On Thu, Nov 6, 2014 at 11:18 AM, Pankaj Dubey <pankaj.du...@samsung.com> wrote:
> On Wednesday, November 05, 2014 7:18 PM, Sylwester Nawrocki wrote:
>> On 04/11/14 04:18, Pankaj Dubey wrote:
>> > 2: Since PM domain relies on PMU registers and does not have its own
>> > DT binding, MFD client and MFD device is most suitable for making
>> > this kind of platform drivers.
>>
>> We have DT binding for the Exynos power domains:
>> Documentation/devicetree/bindings/arm/exynos/power_domain.txt
>> In fact the IO memory regions used in the power domain bindings fall
>> within the
>> (sparse) PMU registers region.
>>
>
> Correct. But currently there is no platform driver for those DT bindings so
> we have two options:
> 1) Register a new platform driver for each of those DT nodes, which are using
> a very small subset of PMU register region. And we end up getting platform
> driver's probe for each pd nodes.
> 2) Register an Exynos power domain driver which will be a client driver of
> main Exynos PMU driver, and will get platform data from it. And in this probe
> parse all pd device nodes and populate all related information from those
> nodes into Exynos_pm_domain struct instances and keep list of these
> instances. Same has been proposed in Amit's patch.
>
> I would prefer second method, as next, we can move pm sleep functionality
> (which also uses PMU register sets) also into such small mfd client driver.
> And as far as I know for pm sleep currently there is no DT nodes.
>
>> There is also DT binding for the PMU subsystem:
>> Documentation/devicetree/bindings/arm/samsung/pmu.txt
>
> Yes, and currently I have used same binding to convert PMU implementation
> into a platform driver [1]. Now what we trying to address is same PMU
> implementation can be reused for ARM64 based SoC if we have to move it into
> "drivers/mfd/" or "drivers/power/" or may be "drivers/soc".
>
> [1]: http://www.spinics.net/lists/linux-samsung-soc/msg37572.html
>
> Currently we moved into "drivers/mfd" and patches from Amit shows an use case
> where power domain implementation has been converted into platform driver,
> but its probe will be called by MFD subsystem and will not be bind to DT
> nodes of pd as it will be a client device to main PMU device. Please check
> this [2], [3].
>
> [2]: http://www.spinics.net/lists/linux-samsung-soc/msg38446.html
> [3]: http://www.spinics.net/lists/linux-samsung-soc/msg38447.html
>
>>
>> I guess a platform device driver in drivers/power would be a better
>> fit than drivers/mfd. I doubt introducing an mfd driver now makes much
>> sense, we have already DT bindings for PHYs, the power domains, etc.
>>
>
> The reason behind making it a mfd driver is, to make following design for pm
> domain and pm sleep functionality.
> ----------------------
> | Exynos - PMU |
> | MFD device |
> | drivers/mfd/ |
> ------------------------
> |
> -----------------------------------------------
> | |
> -------------------------------
> ------------------------------------
> | Exynos -pd | | Exynos - pm-sleep
> |
> | PMU's client device | | PMU's client device |
> | (drivers/soc/samsung/) | | (drivers/soc/samsung/) |
> --------------------------------
> ---------------------------------
I will post this sleep driver shortly. I also suggest to keep
everything in drivers/soc/samsung as all these drivers very much SoC
specific.
>
> As Lee mentioned MFD can be used to register the device ( I am assuming he is
> referring to use of " mfd_add_devices" from Exynos -PMU driver, to make it a
> mfd device) but it should be kept outside of "drivers/mfd". I just looked for
> current users of "mfd_add_devices" but only drivers from "drivers/mfd" only
> are calling this API, also once we call this API it will become an MFD device
> then why not keep into "drivers/mfd" or maybe I have little understanding of
> purpose of "drivers/mfd".
>
> But still if it's OK to register Exynos -PMU as MFD device even if it's not
> in "drivers/mfd" folder, then I would suggest better to keep it in
> "drivers/soc/samsung/" as it's very much SoC specific. As "drivers/power"
> looks like place to keep external power supply drivers such as batteries, AC,
> USB etc.
>
> Thanks,
> Pankaj Dubey
>
>> --
>> Thanks,
>> Sylwester
>
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