linux-kernel - Re: [RFT PATCH v2 09/12] drm/exynos: Call drm_atomic_helper

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Message-ID: <CAD=FV=V2JSHsrTfdxP4=-nU4GGZB999iAb+NU3en-4o3-rLmYQ@mail.gmail.com>
Date:   Fri, 6 Oct 2023 06:50:49 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Inki Dae <daeinki@...il.com>
Cc:     Marek Szyprowski <m.szyprowski@...sung.com>,
        dri-devel@...ts.freedesktop.org,
        Maxime Ripard <mripard@...nel.org>,
        linux-samsung-soc@...r.kernel.org, alim.akhtar@...sung.com,
        sw0312.kim@...sung.com, krzysztof.kozlowski@...aro.org,
        linux-kernel@...r.kernel.org, kyungmin.park@...sung.com,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFT PATCH v2 09/12] drm/exynos: Call drm_atomic_helper_shutdown()
 at shutdown/unbind time

Hi,

On Thu, Oct 5, 2023 at 7:20 PM Inki Dae <daeinki@...il.com> wrote:
>
> Thanks for testing. :)
>
> Acked-by : Inki Dae <inki.dae@...sung.com>

Inki: does that mean you'd like this to go through drm-misc? I'm happy
to do that, but there are no dependencies here so this could easily go
through your tree.


> 2023년 9월 22일 (금) 오후 3:00, Marek Szyprowski <m.szyprowski@...sung.com>님이 작성:
> >
> >
> > On 21.09.2023 21:26, 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>
> > > Reviewed-by: Maxime Ripard <mripard@...nel.org>
> > > Signed-off-by: Douglas Anderson <dianders@...omium.org>
> >
> > Seems to be working fine on all my test Exynos-based boards with display.
> >
> > Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>
> >
> > Reviewed-by: Marek Szyprowski <m.szyprowski@...sung.com>
> >
> > > ---
> > > This commit is only compile-time tested.
> > >
> > > (no changes since v1)
> > >
> > >   drivers/gpu/drm/exynos/exynos_drm_drv.c | 11 +++++++++++
> > >   1 file changed, 11 insertions(+)
> > >
> > > diff --git a/drivers/gpu/drm/exynos/exynos_drm_drv.c b/drivers/gpu/drm/exynos/exynos_drm_drv.c
> > > index 8399256cb5c9..5380fb6c55ae 100644
> > > --- a/drivers/gpu/drm/exynos/exynos_drm_drv.c
> > > +++ b/drivers/gpu/drm/exynos/exynos_drm_drv.c
> > > @@ -300,6 +300,7 @@ static int exynos_drm_bind(struct device *dev)
> > >       drm_mode_config_cleanup(drm);
> > >       exynos_drm_cleanup_dma(drm);
> > >       kfree(private);
> > > +     dev_set_drvdata(dev, NULL);
> > >   err_free_drm:
> > >       drm_dev_put(drm);
> > >
> > > @@ -313,6 +314,7 @@ static void exynos_drm_unbind(struct device *dev)
> > >       drm_dev_unregister(drm);
> > >
> > >       drm_kms_helper_poll_fini(drm);
> > > +     drm_atomic_helper_shutdown(drm);
> > >
> > >       component_unbind_all(drm->dev, drm);
> > >       drm_mode_config_cleanup(drm);
> > > @@ -350,9 +352,18 @@ static int exynos_drm_platform_remove(struct platform_device *pdev)
> > >       return 0;
> > >   }
> > >
> > > +static void exynos_drm_platform_shutdown(struct platform_device *pdev)
> > > +{
> > > +     struct drm_device *drm = platform_get_drvdata(pdev);
> > > +
> > > +     if (drm)
> > > +             drm_atomic_helper_shutdown(drm);
> > > +}
> > > +
> > >   static struct platform_driver exynos_drm_platform_driver = {
> > >       .probe  = exynos_drm_platform_probe,
> > >       .remove = exynos_drm_platform_remove,
> > > +     .shutdown = exynos_drm_platform_shutdown,
> > >       .driver = {
> > >               .name   = "exynos-drm",
> > >               .pm     = &exynos_drm_pm_ops,
> >
> > Best regards
> > --
> > Marek Szyprowski, PhD
> > Samsung R&D Institute Poland
> >