[PATCH 23/33] drm/vc4: hdmi: Move HDMI reset to pm_resume

[Florian Fainelli]

On 8/15/22 07:12, Maxime Ripard wrote:
> On Wed, Aug 10, 2022 at 10:33:48PM +0200, Stefan Wahren wrote:
>> Hi Florian,
>>
>> Am 09.08.22 um 21:02 schrieb Florian Fainelli:
>>> On 8/4/22 16:11, Florian Fainelli wrote:
>>>> On 6/13/22 07:47, Maxime Ripard wrote:
>>>>> From: Dave Stevenson <dave.stevenson at raspberrypi.com>
>>>>>
>>>>> The BCM2835-37 found in the RaspberryPi 0 to 3 have a power domain
>>>>> attached to the HDMI block, handled in Linux through runtime_pm.
>>>>>
>>>>> That power domain is shared with the VEC block, so even if we put our
>>>>> runtime_pm reference in the HDMI driver it would keep being on. If the
>>>>> VEC is disabled though, the power domain would be disabled and we would
>>>>> lose any initialization done in our bind implementation.
>>>>>
>>>>> That initialization involves calling the reset function and
>>>>> initializing
>>>>> the CEC registers.
>>>>>
>>>>> Let's move the initialization to our runtime_resume implementation so
>>>>> that we initialize everything properly if we ever need to.
>>>>>
>>>>> Fixes: c86b41214362 ("drm/vc4: hdmi: Move the HSM clock enable
>>>>> to runtime_pm")
>>>>> Signed-off-by: Dave Stevenson <dave.stevenson at raspberrypi.com>
>>>>> Signed-off-by: Maxime Ripard <maxime at cerno.tech>
>>>>
>>>> After seeing the same warning as Stefan reported in the link below,
>>>> but on the Raspberry Pi 4B:
>>>>
>>>> https://www.spinics.net/lists/dri-devel/msg354170.html
>>>>
>>>> a separate bisection effort led me to this commit, before is fine,
>>>> after produces 4 warnings during boot, see attached log.
>>>>
>>>> Is there a fix that we can try that would also cover the Raspberry
>>>> Pi 4B? Is it possible that this series precipitates the problem:
>>>>
>>>> https://www.spinics.net/lists/arm-kernel/msg984638.html
>>>
>>> Maxime, Dave, anything you would want me to try? Still seeing these
>>> warnings with net-next-6.0-11220-g15205c2829ca
>>
>> At first this issue doesn't occur in Linux 5.19. So it's something new. I
>> was able to reproduce with todays linux-next, but interestingly it doesn't
>> occur in drm-misc-next.
> 
> Yeah, it should be fixed by
> https://lore.kernel.org/all/20220629123510.1915022-38-maxime@cerno.tech/
> https://lore.kernel.org/all/20220629123510.1915022-39-maxime@cerno.tech/
> 
> Both patches apparently didn't make the cut for the merge window, if it
> works for you we can always queue them in drm-misc-fixes

Both of these patches eliminate the warning, I don't have a good set-up 
yet for ensuring that HDMI/V3dD is functional however:

Tested-by: Florian Fainelli <f.fainelli at gmail.com>
-- 
Florian