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

[Stefan Wahren]

Hi,

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?

Best regards

>
> Maxime
>