Hi, Jun Li <[email protected]> writes: >> -----Original Message----- >> From: Baolin Wang [mailto:[email protected]] >> Sent: Wednesday, March 30, 2016 5:31 PM >> To: Jun Li <[email protected]> >> Cc: Peter Chen <[email protected]>; Felipe Balbi <[email protected]>; >> Greg KH <[email protected]>; Sebastian Reichel <[email protected]>; >> Dmitry Eremin-Solenikov <[email protected]>; David Woodhouse >> <[email protected]>; Peter Chen <[email protected]>; Alan Stern >> <[email protected]>; [email protected]; Yoshihiro Shimoda >> <[email protected]>; Lee Jones <[email protected]>; Mark >> Brown <[email protected]>; Charles Keepax >> <[email protected]>; [email protected]; >> Linux PM list <[email protected]>; USB <[email protected]>; >> [email protected]; LKML <linux- >> [email protected]> >> Subject: Re: [PATCH v8 0/4] Introduce usb charger framework to deal with >> the usb gadget power negotation >> >> On 30 March 2016 at 16:07, Jun Li <[email protected]> wrote: >> > Hi >> >> >> On 30 March 2016 at 10:54, Jun Li <[email protected]> wrote: >> >> >> >> It is not for udc driver but for power users who want to >> >> >> >> negotiate with USB subsystem. >> >> >> >> >> >> >> > >> >> >> > Seems you don't want to guarantee charger type detection is done >> >> >> > before gadget connection(pullup DP), right? >> >> >> > I see you call usb_charger_detect_type() in each gadget usb >> >> >> > state >> >> >> changes. >> >> >> >> >> >> I am not sure I get your point correctly, please correct me if I >> >> >> misunderstand you. >> >> >> We need to check the charger type at every event comes from the >> >> >> usb gadget state changes or the extcon device state changes, which >> >> >> means a new charger plugin or pullup. >> >> >> >> >> > >> >> > According to usb charger spec, my understanding is you can't do >> >> > real charger detection procedure *after* gadget _connection_(pullup >> >> > DP), also I don't >> >> >> >> Why can not? Charger detection is usually from PMIC. >> > >> > Charger detection process will impact DP/DM line state, see usb >> > charger spec v1.2 for detail detection process, section 4.6.3 says: >> > >> > "A PD is allowed to *disconnect* and repeat the charger detection >> > process multiple times while attached. The PD is required to wait for >> > a time of at least TCP_VDM_EN max between disconnecting and restarting >> > the charger detection process." >> > >> > As Peter mentioned, the charger detection should happen between VBUS >> > detection and gadget pull up DP for first plug in case. So when&after >> > gadget connect (pullup DP), you should already know the charger type. >> >> Make sense. In our company's solution, charger detection can be done by >> hardware from PMIC at first, then it will not affect the DP/DM line when >> gadget starts to enumeration. > > I see, charger type detection is done automatically by PMIC when VBUS > is detected in your case, you just assume the process is complete
assuming this finishes before gadget starts is a bad idea. It would've been much more robust to delay usb_gadget_connect() until we KNOW charger detection has completed. -- balbi
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