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

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Date: Wed, 17 Jan 2024 10:36:49 -0800
From: Doug Anderson <dianders@...omium.org>
To: Pin-yen Lin <treapking@...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,

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@...omium.org> 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