[PATCH RFC] drm/vc4: hdmi: Fix connector detect logic

[Stefan Wahren]

Hi Maxime,

Am 06.07.21 um 15:21 schrieb Maxime Ripard:
> Hi Stefan,
>
> On Tue, Jul 06, 2021 at 12:48:05PM +0200, Stefan Wahren wrote:
>> Am 06.07.21 um 11:58 schrieb Maxime Ripard:
>>> Hi,
>>>
>>> On Mon, Jul 05, 2021 at 11:36:34PM +0200, Stefan Wahren wrote:
>>>> Commit "drm/vc4: hdmi: Convert to gpiod" changes the behavior of
>>>> vc4_hdmi_connector_detect() which results into CPU hangs in case there
>>>> is no HDMI connected. Let's restore the old behavior.
>>>>
>>>> Reported-by: Nathan Chancellor <nathan at kernel.org>
>>>> Reported-by: Ojaswin Mujoo <ojaswin98 at gmail.com>
>>>> Fixes: 6800234ceee0 ("drm/vc4: hdmi: Convert to gpiod")
>>>> Signed-off-by: Stefan Wahren <stefan.wahren at i2se.com>
>>> I already sent this patch last week:
>>>
>>> https://lore.kernel.org/dri-devel/20210628124257.140453-3-maxime@cerno.tech/
>> oops, i only looked in the July archive.
>>
>>> I'm not entirely sure how this could create a CPU hang though. Withouth
>>> this patch, if the HPD GPIO is low, we would first try to retrieve the
>>> EDID, and then if it doesn't we would read the hotplug register.
>> Yes, the real issue has been revealed by the original change and this
>> patch only "hides" it again.
>>> The first is using a separate i2c controller (and even if it was in the
>>> same power domain, we have the pm_runtime_resume call), and the register
>>> read should be fine too?
>> Sorry, i don't have a clue and time for further investigations.
>>
>> Does it mean, you are not able to reproduce this issue?
> On next-20210706 at least it works fine for me without an HDMI monitor
> connected, yes:

which configuration do you use? Did you tried arm/multi_v7_defconfig?

I tried yesterday mainline ("a180bd1d7e16173d965b263c5a536aa40afa2a2a")
with multi_v7_defconfig and the issue was there.