[PATCH resend v2] drm: renesas: shmobile: Call drm_helper_force_disable_all() at shutdown time

[Doug Anderson]

Hi,

On Wed, May 29, 2024 at 5:16 AM Geert Uytterhoeven
<geert+renesas at glider.be> wrote:
>
> From: Douglas Anderson <dianders at chromium.org>
>
> Based on grepping through the source code, this driver appears to be
> missing a call to drm_atomic_helper_shutdown() at system shutdown time.
> This is important because drm_helper_force_disable_all() will cause
> panels to get disabled cleanly which may be important for their power
> sequencing.  Future changes will remove any custom powering off in
> individual panel drivers so the DRM drivers need to start getting this
> right.
>
> The fact that we should call drm_atomic_helper_shutdown() in the case of
> OS shutdown comes straight out of the kernel doc "driver instance
> overview" in drm_drv.c.
>
> Suggested-by: Maxime Ripard <mripard at kernel.org>
> Signed-off-by: Douglas Anderson <dianders at chromium.org>
> Link: https://lore.kernel.org/r/20230901164111.RFT.15.Iaf638a1d4c8b3c307a6192efabb4cbb06b195f15@changeid
> [geert: s/drm_helper_force_disable_all/drm_atomic_helper_shutdown/]
> [geert: shmob_drm_remove() already calls drm_atomic_helper_shutdown]
> Signed-off-by: Geert Uytterhoeven <geert+renesas at glider.be>
> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> ---
> v2:
>   - Add Reviewed-by.
>
> Tested on Atmark Techno Armadillo-800-EVA.
> ---
>  drivers/gpu/drm/renesas/shmobile/shmob_drm_drv.c | 8 ++++++++
>  1 file changed, 8 insertions(+)

FWIW: I've created a patch to list DRM modeset drivers that handle
shutdown properly [1]. For now "shmob-drm" is not part of that
patchset. Assuming my patch lands we'll have to later add it to the
list.

[1] https://lore.kernel.org/r/20240611074846.1.Ieb287c2c3ee3f6d3b0d5f49b29f746b93621749c@changeid

I will also note that the subject/description of this patch could be
adjusted. They still reference "drm_helper_force_disable_all" which
should have been changed to "drm_atomic_helper_shutdown".

-Doug