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

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Date:   Tue, 6 Sep 2022 22:06:55 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     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, 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 :-)
-Daniel

> ---
>  drivers/gpu/drm/udl/udl_modeset.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/udl/udl_modeset.c b/drivers/gpu/drm/udl/udl_modeset.c
> index 169110d8fc2e..df987644fb5d 100644
> --- a/drivers/gpu/drm/udl/udl_modeset.c
> +++ b/drivers/gpu/drm/udl/udl_modeset.c
> @@ -8,6 +8,7 @@
>   * Copyright (C) 2009 Bernie Thompson <bernie@...gable.com>
>   */
>  
> +#include <drm/drm_atomic.h>
>  #include <drm/drm_atomic_helper.h>
>  #include <drm/drm_crtc_helper.h>
>  #include <drm/drm_damage_helper.h>
> @@ -382,7 +383,7 @@ 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)
> +	if (!drm_atomic_crtc_needs_modeset(crtc_state))
>  		return;
>  
>  	/* enable display */
> -- 
> 2.35.3
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch