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

[Maxime Ripard]

On Tue, Jul 06, 2021 at 05:45:27PM +0200, Stefan Wahren wrote:
> 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.

I can't boot multi_v7_defconfig on my setup, but I just tested multi_v7
+ a few options (UART, ethernet) built-in to be able to boot, and I
can't reproduce what you're seeing. It boots just fine without any
monitor attached.

Maxime
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