Re: [PATCH v2 1/2] pwm: lpss: platform: Save/restore the ctrl register over a suspend/resume

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On Mon, May 14, 2018 at 1:50 PM, Thierry Reding
<thierry.reding@xxxxxxxxx> wrote:
> On Thu, May 10, 2018 at 05:25:10PM +0200, Rafael J. Wysocki wrote:
>> On Thursday, April 26, 2018 2:10:23 PM CEST Hans de Goede wrote:
>> > On some devices the contents of the ctrl register get lost over a
>> > suspend/resume and the PWM comes back up disabled after the resume.
>> >
>> > This is seen on some Bay Trail devices with the PWM in ACPI enumerated
>> > mode, so it shows up as a platform device instead of a PCI device.
>> >
>> > If we still think it is enabled and then try to change the duty-cycle
>> > after this, we end up with a "PWM_SW_UPDATE was not cleared" error and
>> > the PWM is stuck in that state from then on.
>> >
>> > This commit adds suspend and resume pm callbacks to the pwm-lpss-platform
>> > code, which save/restore the ctrl register over a suspend/resume, fixing
>> > this.
>> >
>> > Note that:
>> >
>> > 1) There is no need to do this over a runtime suspend, since we
>> > only runtime suspend when disabled and then we properly set the enable
>> > bit and reprogram the timings when we re-enable the PWM.
>> >
>> > 2) This may be happening on more systems then we realize, but has been
>> > covered up sofar by a bug in the acpi-lpss.c code which was save/restoring
>> > the regular device registers instead of the lpss private registers due to
>> > lpss_device_desc.prv_offset not being set. This is fixed by a later patch
>> > in this series.
>> >
>> > Cc: stable@xxxxxxxxxxxxxxx
>> > Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
>>
>> Andy, Thierry, any comments or concerns regarding this series?
>
> Hans said in the cover letter of the first version of this series that
> he preferred to merge both patches through the PWM tree because of the
> dependency. So I'm waiting for an Acked-by from you on the ACPI bits.

OK, please feel free to add it to the patches, then.

Thanks,
Rafael



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