linux-kernel - Re: [RFT PATCH 13/15] drm/imx/ipuv3: Call drm_atomic_helper

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Message-ID: <CAD=FV=XJ=O5oMKcBSh0qD=ZXUpRgvV8HCheABL7s-T_u+6TsHg@mail.gmail.com>
Date:   Wed, 6 Sep 2023 07:30:48 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Philipp Zabel <p.zabel@...gutronix.de>
Cc:     dri-devel@...ts.freedesktop.org,
        Maxime Ripard <mripard@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>, airlied@...il.com,
        daniel@...ll.ch, festevam@...il.com, kernel@...gutronix.de,
        linux-arm-kernel@...ts.infradead.org, linux-imx@....com,
        linux-kernel@...r.kernel.org, shawnguo@...nel.org
Subject: Re: [RFT PATCH 13/15] drm/imx/ipuv3: Call drm_atomic_helper_shutdown()
 at shutdown/unbind time

Hi,

On Tue, Sep 5, 2023 at 10:47 PM Philipp Zabel <p.zabel@...gutronix.de> wrote:
>
> Hi,
>
> On Di, 2023-09-05 at 13:29 -0700, Doug Anderson wrote:
> > Hi,
> >
> > On Mon, Sep 4, 2023 at 1:30 AM Philipp Zabel <p.zabel@...gutronix.de> wrote:
> > >
> > > On Fr, 2023-09-01 at 16:41 -0700, Douglas Anderson wrote:
> > > > Based on grepping through the source code this driver appears to be
> > > > missing a call to drm_atomic_helper_shutdown() at system shutdown time
> > > > and at driver unbind 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 and at driver remove (or unbind) time comes
> > > > straight out of the kernel doc "driver instance overview" in
> > > > drm_drv.c.
> > > >
> > > > A few notes about this fix:
> > > > - When adding drm_atomic_helper_shutdown() to the unbind path, I added
> > > >   it after drm_kms_helper_poll_fini() since that's when other drivers
> > > >   seemed to have it.
> > > > - Technically with a previous patch, ("drm/atomic-helper:
> > > >   drm_atomic_helper_shutdown(NULL) should be a noop"), we don't
> > > >   actually need to check to see if our "drm" pointer is NULL before
> > > >   calling drm_atomic_helper_shutdown(). We'll leave the "if" test in,
> > > >   though, so that this patch can land without any dependencies. It
> > > >   could potentially be removed later.
> > > > - This patch also makes sure to set the drvdata to NULL in the case of
> > > >   bind errors to make sure that shutdown can't access freed data.
> > > >
> > > > Suggested-by: Maxime Ripard <mripard@...nel.org>
> > > > Signed-off-by: Douglas Anderson <dianders@...omium.org>
> > >
> > > Thank you,
> > > Tested-by: Philipp Zabel <p.zabel@...gutronix.de>
> >
> > Thanks! I notice that:
> >
> > ./scripts/get_maintainer.pl --scm -f drivers/gpu/drm/imx/ipuv3/imx-drm-core.c
> >
> > Doesn't say drm-misc but also when I look at the MAINTAINERS file and
> > find the section for "DRM DRIVERS FOR FREESCALE IMX"
>
> That should probably say "IMX5/6" nowadays. There are a lot more i.MX
> that do not use IPUv3 than those that do.
>
> > it doesn't explicitly list a different git tree.
>
> I used to send pull requests from git.pengutronix.de/git/pza/linux,
> same as for the reset controller framework. I might still have to do
> that for changes in drivers/gpu/ipu-v3 that need coordination between
> drm and v4l2, but usually pure drm/imx/ipuv3 changes are pushed to drm-
> misc.
>
> > I guess the "shawnguo" git tree listed by get_maintainer.pl is just
> > from regex matching?
>
> The "N: imx" pattern in "ARM/FREESCALE IMX / MXC ARM ARCHITECTURE", I
> think.
>
> > Would you expect this to go through drm-misc? If so, I'll probably
> > land it sooner rather than later. I can also post up a patch making it
> > obvious that "DRM DRIVERS FOR FREESCALE IMX" goes through drm-misc if
> > you don't object.
>
> Yes, both would be great.

Maintainers update posted at:

https://lore.kernel.org/r/20230906072803.1.Idef7e77e8961cbeb8625183eec9db0356b2eccd0@changeid

I'll aim to land ${SUBJECT} patch early next week unless there are any
objections.

-Doug