intervention at all - the parameters it uses can be changed at runtime but that's about it. Software implementations are obviously more flexible but hardware implementations can be more responsive to changes in system state like drooping supplies and aren't vulnerable to things like software lockups. > 1/ I had a report once from someone whose device stopped charging > because it was pulling more current than the charger could supply. > The voltage dropped below the 3.5V (I think) that the battery > charging hardware needed, so it switched off. It wouldn't switch > back on again until explicitly told too. It would then overload the > charger again and switch off. That's just one charger's algorithm though, other options are available. > Which seems to say the maximum is just for safety, implying that the > minimum is the important value. This is what I was saying about a sensible reading being for the supply and consumer side to directly target the maximum and minimum limits respectively (though for the battery charger spec it's a bit different as the range is so wide). > 3/ Felipe Balbiappears to agree with my >perspective. > http://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1224904.html >does argument-by-authority work? TI do a lot of the more software managed chargers (which I suspect are the main thing Felipe will have looked at) if that's what you're referring to here? The device is implementing pretty much the algorithm you're describing in that e-mail so I'm a bit confused as to what you're saying here. signature.asc Description: PGP signature
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
On Wed, Sep 14 2016, Mark Brown wrote: > [ Unknown signature status ] > On Tue, Sep 13, 2016 at 10:00:28AM +0200, NeilBrown wrote: >> On Mon, Sep 12 2016, Mark Brown wrote: > >> > That's not actually 100% clear to me - for what the wm831x is doing it >> > probably *does* want the higher limit. This is a system inflow limit >> > (as it should be for this), at least the charger will adapt to voltage >> > variations though other users in the system are much less likely to do >> > so. > >> Not having very much electrical engineering background, I cannot say for >> sure what will happen, but it seems likely that once the voltage drops >> much below 4.75V, the charger won't be operating at peak efficiency, >> which would be a waste. >> I can easily imagine that the hardware would switch off at some voltage >> level, rather than just making do with what is there. >> So I'm skeptical of this approach, but I'm open to being corrected by >> someone more knowledgeable than I. > > Yes, the idea is that the charger will back off charging and stop > entirely if the rest of the system is consuming too much power to allow > it to continue effectively. The same thing happens with wall power, if > a wall supply isn't able to power the charger (eg, because the rest of > the system is running flat out) it'll have to cope with that. Maybe you are correct. I don't find your argument convincing, but maybe that is because I don't want to... Some facts though: 1/ I had a report once from someone whose device stopped charging because it was pulling more current than the charger could supply. The voltage dropped below the 3.5V (I think) that the battery charging hardware needed, so it switched off. It wouldn't switch back on again until explicitly told too. It would then overload the charger again and switch off. Changing the code to put a lower limit on the current allowed the battery to be charged. So empirical evidence suggests that the lower number should be used. 2/ I hoped that Battery Charging Specification Revision 1.2 December 7, 2010 would say something definite, but I cannot find it. However, "note 1" to "Table 5-2 Currents" says: 1) The maximum current is for safety reasons, as per USB 2.0 section 7.2.1.2.1. Which seems to say the maximum is just for safety, implying that the minimum is the important value. 3/ Felipe Balbiappears to agree with my perspective. http://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1224904.html does argument-by-authority work? > >> Looking at it from a different perspective, according to the patch set, >> the limits that wm831x is able to impose are: > >> + 0, >> + 2, >> + 100, >> + 500, >> + 900, >> + 1500, >> + 1800, >> + 550, > >> These are, from the battery charger spec, minimums rather than maximums. >> e.g. a CDP provides at least 1500, and as much as 5000. So it seems >> that the wm831x was designed to be told the minimum guaranteed available. >> But that is circumstantial evidence and might be misleading. > > AIUI this is conservatisim in the system design - another way of reading > a spec with a range like this is that the consumer should aim for the > lower limit, the provider should aim for the upper limit and that way if > either of them has issues with tolerances things will still work out. > It predates wide availability of CDP so I wouldn't be surprised if that > bit were just an oversight. Like I say this bit of hardware is totally > separate to the battery charger. Your last sentence is interesting I would reply "of course". All the code we are talking about is only tangentially related to battery charging. It is about how much current can safely be pulled from a USB port. What that current is used for is a completely separate question. NeilBrown signature.asc Description: PGP signature
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
On Tue, Sep 13, 2016 at 10:00:28AM +0200, NeilBrown wrote: > On Mon, Sep 12 2016, Mark Brown wrote: > > That's not actually 100% clear to me - for what the wm831x is doing it > > probably *does* want the higher limit. This is a system inflow limit > > (as it should be for this), at least the charger will adapt to voltage > > variations though other users in the system are much less likely to do > > so. > Not having very much electrical engineering background, I cannot say for > sure what will happen, but it seems likely that once the voltage drops > much below 4.75V, the charger won't be operating at peak efficiency, > which would be a waste. > I can easily imagine that the hardware would switch off at some voltage > level, rather than just making do with what is there. > So I'm skeptical of this approach, but I'm open to being corrected by > someone more knowledgeable than I. Yes, the idea is that the charger will back off charging and stop entirely if the rest of the system is consuming too much power to allow it to continue effectively. The same thing happens with wall power, if a wall supply isn't able to power the charger (eg, because the rest of the system is running flat out) it'll have to cope with that. > Looking at it from a different perspective, according to the patch set, > the limits that wm831x is able to impose are: > +0, > +2, > +100, > +500, > +900, > +1500, > +1800, > +550, > These are, from the battery charger spec, minimums rather than maximums. > e.g. a CDP provides at least 1500, and as much as 5000. So it seems > that the wm831x was designed to be told the minimum guaranteed available. > But that is circumstantial evidence and might be misleading. AIUI this is conservatisim in the system design - another way of reading a spec with a range like this is that the consumer should aim for the lower limit, the provider should aim for the upper limit and that way if either of them has issues with tolerances things will still work out. It predates wide availability of CDP so I wouldn't be surprised if that bit were just an oversight. Like I say this bit of hardware is totally separate to the battery charger. signature.asc Description: PGP signature
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
On Mon, Sep 12 2016, Mark Brown wrote: > [ Unknown signature status ] > On Mon, Sep 12, 2016 at 03:27:18PM +0200, NeilBrown wrote: >> On Mon, Sep 12 2016, Mark Brown wrote: > >> > It's no worse than any other board file situation - if someone has that >> > problem they get to fix it. > >> My point is that the present design does not appear to scale beyond a >> single USB power supply (as if there were two, they would be named in >> discovery order, which is not reliably stable). > > For the practical purposes of people making systems (as opposed to > upstream where this is likely to get most use) it pretty much is. > Though quite how many systems have multiple chargers is itself also a > question. > >> Your point is, I think, that when someone actually cares about that lack >> of scaling, they can fix it. > > Yes. > >> I am perfectly happy with that approach. However if the code doesn't >> scale beyond one charger, it shouldn't pretend that it does. >> i.e. >> Don't have "usb_charger_find_by_name()", just a global "usb_charger" >> (or similar). >> The first charger to register gets to be the "usb_charger". The >> second one gets an error. >> I could be quite happy with that sort of interface. > > Well, a fairly standard way of extending would be to allow the explicit > assignment of names to chargers so this'd avoid such churn. Sure, that might work. I'm just against a design that obviously cannot work. > >> > The whole point from the point of view of the wm831x driver is that it >> > just wants something to tell it how much current it's allowed to draw, I >> > appreciate that doesn't change your analysis of the bit in the middle >> > but the consumer driver bit seems fine here. > >> Yes, the wm831x driver probably does the right thing. >> Other drivers might want to know not only the minimum they are allowed >> to draw, but also the maximum they should try even if they are carefully >> monitoring the voltage. >> So wm831x is doing the right thing with the wrong interface. Maybe you >> can describe that as "fine". > > That's not actually 100% clear to me - for what the wm831x is doing it > probably *does* want the higher limit. This is a system inflow limit > (as it should be for this), at least the charger will adapt to voltage > variations though other users in the system are much less likely to do > so. Interesting ... I hadn't considered that possibility. As long as the current remains below the maximum, the charger will reduce the voltage towards 2V as load increases. Somewhere before it gets there, the system will not be able to make use of the power as the voltage will be too low to be usable. So that will naturally limit the current being drawn. Not having very much electrical engineering background, I cannot say for sure what will happen, but it seems likely that once the voltage drops much below 4.75V, the charger won't be operating at peak efficiency, which would be a waste. I can easily imagine that the hardware would switch off at some voltage level, rather than just making do with what is there. So I'm skeptical of this approach, but I'm open to being corrected by someone more knowledgeable than I. Looking at it from a different perspective, according to the patch set, the limits that wm831x is able to impose are: + 0, + 2, + 100, + 500, + 900, + 1500, + 1800, + 550, These are, from the battery charger spec, minimums rather than maximums. e.g. a CDP provides at least 1500, and as much as 5000. So it seems that the wm831x was designed to be told the minimum guaranteed available. But that is circumstantial evidence and might be misleading. NeilBrown signature.asc Description: PGP signature
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
On Mon, Sep 12, 2016 at 03:27:18PM +0200, NeilBrown wrote: > On Mon, Sep 12 2016, Mark Brown wrote: > > It's no worse than any other board file situation - if someone has that > > problem they get to fix it. > My point is that the present design does not appear to scale beyond a > single USB power supply (as if there were two, they would be named in > discovery order, which is not reliably stable). For the practical purposes of people making systems (as opposed to upstream where this is likely to get most use) it pretty much is. Though quite how many systems have multiple chargers is itself also a question. > Your point is, I think, that when someone actually cares about that lack > of scaling, they can fix it. Yes. > I am perfectly happy with that approach. However if the code doesn't > scale beyond one charger, it shouldn't pretend that it does. > i.e. > Don't have "usb_charger_find_by_name()", just a global "usb_charger" > (or similar). > The first charger to register gets to be the "usb_charger". The > second one gets an error. > I could be quite happy with that sort of interface. Well, a fairly standard way of extending would be to allow the explicit assignment of names to chargers so this'd avoid such churn. > > The whole point from the point of view of the wm831x driver is that it > > just wants something to tell it how much current it's allowed to draw, I > > appreciate that doesn't change your analysis of the bit in the middle > > but the consumer driver bit seems fine here. > Yes, the wm831x driver probably does the right thing. > Other drivers might want to know not only the minimum they are allowed > to draw, but also the maximum they should try even if they are carefully > monitoring the voltage. > So wm831x is doing the right thing with the wrong interface. Maybe you > can describe that as "fine". That's not actually 100% clear to me - for what the wm831x is doing it probably *does* want the higher limit. This is a system inflow limit (as it should be for this), at least the charger will adapt to voltage variations though other users in the system are much less likely to do so. signature.asc Description: PGP signature
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
On Mon, Sep 12 2016, Mark Brown wrote: > [ Unknown signature status ] > On Sat, Sep 10, 2016 at 07:57:26AM +1000, NeilBrown wrote: >> On Fri, Sep 09 2016, Mark Brown wrote: > >> > The wm831x driver in the patch series is an example of such hardware - >> > it is purely a power manager, it has no USB PHY hardware at all. It's a > >> The "probe" routine calls > >> + usb_charger_find_by_name(wm831x_pdata->usb_gadget); > >> Presumably wm831x_pdata is initialised by a board file? > > Yes. > >> I strongly suspect it is initialized to "usb-charger.0" because the >> names given to usb chargers are "usb-charger.%d" in discovery order. >> I don't see this being at all useful if there is ever more than one >> usb-charger. >> Do you? > > It's no worse than any other board file situation - if someone has that > problem they get to fix it. My point is that the present design does not appear to scale beyond a single USB power supply (as if there were two, they would be named in discovery order, which is not reliably stable). Your point is, I think, that when someone actually cares about that lack of scaling, they can fix it. I am perfectly happy with that approach. However if the code doesn't scale beyond one charger, it shouldn't pretend that it does. i.e. Don't have "usb_charger_find_by_name()", just a global "usb_charger" (or similar). The first charger to register gets to be the "usb_charger". The second one gets an error. I could be quite happy with that sort of interface. > >> So how can this wm831x driver actually find out what sort of charger is >> connected and so set the power limit? I just don't see this working *at* >> *all*. > > The whole point from the point of view of the wm831x driver is that it > just wants something to tell it how much current it's allowed to draw, I > appreciate that doesn't change your analysis of the bit in the middle > but the consumer driver bit seems fine here. Yes, the wm831x driver probably does the right thing. Other drivers might want to know not only the minimum they are allowed to draw, but also the maximum they should try even if they are carefully monitoring the voltage. So wm831x is doing the right thing with the wrong interface. Maybe you can describe that as "fine". NeilBrown signature.asc Description: PGP signature
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
On Sat, Sep 10, 2016 at 07:57:26AM +1000, NeilBrown wrote: > On Fri, Sep 09 2016, Mark Brown wrote: > > The wm831x driver in the patch series is an example of such hardware - > > it is purely a power manager, it has no USB PHY hardware at all. It's a > The "probe" routine calls > +usb_charger_find_by_name(wm831x_pdata->usb_gadget); > Presumably wm831x_pdata is initialised by a board file? Yes. > I strongly suspect it is initialized to "usb-charger.0" because the > names given to usb chargers are "usb-charger.%d" in discovery order. > I don't see this being at all useful if there is ever more than one > usb-charger. > Do you? It's no worse than any other board file situation - if someone has that problem they get to fix it. > So how can this wm831x driver actually find out what sort of charger is > connected and so set the power limit? I just don't see this working *at* > *all*. The whole point from the point of view of the wm831x driver is that it just wants something to tell it how much current it's allowed to draw, I appreciate that doesn't change your analysis of the bit in the middle but the consumer driver bit seems fine here. signature.asc Description: PGP signature
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
On Fri, Sep 09 2016, Mark Brown wrote: > [ Unknown signature status ] > On Fri, Sep 09, 2016 at 09:13:31AM +1000, NeilBrown wrote: > >> Conceptually, the PHY is separate from the power manager and a solution >> which recognises that will be more universal. > > The wm831x driver in the patch series is an example of such hardware - > it is purely a power manager, it has no USB PHY hardware at all. It's a > current limiter intended to sit in line with the USB power lines to > ensure the system doesn't go over the maximum current draw (and also > integrates with the power source selection logic the chip has to pick > the best available power source for the system). It might be instructive to look at exactly what happens with this device. The "probe" routine calls + usb_charger_find_by_name(wm831x_pdata->usb_gadget); Presumably wm831x_pdata is initialised by a board file? I strongly suspect it is initialized to "usb-charger.0" because the names given to usb chargers are "usb-charger.%d" in discovery order. I don't see this being at all useful if there is ever more than one usb-charger. Do you? The probe function then registers for charger notifications. When they arrive, wm831x_usb_limit_change() will set the highest supported limit which is less than the notified "limit". So presumably that "limit" must be the minimum guaranteed by the charger type. Let's see when the notification is called... ->uchgr_nh is sent a notification from usb_charger_notify_others() with (in the "charger is present" case) the value of __usb_charger_get_cur_limit(uchger) which just pulls values out of the cur_limit structure, based on the type, reported by usb_charger_get_type_by_others(uchger); (The default values in this structure are not the minimums guaranteed by the charger types, they are generally higher. So this could easily result in the charger shutting down). usb_charger_get_type_by_others() has two ways to get the charger type, which it then caches in uchger->type until the charger is removed. If there is a uchger->psy power supply, then the POWER_SUPPLY_PROP_CHARGE_TYPE property is used... Oh, that is weird. The valid values for that property are: enum { POWER_SUPPLY_CHARGE_TYPE_UNKNOWN = 0, POWER_SUPPLY_CHARGE_TYPE_NONE, POWER_SUPPLY_CHARGE_TYPE_TRICKLE, POWER_SUPPLY_CHARGE_TYPE_FAST, }; but the code in usb_charger_get_type_by_others() compares it against: + case POWER_SUPPLY_TYPE_USB: + case POWER_SUPPLY_TYPE_USB_DCP: + case POWER_SUPPLY_TYPE_USB_CDP: + case POWER_SUPPLY_TYPE_USB_ACA: Presumably that it just a bug and it was meant to request the POWER_SUPPLY_PROP_TYPE ?? I wonder how much testing was done on this code? Anyway, assuming it is meant to request the TYPE, where is that set? The new code doesn't set it at all. Only three existing power supplies set any of POWER_SUPPLY_TYPE_USB_* axp288_charger.c gpio-charger.c isp1704_charger.c As I wrote in https://lwn.net/Articles/694062/ axp288_charger.c is broken and cannot possibly work. gpio-charger.c configures the type at boot-time so it cannot sensibly detect a newly plugged in charger (how does that make any sense) and isp1704_charger.c peeks in the usb registers (ULPI) to work out the charger type. None of these set the POWER_SUPPLY_PROP_TYPE in a useful way, so why would usb_charger_get_type_by_others() want to use that property? Maybe it really does want to use POWER_SUPPLY_PROP_CHARGE_TYPE? Quite a few chargers set that. It would be a challenge to map names like "TRICKLE" and "FAST" into mA values for a current limiter though. My hardware knowledge is running out here.. I see wm8350_power.c reports that property, but I don't know how that device fits into the picture. With the patch, that driver would request that property from somewhere else(?) and also report it. That is kind-a strange. The other possible source for the charger type is a call to uchger->get_charger_type() There is no get_charger_type() function anywhere in the patchset. No code ever sets that field in the uchger. So how can this wm831x driver actually find out what sort of charger is connected and so set the power limit? I just don't see this working *at* *all*. NeilBrown signature.asc Description: PGP signature
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
On Fri, Sep 09 2016, Baolin Wang wrote: >> >> In practice, the USB PHY and the Power manager will often be in the same >> IC (the PMIC) so the driver for one could look at the registers for the >> other. >> But there is no guarantee that the hardware works like that. It is >> best to create a generally design. > > Yes, we hope to create one generally design, so we need to consider > this situation: the power supply getting the charger type by accessing > PMIC registers. The registers which save the charger type are not > always belong to the USB PHY, may be just some registers on PMIC. If the power_supply can directly detect the type of charger, then it doesn't need any usb-charger-infrastructure to tell it. It can handle current selection entirely internally. Surely the only interesting case for a framework to address is the one where the power_supply cannot directly detect the charger type. > > Now in mainline kernel, there are 3 methods can get the charger type > which need to integrate with USB charger framework: > 1. power supply > 2. extcon (need to add as you suggested) > 3. others (by 'get_charger_type' callback of USB charger) There is no "get_charger_type" now in the mainline kernel. >>> >>> Suppose the USB configuration requests 100mA, then we should set the >>> USB charger current is 100mA by __usb_charger_set_cur_limit_by_type() >>> funtion, then notify this to power driver. >> >> ahh I had missed something there. It's a while since I looked >> closely at these patches. >> >> Only this usage of usb_charger_set_cur_limit_by_type() is really >> nonsensical. >> >> If the cable is detected as being DCP or CDP or ACA (or ACA/DOCK) then >> the number negotiated with the USB configuration is not relevant and >> should be ignored. There is a guaranteed minimum which is at least the >> maximum that *can* be negotiated. > > Yes. If it is not relevant, we will no't set the current from USB > configuration. Just when your charger type is SDP and the USB > enumeration is done, we can get the USB configuration from host to set > current. But you do! The mA number from the USB configuration is passed to usb_gadget_vbus_draw. Your patch passes that to usb_charger_set_cur_limit_by_type() which calls __usb_charger_set_cur_limit_by_type() which will set the cur_limit for whichever type uchger->type currently is. So when it is not relevant, your code *does* set some current limit. NeilBrown signature.asc Description: PGP signature
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
On Fri, Sep 09, 2016 at 09:13:31AM +1000, NeilBrown wrote: > Conceptually, the PHY is separate from the power manager and a solution > which recognises that will be more universal. The wm831x driver in the patch series is an example of such hardware - it is purely a power manager, it has no USB PHY hardware at all. It's a current limiter intended to sit in line with the USB power lines to ensure the system doesn't go over the maximum current draw (and also integrates with the power source selection logic the chip has to pick the best available power source for the system). signature.asc Description: PGP signature
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
On 9 September 2016 at 07:13, NeilBrownwrote: > On Thu, Sep 08 2016, Baolin Wang wrote: > >> On 8 September 2016 at 15:31, NeilBrown wrote: >>> On Thu, Sep 08 2016, Baolin Wang wrote: Now the usb charger will not get charger type from 'extcon' subsystem, we get the charger type from 'power_supply' and calllback 'get_charger_type' for users. >>> >>> I understand this. I think it is wrong because, in general, the >>> power_supply doesn't know what the charger_type is (it might know it is >>> USB, but most don't know which sort of USB). The PHY knows that, not >>> the power_supply. >> >> I don't think so. Now many platforms will detect the charger type by >> PMIC hardware, and we can get the charger type by PMIC hardware >> register. Then power supply driver can access the PMIC register to get >> the charger type. Here USB charger just considers if the accessing the >> PMIC register to get charger type is implemented in power supply, it >> is optional depending on what your platform designed. >> > > In practice, the USB PHY and the Power manager will often be in the same > IC (the PMIC) so the driver for one could look at the registers for the > other. > But there is no guarantee that the hardware works like that. It is > best to create a generally design. Yes, we hope to create one generally design, so we need to consider this situation: the power supply getting the charger type by accessing PMIC registers. The registers which save the charger type are not always belong to the USB PHY, may be just some registers on PMIC. Now in mainline kernel, there are 3 methods can get the charger type which need to integrate with USB charger framework: 1. power supply 2. extcon (need to add as you suggested) 3. others (by 'get_charger_type' callback of USB charger) > Conceptually, the PHY is separate from the power manager and a solution > which recognises that will be more universal. > > If the power manager can always just look at that phy registers to know > what sort of charger is connected, why does you framework need to work > with charger types at all? > Yes, but you must think about some special cases on some platforms. Users may need to change the current in some situations, thus we should export one API for users to change the current. (I think you misunderstand the current limit here, that is the current for power driver to draw). >>> >>> Can you be specific about these "special cases" please? >>> I cannot think of any. >> >> Suppose the USB configuration requests 100mA, then we should set the >> USB charger current is 100mA by __usb_charger_set_cur_limit_by_type() >> funtion, then notify this to power driver. > > ahh I had missed something there. It's a while since I looked > closely at these patches. > > Only this usage of usb_charger_set_cur_limit_by_type() is really > nonsensical. > > If the cable is detected as being DCP or CDP or ACA (or ACA/DOCK) then > the number negotiated with the USB configuration is not relevant and > should be ignored. There is a guaranteed minimum which is at least the > maximum that *can* be negotiated. Yes. If it is not relevant, we will no't set the current from USB configuration. Just when your charger type is SDP and the USB enumeration is done, we can get the USB configuration from host to set current. > > It is only when the cable appears to be a SDP (standard downstream > port) that the usb-config negotiation is relevant. That is because the > minimum guaranteed for SDP is only 100mA. > > NeilBrown -- Baolin.wang Best Regards -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
On Thu, Sep 08 2016, Baolin Wang wrote: > On 8 September 2016 at 15:31, NeilBrownwrote: >> On Thu, Sep 08 2016, Baolin Wang wrote: >>> >>> Now the usb charger will not get charger type from 'extcon' subsystem, >>> we get the charger type from 'power_supply' and calllback >>> 'get_charger_type' for users. >> >> I understand this. I think it is wrong because, in general, the >> power_supply doesn't know what the charger_type is (it might know it is >> USB, but most don't know which sort of USB). The PHY knows that, not >> the power_supply. > > I don't think so. Now many platforms will detect the charger type by > PMIC hardware, and we can get the charger type by PMIC hardware > register. Then power supply driver can access the PMIC register to get > the charger type. Here USB charger just considers if the accessing the > PMIC register to get charger type is implemented in power supply, it > is optional depending on what your platform designed. > In practice, the USB PHY and the Power manager will often be in the same IC (the PMIC) so the driver for one could look at the registers for the other. But there is no guarantee that the hardware works like that. It is best to create a generally design. Conceptually, the PHY is separate from the power manager and a solution which recognises that will be more universal. If the power manager can always just look at that phy registers to know what sort of charger is connected, why does you framework need to work with charger types at all? >>> >>> Yes, but you must think about some special cases on some platforms. >>> Users may need to change the current in some situations, thus we >>> should export one API for users to change the current. (I think you >>> misunderstand the current limit here, that is the current for power >>> driver to draw). >> >> Can you be specific about these "special cases" please? >> I cannot think of any. > > Suppose the USB configuration requests 100mA, then we should set the > USB charger current is 100mA by __usb_charger_set_cur_limit_by_type() > funtion, then notify this to power driver. ahh I had missed something there. It's a while since I looked closely at these patches. Only this usage of usb_charger_set_cur_limit_by_type() is really nonsensical. If the cable is detected as being DCP or CDP or ACA (or ACA/DOCK) then the number negotiated with the USB configuration is not relevant and should be ignored. There is a guaranteed minimum which is at least the maximum that *can* be negotiated. It is only when the cable appears to be a SDP (standard downstream port) that the usb-config negotiation is relevant. That is because the minimum guaranteed for SDP is only 100mA. NeilBrown signature.asc Description: PGP signature
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
On 8 September 2016 at 15:31, NeilBrownwrote: > On Thu, Sep 08 2016, Baolin Wang wrote: > >> Hi Neil, >> >> On 6 September 2016 at 13:40, NeilBrown wrote: >>> On Mon, Aug 29 2016, Baolin Wang wrote: >>> Hi Felipe, On 11 August 2016 at 11:14, Baolin Wang wrote: > Hi Felipe, > > On 1 August 2016 at 15:09, Baolin Wang wrote: >> Currently the Linux kernel does not provide any standard integration of >> this >> feature that integrates the USB subsystem with the system power >> regulation >> provided by PMICs meaning that either vendors must add this in their >> kernels >> or USB gadget devices based on Linux (such as mobile phones) may not >> behave >> as they should. Thus provide a standard framework for doing this in >> kernel. >> >> Now introduce one user with wm831x_power to support and test the usb >> charger, >> which is pending testing. Moreover there may be other potential users >> will use >> it in future. > > Could you please apply this patchset into your 'next' branch if you > have no comments about it? Thank you. Since there are no other comments about this patchset for a long time, could you please apply this patchset? Thanks. >>> >> >> Sorry for the late reply. >> >>> Sorry, I should have replied earlier. Tim Bird mentioned on the >>> ksummit-discuss list that there was a frustration with this not making >>> progress so I decided to contribute what I could now. >>> >>> I think this patch set is attempting to address an important problem >>> that needs solving. However I think it gets some key aspects wrong. >>> Maybe they can get fixed up after the patchset is upstream, maybe they >>> should be fixed first - I have no strong opinion on that. >>> >>> My main complaints involve the detection and handling of the different >>> charger types - DCP, CDP, ACA etc. >>> The big-picture requirement here that the PHY will detect the physical >>> properties of the cable (e.g. resistance to ground on ID) and determine >>> the type of charger expected. This information must be communicated to >>> the PMIC "power_supply" device so it can regulate the power being drawn >>> through the cable. >>> >>> The first problem is that there are two different ways that the >>> distinction between DCP, CDP, ACA etc can be represented in Linux. They >>> are cable types in the 'extcon' subsystem, and they are power_supply >>> types in the 'power_supply' subsystem. This duplication is confusing. >>> It is not caused by your patch set, but I believe your patchset needs to >>> work with the duplication and I think it does so poorly. >> >> Now the usb charger will not get charger type from 'extcon' subsystem, >> we get the charger type from 'power_supply' and calllback >> 'get_charger_type' for users. > > I understand this. I think it is wrong because, in general, the > power_supply doesn't know what the charger_type is (it might know it is > USB, but most don't know which sort of USB). The PHY knows that, not > the power_supply. I don't think so. Now many platforms will detect the charger type by PMIC hardware, and we can get the charger type by PMIC hardware register. Then power supply driver can access the PMIC register to get the charger type. Here USB charger just considers if the accessing the PMIC register to get charger type is implemented in power supply, it is optional depending on what your platform designed. >> >>> >>> In my mind, the power_supply should *not* know about this distinction at >>> all (except possibly as an advisor attribute simiarly to the current >>> battery technology attribute). The other types it knows of are "AC", >>> "USB", and "BATTERY". The contrast between these is quite different >>> From the contrast between DCP, CDP, ACA, which, from the perspective of >>> the power supply, are almost irrelevant. Your patchset effectively >>> examines the power_supply_type of one power_supply, and communicates it >>> to another. It isn't clear to me how the first power_supply gets the >>> information, or what the relationship between the two power_supplies is >>> meant to be. >> >> We just get the charger type from the power supply which can get the >> charger type from register or something else, > > But that register would be part of the PHY, not part of the charger. > Having the power_supply driver reading the PHY register might work for > some hardware, but is not a general solution. Not only PHY. Like I said, the charger type detection can be done by PMIC hardware, power supply can get the charger type by accessing PMIC registers. >>and the usb charger did >> nothing for this power supply. In some platform, the charger type is >> get in power supply driver, thus we should link this power supply to >> get the charger type when USB
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
On Thu, Sep 08 2016, Baolin Wang wrote: > Hi Neil, > > On 6 September 2016 at 13:40, NeilBrownwrote: >> On Mon, Aug 29 2016, Baolin Wang wrote: >> >>> Hi Felipe, >>> >>> On 11 August 2016 at 11:14, Baolin Wang wrote: Hi Felipe, On 1 August 2016 at 15:09, Baolin Wang wrote: > Currently the Linux kernel does not provide any standard integration of > this > feature that integrates the USB subsystem with the system power regulation > provided by PMICs meaning that either vendors must add this in their > kernels > or USB gadget devices based on Linux (such as mobile phones) may not > behave > as they should. Thus provide a standard framework for doing this in > kernel. > > Now introduce one user with wm831x_power to support and test the usb > charger, > which is pending testing. Moreover there may be other potential users > will use > it in future. Could you please apply this patchset into your 'next' branch if you have no comments about it? Thank you. >>> >>> Since there are no other comments about this patchset for a long time, >>> could you please apply this patchset? Thanks. >> > > Sorry for the late reply. > >> Sorry, I should have replied earlier. Tim Bird mentioned on the >> ksummit-discuss list that there was a frustration with this not making >> progress so I decided to contribute what I could now. >> >> I think this patch set is attempting to address an important problem >> that needs solving. However I think it gets some key aspects wrong. >> Maybe they can get fixed up after the patchset is upstream, maybe they >> should be fixed first - I have no strong opinion on that. >> >> My main complaints involve the detection and handling of the different >> charger types - DCP, CDP, ACA etc. >> The big-picture requirement here that the PHY will detect the physical >> properties of the cable (e.g. resistance to ground on ID) and determine >> the type of charger expected. This information must be communicated to >> the PMIC "power_supply" device so it can regulate the power being drawn >> through the cable. >> >> The first problem is that there are two different ways that the >> distinction between DCP, CDP, ACA etc can be represented in Linux. They >> are cable types in the 'extcon' subsystem, and they are power_supply >> types in the 'power_supply' subsystem. This duplication is confusing. >> It is not caused by your patch set, but I believe your patchset needs to >> work with the duplication and I think it does so poorly. > > Now the usb charger will not get charger type from 'extcon' subsystem, > we get the charger type from 'power_supply' and calllback > 'get_charger_type' for users. I understand this. I think it is wrong because, in general, the power_supply doesn't know what the charger_type is (it might know it is USB, but most don't know which sort of USB). The PHY knows that, not the power_supply. > >> >> In my mind, the power_supply should *not* know about this distinction at >> all (except possibly as an advisor attribute simiarly to the current >> battery technology attribute). The other types it knows of are "AC", >> "USB", and "BATTERY". The contrast between these is quite different >> From the contrast between DCP, CDP, ACA, which, from the perspective of >> the power supply, are almost irrelevant. Your patchset effectively >> examines the power_supply_type of one power_supply, and communicates it >> to another. It isn't clear to me how the first power_supply gets the >> information, or what the relationship between the two power_supplies is >> meant to be. > > We just get the charger type from the power supply which can get the > charger type from register or something else, But that register would be part of the PHY, not part of the charger. Having the power_supply driver reading the PHY register might work for some hardware, but is not a general solution. >and the usb charger did > nothing for this power supply. In some platform, the charger type is > get in power supply driver, thus we should link this power supply to > get the charger type when USB cable is plugin. If you don't get > charger type from power supply driver, then it does not need to link > this power supply phandle. > >> >> It makes much more sense, to me, to utilized the knowledge of this >> distinction that extcon provides. A usb PHY can register an extcon, >> declare the sorts of cables that it can detect, and tell the extcon as >> cables appear or disappear. The PMIC power_supply can then register with >> that extcon for events and can find out when a cable is attached, and >> what sort of cable. >> Your usb-charging framework would be well placed to help the >> power_supply to find the correct extcon, and possibly even to handle the >> registration for events. >> >> Your framework does
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
Hi Neil, On 6 September 2016 at 13:40, NeilBrownwrote: > On Mon, Aug 29 2016, Baolin Wang wrote: > >> Hi Felipe, >> >> On 11 August 2016 at 11:14, Baolin Wang wrote: >>> Hi Felipe, >>> >>> On 1 August 2016 at 15:09, Baolin Wang wrote: Currently the Linux kernel does not provide any standard integration of this feature that integrates the USB subsystem with the system power regulation provided by PMICs meaning that either vendors must add this in their kernels or USB gadget devices based on Linux (such as mobile phones) may not behave as they should. Thus provide a standard framework for doing this in kernel. Now introduce one user with wm831x_power to support and test the usb charger, which is pending testing. Moreover there may be other potential users will use it in future. >>> >>> Could you please apply this patchset into your 'next' branch if you >>> have no comments about it? Thank you. >> >> Since there are no other comments about this patchset for a long time, >> could you please apply this patchset? Thanks. > Sorry for the late reply. > Sorry, I should have replied earlier. Tim Bird mentioned on the > ksummit-discuss list that there was a frustration with this not making > progress so I decided to contribute what I could now. > > I think this patch set is attempting to address an important problem > that needs solving. However I think it gets some key aspects wrong. > Maybe they can get fixed up after the patchset is upstream, maybe they > should be fixed first - I have no strong opinion on that. > > My main complaints involve the detection and handling of the different > charger types - DCP, CDP, ACA etc. > The big-picture requirement here that the PHY will detect the physical > properties of the cable (e.g. resistance to ground on ID) and determine > the type of charger expected. This information must be communicated to > the PMIC "power_supply" device so it can regulate the power being drawn > through the cable. > > The first problem is that there are two different ways that the > distinction between DCP, CDP, ACA etc can be represented in Linux. They > are cable types in the 'extcon' subsystem, and they are power_supply > types in the 'power_supply' subsystem. This duplication is confusing. > It is not caused by your patch set, but I believe your patchset needs to > work with the duplication and I think it does so poorly. Now the usb charger will not get charger type from 'extcon' subsystem, we get the charger type from 'power_supply' and calllback 'get_charger_type' for users. > > In my mind, the power_supply should *not* know about this distinction at > all (except possibly as an advisor attribute simiarly to the current > battery technology attribute). The other types it knows of are "AC", > "USB", and "BATTERY". The contrast between these is quite different > From the contrast between DCP, CDP, ACA, which, from the perspective of > the power supply, are almost irrelevant. Your patchset effectively > examines the power_supply_type of one power_supply, and communicates it > to another. It isn't clear to me how the first power_supply gets the > information, or what the relationship between the two power_supplies is > meant to be. We just get the charger type from the power supply which can get the charger type from register or something else, and the usb charger did nothing for this power supply. In some platform, the charger type is get in power supply driver, thus we should link this power supply to get the charger type when USB cable is plugin. If you don't get charger type from power supply driver, then it does not need to link this power supply phandle. > > It makes much more sense, to me, to utilized the knowledge of this > distinction that extcon provides. A usb PHY can register an extcon, > declare the sorts of cables that it can detect, and tell the extcon as > cables appear or disappear. The PMIC power_supply can then register with > that extcon for events and can find out when a cable is attached, and > what sort of cable. > Your usb-charging framework would be well placed to help the > power_supply to find the correct extcon, and possibly even to handle the > registration for events. > > Your framework does currently register with extcon, but only listens for > EXTCON_USB cables. I don't think that cable type is (reliably) reported > when a DCP (for example) is plugged in. Here we just listen the plugin/out events from extcon, if one cable plugin it will report to usb charger. > > Here there is another problem that is not of your making, but still > needs fixing. Extcon declares a number of cable types like: > > /* USB external connector */ > #define EXTCON_USB 1 > #define EXTCON_USB_HOST 2 > > /* Charging external connector */ > #define EXTCON_CHG_USB_SDP 5 /* Standard Downstream Port */
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
Hi, NeilBrownwrites: > Firstly, you have made the current limit associated with each cable type > configurable (__usb_charger_set_cur_limit_by_type). This is nonsense. > The standard (e.g. BC-1.2) declares what the current limits are. There > is no reason for those not to be hard coded. I had raised the same concern WRT configuration current limits. > Secondly, you treat each charger type as having a single "cur_limit" and > utilize that limit by telling the PMIC to draw that much current. > Again, this is inconsistent with the specification. > BC-1.2 defines, for each charger type, a minimum and maximum current > level. > The minimum should always be available. Attempting to draw more than > that (but less that the max) might work or might cause the charger > to shut down, but you can be sure that the charger will respond to the > increased load by first reducing the voltage, and will not shut down > until the voltage has dropped below 2V. > If you try to draw more current than the maximum, then the charger might > shut down before the voltage drops below 2V. Very well put :-) > Given this understanding of the current available from the charger, > there are two approaches the PMIC might take. > 1/ if the PMIC is able to exercise fine control over the current it > draws, and if it can monitor the voltage on the charger, then it > could gradually increase the power being requested until the voltage > drops below some threshold (e.g. 4.75V), and then (probably) back off > a little. It should only increase at most up to the maximum, even if > the voltage remains high. It should probably start at zero rather > than at the minimum. This allows for lossage elsewhere. That's what most charging control SW I've seen in the past ends up doing. Correct > 2/ If the PMIC cannot measure voltage, or doesn't have sufficiently fine >control of the current requested, then it should request only the >minimum available current. Any more is not safe. correct -- balbi signature.asc Description: PGP signature
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
On Mon, Aug 29 2016, Baolin Wang wrote: > Hi Felipe, > > On 11 August 2016 at 11:14, Baolin Wangwrote: >> Hi Felipe, >> >> On 1 August 2016 at 15:09, Baolin Wang wrote: >>> Currently the Linux kernel does not provide any standard integration of this >>> feature that integrates the USB subsystem with the system power regulation >>> provided by PMICs meaning that either vendors must add this in their kernels >>> or USB gadget devices based on Linux (such as mobile phones) may not behave >>> as they should. Thus provide a standard framework for doing this in kernel. >>> >>> Now introduce one user with wm831x_power to support and test the usb >>> charger, >>> which is pending testing. Moreover there may be other potential users will >>> use >>> it in future. >> >> Could you please apply this patchset into your 'next' branch if you >> have no comments about it? Thank you. > > Since there are no other comments about this patchset for a long time, > could you please apply this patchset? Thanks. Sorry, I should have replied earlier. Tim Bird mentioned on the ksummit-discuss list that there was a frustration with this not making progress so I decided to contribute what I could now. I think this patch set is attempting to address an important problem that needs solving. However I think it gets some key aspects wrong. Maybe they can get fixed up after the patchset is upstream, maybe they should be fixed first - I have no strong opinion on that. My main complaints involve the detection and handling of the different charger types - DCP, CDP, ACA etc. The big-picture requirement here that the PHY will detect the physical properties of the cable (e.g. resistance to ground on ID) and determine the type of charger expected. This information must be communicated to the PMIC "power_supply" device so it can regulate the power being drawn through the cable. The first problem is that there are two different ways that the distinction between DCP, CDP, ACA etc can be represented in Linux. They are cable types in the 'extcon' subsystem, and they are power_supply types in the 'power_supply' subsystem. This duplication is confusing. It is not caused by your patch set, but I believe your patchset needs to work with the duplication and I think it does so poorly. In my mind, the power_supply should *not* know about this distinction at all (except possibly as an advisor attribute simiarly to the current battery technology attribute). The other types it knows of are "AC", "USB", and "BATTERY". The contrast between these is quite different From the contrast between DCP, CDP, ACA, which, from the perspective of the power supply, are almost irrelevant. Your patchset effectively examines the power_supply_type of one power_supply, and communicates it to another. It isn't clear to me how the first power_supply gets the information, or what the relationship between the two power_supplies is meant to be. It makes much more sense, to me, to utilized the knowledge of this distinction that extcon provides. A usb PHY can register an extcon, declare the sorts of cables that it can detect, and tell the extcon as cables appear or disappear. The PMIC power_supply can then register with that extcon for events and can find out when a cable is attached, and what sort of cable. Your usb-charging framework would be well placed to help the power_supply to find the correct extcon, and possibly even to handle the registration for events. Your framework does currently register with extcon, but only listens for EXTCON_USB cables. I don't think that cable type is (reliably) reported when a DCP (for example) is plugged in. Here there is another problem that is not of your making, but still needs fixing. Extcon declares a number of cable types like: /* USB external connector */ #define EXTCON_USB 1 #define EXTCON_USB_HOST 2 /* Charging external connector */ #define EXTCON_CHG_USB_SDP 5 /* Standard Downstream Port */ #define EXTCON_CHG_USB_DCP 6 /* Dedicated Charging Port */ #define EXTCON_CHG_USB_CDP 7 /* Charging Downstream Port */ #define EXTCON_CHG_USB_ACA 8 /* Accessory Charger Adapter */ #define EXTCON_CHG_USB_FAST 9 #define EXTCON_CHG_USB_SLOW 10 However it doesn't define what those mean, so we are left to guess. They each correspond to bits in a bitmap, so a cable can have multiple types. I think the best interpretation is that: EXTCON_USB means that the cable carries USB data from a host. EXTCON_USB_HOST means that that cable carries USB data to a host. EXTCON_CHG_* means that power is available as described in the standards. (what EXTCON_CHG_USB_FAST and EXTCON_CHG_USB_SLOW mean is not at all clear). There is some support for this in the code, but it is not universally acknowledged. For a USB charging framework to be genuinely useful, it must (I think) make sure this issue gets clarified, and the
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
Hi Felipe, On 11 August 2016 at 11:14, Baolin Wangwrote: > Hi Felipe, > > On 1 August 2016 at 15:09, Baolin Wang wrote: >> Currently the Linux kernel does not provide any standard integration of this >> feature that integrates the USB subsystem with the system power regulation >> provided by PMICs meaning that either vendors must add this in their kernels >> or USB gadget devices based on Linux (such as mobile phones) may not behave >> as they should. Thus provide a standard framework for doing this in kernel. >> >> Now introduce one user with wm831x_power to support and test the usb charger, >> which is pending testing. Moreover there may be other potential users will >> use >> it in future. > > Could you please apply this patchset into your 'next' branch if you > have no comments about it? Thank you. Since there are no other comments about this patchset for a long time, could you please apply this patchset? Thanks. > >> >> CHanges since v15: >> - Add charger state checking to avoid sending out duplicate notifies to >> users. >> - Add one work to notify power users the current has been changed. >> >> Changes since v14: >> - Add kernel documentation for struct usb_cahrger. >> - Remove some redundant WARN() functions. >> >> Changes since v13: >> - Remove the charger checking in usb_gadget_vbus_draw() function. >> - Rename some functions in charger.c file. >> - Rebase on git://git.kernel.org/pub/scm/linux/kernel/git/balbi/usb.git >> tags/usb-for-v4.8 >> >> Changes since v12: >> - Remove the class and device things. >> - Link usb charger to udc-core.ko. >> - Create one "charger" subdirectory which holds all charger-related >> attributes. >> >> Changes since v11: >> - Reviewed and tested by Li Jun. >> >> Changes since v10: >> - Introduce usb_charger_get_state() function to check charger state. >> - Remove the mutex lock in usb_charger_set_cur_limit_by_type() function >> in case will be issued in atomic context. >> >> Baolin Wang (4): >> usb: gadget: Introduce the usb charger framework >> usb: gadget: Support for the usb charger framework >> usb: gadget: Integrate with the usb gadget supporting for usb charger >> power: wm831x_power: Support USB charger current limit management >> >> drivers/power/wm831x_power.c | 69 >> drivers/usb/gadget/Kconfig |8 + >> drivers/usb/gadget/udc/Makefile |1 + >> drivers/usb/gadget/udc/charger.c | 780 >> ++ >> drivers/usb/gadget/udc/core.c| 17 + >> include/linux/mfd/wm831x/pdata.h |3 + >> include/linux/usb/charger.h | 186 + >> include/linux/usb/gadget.h |3 + >> include/uapi/linux/usb/charger.h | 31 ++ >> 9 files changed, 1098 insertions(+) >> create mode 100644 drivers/usb/gadget/udc/charger.c >> create mode 100644 include/linux/usb/charger.h >> create mode 100644 include/uapi/linux/usb/charger.h >> >> -- >> 1.7.9.5 >> > > > > -- > Baolin.wang > Best Regards -- Baolin.wang Best Regards -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH v16 0/4] Introduce usb charger framework to deal with the usb gadget power negotation
Hi Felipe, On 1 August 2016 at 15:09, Baolin Wangwrote: > Currently the Linux kernel does not provide any standard integration of this > feature that integrates the USB subsystem with the system power regulation > provided by PMICs meaning that either vendors must add this in their kernels > or USB gadget devices based on Linux (such as mobile phones) may not behave > as they should. Thus provide a standard framework for doing this in kernel. > > Now introduce one user with wm831x_power to support and test the usb charger, > which is pending testing. Moreover there may be other potential users will use > it in future. Could you please apply this patchset into your 'next' branch if you have no comments about it? Thank you. > > CHanges since v15: > - Add charger state checking to avoid sending out duplicate notifies to > users. > - Add one work to notify power users the current has been changed. > > Changes since v14: > - Add kernel documentation for struct usb_cahrger. > - Remove some redundant WARN() functions. > > Changes since v13: > - Remove the charger checking in usb_gadget_vbus_draw() function. > - Rename some functions in charger.c file. > - Rebase on git://git.kernel.org/pub/scm/linux/kernel/git/balbi/usb.git > tags/usb-for-v4.8 > > Changes since v12: > - Remove the class and device things. > - Link usb charger to udc-core.ko. > - Create one "charger" subdirectory which holds all charger-related > attributes. > > Changes since v11: > - Reviewed and tested by Li Jun. > > Changes since v10: > - Introduce usb_charger_get_state() function to check charger state. > - Remove the mutex lock in usb_charger_set_cur_limit_by_type() function > in case will be issued in atomic context. > > Baolin Wang (4): > usb: gadget: Introduce the usb charger framework > usb: gadget: Support for the usb charger framework > usb: gadget: Integrate with the usb gadget supporting for usb charger > power: wm831x_power: Support USB charger current limit management > > drivers/power/wm831x_power.c | 69 > drivers/usb/gadget/Kconfig |8 + > drivers/usb/gadget/udc/Makefile |1 + > drivers/usb/gadget/udc/charger.c | 780 > ++ > drivers/usb/gadget/udc/core.c| 17 + > include/linux/mfd/wm831x/pdata.h |3 + > include/linux/usb/charger.h | 186 + > include/linux/usb/gadget.h |3 + > include/uapi/linux/usb/charger.h | 31 ++ > 9 files changed, 1098 insertions(+) > create mode 100644 drivers/usb/gadget/udc/charger.c > create mode 100644 include/linux/usb/charger.h > create mode 100644 include/uapi/linux/usb/charger.h > > -- > 1.7.9.5 > -- Baolin.wang Best Regards -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html