linux-kernel - Re: [PATCH v1 1/1] platform/x86/intel: atomisp2: Replace deprecated UNIVERSAL_DEV_PM

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Date: Wed, 10 Apr 2024 13:00:21 +0200
From: Hans de Goede <hdegoede@...hat.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
 Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Subject: Re: [PATCH v1 1/1] platform/x86/intel: atomisp2: Replace deprecated
 UNIVERSAL_DEV_PM_OPS()

Hi,

On 4/9/24 7:15 PM, Andy Shevchenko wrote:
> On Mon, Apr 08, 2024 at 06:20:03PM +0200, Hans de Goede wrote:
>> On 4/3/24 12:55 PM, Andy Shevchenko wrote:
> 
> ...
> 
>> As mentioned in the description of DEFINE_RUNTIME_DEV_PM_OPS()
>> DEFINE_RUNTIME_DEV_PM_OPS() is NOT a 1:1 replacement for
>> UNIVERSAL_DEV_PM_OPS() specifically it uses pm_runtime_force_suspend() /
>> pm_runtime_force_resume() .
> 
> Right.
> 
>> Specifically pm_runtime_force_suspend() may NOT get set (and in this case
>> will not set) needs_force_resume skipping a resume + suspend cycle
>> after a system suspend, which is a problem if firmware has touched
>> the state of the device during the suspend/resume cycle since the device
>> may now actually be left powered on.
> 
> I see, thanks for explaining me this. So this driver is kinda very special.
> Still the old question, can we get rid altogether of these atomisp "drivers"
> in PDx86?

At some time in the future yes. I've recently done some improvements to
the staging atomisp driver so that it will run in a pm-only mode when
the firmware is missing so that the ISP still gets turned off properly
in this case and the driver now supports both BYT + CHT in a single
build so in a way it is ready to replace the atomisp2 pm driver.

But it is still in staging, so distros are unlikely to enable it
and without a atomisp2-pm driver the battery drains much to quickly
especially when suspended.

So I think we are getting there, but now is not the right moment
to drop this driver.

>> It seems there is no direct replacement for UNIVERSAL_DEV_PM_OPS()
>> without a behavior change.
> 
> Correct.
> 
> ...
> 
> Btw, have you seen a few cleanup patches against AtomISP v2 by me?

Yes I have a bit of a backlog, I have just processed them,
thank you for those patches.

Regards,

Hans