linux-kernel - Re: [PATCH v2] drm/bridge: parade-ps8640: Ensure bridge is suspended in .post

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Date: Thu, 18 Jan 2024 11:25:09 +0800
From: Pin-yen Lin <treapking@...omium.org>
To: Doug Anderson <dianders@...omium.org>
Cc: Andrzej Hajda <andrzej.hajda@...el.com>, Neil Armstrong <neil.armstrong@...aro.org>, 
	Robert Foss <rfoss@...nel.org>, Laurent Pinchart <Laurent.pinchart@...asonboard.com>, 
	Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>, 
	dri-devel@...ts.freedesktop.org, Sean Paul <seanpaul@...omium.org>, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] drm/bridge: parade-ps8640: Ensure bridge is suspended
 in .post_disable()

Hi Doug,

On Thu, Jan 18, 2024 at 2:37 AM Doug Anderson <dianders@...omium.org> wrote:
>
> Hi,
>
> On Wed, Jan 17, 2024 at 9:34 AM Doug Anderson <dianders@...omium.org> wrote:
> >
> > Hi,
> >
> > On Tue, Jan 9, 2024 at 8:52 AM Doug Anderson <dianders@...omiumorg> wrote:
> > >
> > > Hi,
> > >
> > > On Tue, Jan 9, 2024 at 4:05 AM Pin-yen Lin <treapking@...omium.org> wrote:
> > > >
> > > > The ps8640 bridge seems to expect everything to be power cycled at the
> > > > disable process, but sometimes ps8640_aux_transfer() holds the runtime
> > > > PM reference and prevents the bridge from suspend.
> > > >
> > > > Prevent that by introducing a mutex lock between ps8640_aux_transfer()
> > > > and .post_disable() to make sure the bridge is really powered off.
> > > >
> > > > Fixes: 826cff3f7ebb ("drm/bridge: parade-ps8640: Enable runtime power management")
> > > > Signed-off-by: Pin-yen Lin <treapking@...omium.org>
> > > > ---
> > > >
> > > > Changes in v2:
> > > > - Use mutex instead of the completion and autosuspend hack
> > > >
> > > >  drivers/gpu/drm/bridge/parade-ps8640.c | 16 ++++++++++++++++
> > > >  1 file changed, 16 insertions(+)
> > >
> > > This looks OK to me now.
> > >
> > > Reviewed-by: Douglas Anderson <dianders@...omium.org>
> > >
> > > I'll let it stew on the mailing list for ~1 week and then land it in
> > > drm-misc-fixes unless there are additional comments.
> >
> > Pushed to drm-misc-fixes:
> >
> > 26db46bc9c67 drm/bridge: parade-ps8640: Ensure bridge is suspended in
> > .post_disable()
>
> Crud. I landed this and then almost immediately hit a bug with it. :(
> I've posted up the fix:
>
> https://lore.kernel.org/r/20240117103502.1.Ib726a0184913925efc7e99c4d4fc801982e1bc24@changeid
>
> -Doug

Sorry, I missed this because the patch was based on drm-misc-next, so
it did not include commit 024b32db43a3 ("drm/bridge: parade-ps8640:
Wait for HPD when doing an AUX transfer").

I also forgot to apply that commit when I did my testing.

Pin-yen