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

[Laurent Pinchart]

On Tue, Dec 05, 2023 at 02:31:24PM +0100, Geert Uytterhoeven wrote:
> On Tue, Dec 5, 2023 at 1:16 PM Laurent Pinchart wrote:
> > On Tue, Dec 05, 2023 at 12:30:02PM +0100, Geert Uytterhoeven 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>
> 
> Thanks!
> 
> > > Panel-simple does print two new warnings:
> > >
> > >     +panel-simple panel: Skipping disable of already disabled panel
> > >     +panel-simple panel: Skipping unprepare of already unprepared panel
> >
> > Have you investigated where this comes from ?
> 
> Meh, I knew I forgot something ;-)
> 
> The panel is unprepared and disabled a first time from shmob_drm's
> .shutdown() callback:
> 
>   shmob_drm_shutdown
>     drm_atomic_helper_shutdown
>       drm_atomic_helper_disable_all
>         drm_atomic_commit
>           drm_atomic_helper_commit
>             commit_tail
>               drm_atomic_helper_commit_tail
>                 drm_atomic_helper_commit_modeset_disables
>                   disable_outputs
>                     drm_atomic_bridge_chain_disable
>                         drm_panel_disable
>                     drm_atomic_bridge_chain_post_disable
>                         drm_panel_unprepare
> 
> And a second time from simple_panel's .shutdown() callback():
> 
>   panel_simple_platform_shutdown
>     panel_simple_shutdown
>       drm_panel_disable
>       drm_panel_unprepare

That looks like what Doug mentioned should be removed in the commit
message of this patch (a confirmation would be nice). It should be fine
for now.

-- 
Regards,

Laurent Pinchart