Message-ID: <CAD=FV=UFkTHhsxFZGPqFVOX6ra+bx=1P-jAdh1wz-_Q=GBJc4Q@mail.gmail.com>
Date:   Wed, 13 Sep 2023 09:25:15 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     dri-devel@...ts.freedesktop.org,
        Maxime Ripard <mripard@...nel.org>, airlied@...il.com,
        daniel@...ll.ch, linux-kernel@...r.kernel.org,
        linux-mips@...r.kernel.org
Subject: Re: [RFT PATCH 03/15] drm/ingenic: Call drm_atomic_helper_shutdown()
 at shutdown time

Hi,

On Tue, Sep 5, 2023 at 1:16 PM Doug Anderson <dianders@...omium.org> wrote:
>
> Paul,
>
> On Mon, Sep 4, 2023 at 2:15 AM Paul Cercueil <paul@...pouillou.net> wrote:
> >
> > Hi Douglas,
> >
> > Le vendredi 01 septembre 2023 à 16:41 -0700, Douglas Anderson a écrit :
> > > Based on grepping through the source code this driver appears to be
> > > missing a call to drm_atomic_helper_shutdown() at system shutdown
> > > time. Among other things, this means that if a panel is in use that
> > > it
> > > won't be cleanly powered off at system shutdown time.
> > >
> > > The fact that we should call drm_atomic_helper_shutdown() in the case
> > > of OS shutdown/restart comes straight out of the kernel doc "driver
> > > instance overview" in drm_drv.c.
> > >
> > > Since this driver uses the component model and shutdown happens at
> > > the
> > > base driver, we communicate whether we have to call
> > > drm_atomic_helper_shutdown() by seeing if drvdata is non-NULL.
> > >
> > > Suggested-by: Maxime Ripard <mripard@...nel.org>
> > > Signed-off-by: Douglas Anderson <dianders@...omium.org>
> >
> > LGTM.
> > Acked-by: Paul Cercueil <paul@...pouillou.net>
>
> Thanks for the Ack! Would you expect this patch to land through
> "drm-misc", or do you expect it to go through some other tree?
> Running:
>
> ./scripts/get_maintainer.pl --scm -f drivers/gpu/drm/ingenic/ingenic-drm-drv.c
>
> ...does not show that this driver normally goes through drm-misc, but
> it also doesn't show that it goes through any other tree so maybe it's
> just an artifact of the way it's tagged in the MAINTAINERS file? If
> it's fine for this to go through drm-misc, I'll probably land it (with
> your Ack and Maxime's Review) sooner rather than later just to make
> this patch series less unwieldy.
>
>
> > > ---
> > > This commit is only compile-time tested.
> > >
> > > NOTE: this patch touches a lot more than other similar patches since
> > > the bind() function is long and we want to make sure that we unset
> > > the
> > > drvdata if bind() fails.
> > >
> > > While making this patch, I noticed that the bind() function of this
> > > driver is using "devm" and thus assumes it doesn't need to do much
> > > explicit error handling. That's actually a bug. As per kernel docs
> > > [1]
> > > "the lifetime of the aggregate driver does not align with any of the
> > > underlying struct device instances. Therefore devm cannot be used and
> > > all resources acquired or allocated in this callback must be
> > > explicitly released in the unbind callback". Fixing that is outside
> > > the scope of this commit.
> > >
> > > [1] https://docs.kernel.org/driver-api/component.html
> > >
> >
> > Noted, thanks.
>
> FWIW, I think that at least a few other DRM drivers handle this by
> doing some of their resource allocation / acquiring in the probe()
> function and then only doing things in the bind() that absolutely need
> to be in the bind. ;-)

I've been collecting patches that are ready to land in drm-misc but,
right now, I'm not taking this patch since I didn't get any
clarification of whether it should land through drm-misc or somewhere
else.

-Doug

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