linux-kernel - Re: [PATCH v2 6/7] drm/i915/dsi: Replace poking of CHV GPIOs behind the driver's back

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Date:   Tue, 31 Oct 2023 17:07:39 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Jani Nikula <jani.nikula@...el.com>,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Cc:     Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH v2 6/7] drm/i915/dsi: Replace poking of CHV GPIOs behind
 the driver's back

Hi Andy,

On 10/24/23 18:11, Andy Shevchenko wrote:
> On Tue, Oct 24, 2023 at 06:57:38PM +0300, Andy Shevchenko wrote:
>> It's a dirty hack in the driver that pokes GPIO registers behind
>> the driver's back. Moreoever it might be problematic as simultaneous
>> I/O may hang the system, see the commit 0bd50d719b00 ("pinctrl:
>> cherryview: prevent concurrent access to GPIO controllers") for
>> the details. Taking all this into consideration replace the hack
>> with proper GPIO APIs being used.
> 
> Ah, just realised that this won't work if it happens to request to GPIOs with
> the same index but different communities. I will fix that in v3, but will wait
> for Hans to test VLV and it might even work in most of the cases on CHV as it
> seems quite unlikely that the above mentioned assertion is going to happen in
> real life.

I have added patches 1-5 to my personal tree + a small debug patch on top
which logs when soc_exec_opaque_gpio() actually gets called.

So these patches will now get run every time I run some tests on
one my tablets.

I'll get back to you with testing results when I've found a device where
the new soc_exec_opaque_gpio() actually gets called.

As for the CHT support, I have not added that to my tree yet, I would
prefer to directly test the correct/fixed patch.

Regards,

Hans