linux-kernel - Re: [RFT PATCH 3/6] drm/vc4: Call drm_atomic_helper

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Date:   Thu, 21 Sep 2023 11:46:40 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     dri-devel@...ts.freedesktop.org, Maxime Ripard <mripard@...nel.org>
Cc:     airlied@...il.com, daniel@...ll.ch, emma@...olt.net,
        linux-kernel@...r.kernel.org
Subject: Re: [RFT PATCH 3/6] drm/vc4: Call drm_atomic_helper_shutdown() at
 shutdown time

Hi,

On Fri, Sep 1, 2023 at 4:40 PM Douglas Anderson <dianders@...omium.org> wrote:
>
> Based on grepping through the source code these drivers appear 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.
>
> Suggested-by: Maxime Ripard <mripard@...nel.org>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
> This commit is only compile-time tested.
>
> Though this patch could be squashed into the patch ("drm: Call
> drm_atomic_helper_shutdown() at shutdown time for misc drivers"), I
> kept it separate to call attention to this driver. While writing this
> patch, I noticed that the bind() function 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
>
>  drivers/gpu/drm/vc4/vc4_drv.c | 36 ++++++++++++++++++++++-------------
>  1 file changed, 23 insertions(+), 13 deletions(-)

Landed to drm-misc-next:

013d382d11a2 drm/vc4: Call drm_atomic_helper_shutdown() at shutdown time