linux-kernel - Re: [PATCH 01/12] drm/udl: Restore display mode on resume

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Message-ID: <87sfl3enqu.wl-tiwai@suse.de>
Date:   Wed, 07 Sep 2022 07:51:05 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Daniel Vetter <daniel@...ll.ch>
Cc:     Takashi Iwai <tiwai@...e.de>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 01/12] drm/udl: Restore display mode on resume

On Tue, 06 Sep 2022 22:06:55 +0200,
Daniel Vetter wrote:
> 
> On Tue, Aug 16, 2022 at 05:36:44PM +0200, Takashi Iwai wrote:
> > From: Thomas Zimmermann <tzimmermann@...e.de>
> > 
> > Restore the display mode whne resuming from suspend. Currently, the
> > display remains dark.
> > 
> > On resume, the CRTC's mode does not change, but the 'active' flag
> > changes to 'true'. Taking this into account when considering a mode
> > switch restores the display mode.
> > 
> > The bug is reproducable by using Gnome with udl and observing the
> > adapter's suspend/resume behavior.
> > 
> > Signed-off-by: Thomas Zimmermann <tzimmermann@...e.de>
> > Signed-off-by: Takashi Iwai <tiwai@...e.de>
> 
> This patch isn't great and incomplete, see
> 
> https://lore.kernel.org/dri-devel/YxegiQFAv+OWjjqE@phenom.ffwll.local/
> 
> You need cc: stable and fixes: 997d33c35618 and actually just remove the
> entire check :-)

OK, then is something like below?

I already submitted v2 yesterday (as I overlooked your reply), so I'll
respin v3 with this (and your ack) if that's OK.


thanks,

Takashi

-- 8< --
From: Takashi Iwai <tiwai@...e.de>
Subject: [PATCH] drm/udl: Restore display mode on resume

Restore the display mode whne resuming from suspend. Currently, the
display remains dark.

On resume, the CRTC's mode does not change, but the 'active' flag
changes to 'true'. Taking this into account when considering a mode
switch restores the display mode.

The bug is reproducable by using Gnome with udl and observing the
adapter's suspend/resume behavior.

Actually, the whole check added in udl_simple_display_pipe_enable()
about the crtc_state->mode_changed was bogus.  We should drop the
whole check and always apply the mode change in this function.

[ tiwai -- Drop the mode_changed check entirely instead, per Daniel's
  suggestion ]

Fixes: 997d33c35618 ("drm/udl: Inline DPMS code into CRTC enable and disable functions")
Cc: <stable@...r.kernel.org>
Signed-off-by: Thomas Zimmermann <tzimmermann@...e.de>
Suggested-by: Daniel Vetter <daniel.vetter@...ll.ch>
Signed-off-by: Takashi Iwai <tiwai@...e.de>
---
 drivers/gpu/drm/udl/udl_modeset.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/gpu/drm/udl/udl_modeset.c b/drivers/gpu/drm/udl/udl_modeset.c
index 169110d8fc2e..34ce5b43c5db 100644
--- a/drivers/gpu/drm/udl/udl_modeset.c
+++ b/drivers/gpu/drm/udl/udl_modeset.c
@@ -382,9 +382,6 @@ udl_simple_display_pipe_enable(struct drm_simple_display_pipe *pipe,
 
 	udl_handle_damage(fb, &shadow_plane_state->data[0], 0, 0, fb->width, fb->height);
 
-	if (!crtc_state->mode_changed)
-		return;
-
 	/* enable display */
 	udl_crtc_write_mode_to_hw(crtc);
 }
-- 
2.35.3