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

[Thierry Reding <thierry.reding@gmail.com>]

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On Thu, Apr 26, 2018 at 02:10:23PM +0200, 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@vger.kernel.org
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
> Changes in v2:
> -Add Cc: stable@vger.kernel.org to make sure this goes into stable
>  together with "ACPI / LPSS: Add missing prv_offset setting for byt/cht
>  PWM devices" which depends on this
> ---
>  drivers/pwm/pwm-lpss-platform.c |  5 +++++
>  drivers/pwm/pwm-lpss.c          | 30 ++++++++++++++++++++++++++++++
>  drivers/pwm/pwm-lpss.h          |  2 ++
>  3 files changed, 37 insertions(+)

Applied, thanks.

Thierry

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