[PATCH] drm/gud: Merge damage clips in full update mode

[PATCH] drm/gud: Merge damage clips in full update mode

[Sophie D]

When running in full update mode, previously small updates (such as
moving the mouse across the screen) would cause many full frames to be
generated. This would bog down the bus and lower the effective framerate
significantly - I was seeing a drop from 60 FPS to 2 FPS.

This patch fixes the bug by merging damage clips together.

Fixes: 73cfd166e045 ("drm/gud: Replace simple display pipe with DRM atomic helpers")
Cc: <stable@vger.kernel.org> # 6.18.x
Signed-off-by: Sophie D <patches@scd31.com>
---
 drivers/gpu/drm/gud/gud_pipe.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/gud/gud_pipe.c b/drivers/gpu/drm/gud/gud_pipe.c
index 5ef887d84..20418bf81 100644
--- a/drivers/gpu/drm/gud/gud_pipe.c
+++ b/drivers/gpu/drm/gud/gud_pipe.c
@@ -647,9 +647,14 @@ void gud_plane_atomic_update(struct drm_plane *plane,
 	if (ret)
 		goto out;
 
-	drm_atomic_helper_damage_iter_init(&iter, old_state, new_state);
-	drm_atomic_for_each_plane_damage(&iter, &damage)
-		gud_fb_handle_damage(gdrm, fb, &shadow_plane_state->data[0], &damage);
+	if (gdrm->flags & GUD_DISPLAY_FLAG_FULL_UPDATE) {
+		if (drm_atomic_helper_damage_merged(old_state, new_state, &damage))
+			gud_fb_handle_damage(gdrm, fb, &shadow_plane_state->data[0], &damage);
+	} else {
+		drm_atomic_helper_damage_iter_init(&iter, old_state, new_state);
+		drm_atomic_for_each_plane_damage(&iter, &damage)
+			gud_fb_handle_damage(gdrm, fb, &shadow_plane_state->data[0], &damage);
+	}
 
 	drm_gem_fb_end_cpu_access(fb, DMA_FROM_DEVICE);
 
-- 
2.55.0

Re: [PATCH] drm/gud: Merge damage clips in full update mode

[Thomas Zimmermann]

Hi

Am 08.09.26 um 01:08 schrieb Sophie D:
> When running in full update mode, previously small updates (such as
> moving the mouse across the screen) would cause many full frames to be
> generated. This would bog down the bus and lower the effective framerate
> significantly - I was seeing a drop from 60 FPS to 2 FPS.
>
> This patch fixes the bug by merging damage clips together.
>
> Fixes: 73cfd166e045 ("drm/gud: Replace simple display pipe with DRM atomic helpers")
> Cc: <stable@vger.kernel.org> # 6.18.x
> Signed-off-by: Sophie D <patches@scd31.com>
> ---
>   drivers/gpu/drm/gud/gud_pipe.c | 11 ++++++++---
>   1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/gud/gud_pipe.c b/drivers/gpu/drm/gud/gud_pipe.c
> index 5ef887d84..20418bf81 100644
> --- a/drivers/gpu/drm/gud/gud_pipe.c
> +++ b/drivers/gpu/drm/gud/gud_pipe.c
> @@ -647,9 +647,14 @@ void gud_plane_atomic_update(struct drm_plane *plane,
>   	if (ret)
>   		goto out;
>   
> -	drm_atomic_helper_damage_iter_init(&iter, old_state, new_state);
> -	drm_atomic_for_each_plane_damage(&iter, &damage)
> -		gud_fb_handle_damage(gdrm, fb, &shadow_plane_state->data[0], &damage);
> +	if (gdrm->flags & GUD_DISPLAY_FLAG_FULL_UPDATE) {
> +		if (drm_atomic_helper_damage_merged(old_state, new_state, &damage))
> +			gud_fb_handle_damage(gdrm, fb, &shadow_plane_state->data[0], &damage);
> +	} else {
> +		drm_atomic_helper_damage_iter_init(&iter, old_state, new_state);
> +		drm_atomic_for_each_plane_damage(&iter, &damage)
> +			gud_fb_handle_damage(gdrm, fb, &shadow_plane_state->data[0], &damage);
> +	}

Such state needs to be checked much earlier. Please set 
plane_state->ignore_damage_clips [1] at the end of 
gud_plane_atomic_check [2] if in full-update mode.  The damage iterator 
will then do the right thing.

[1] 
https://elixir.bootlin.com/linux/v7.2.2/source/include/drm/drm_plane.h#L207
[2] 
https://elixir.bootlin.com/linux/v7.2.2/source/drivers/gpu/drm/gud/gud_pipe.c#L569

Best regards
Thomas

>   
>   	drm_gem_fb_end_cpu_access(fb, DMA_FROM_DEVICE);
>   

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, (HRB 36809, AG Nürnberg)

[PATCH v2] drm/gud: Ignore damage clips in full update mode

[Sophie D]

When running in full update mode, previously small updates (such as
moving the mouse across the screen) would cause many full frames to be
generated. This would bog down the bus and lower the effective framerate
significantly - I was seeing a drop from 60 FPS to 2 FPS.

Set ignore_damage_clips in full update mode so the damage iterator
yields a single full-plane rectangle instead of one per clip.

Fixes: 73cfd166e045 ("drm/gud: Replace simple display pipe with DRM atomic helpers")
Cc: <stable@vger.kernel.org> # 6.18.x
Signed-off-by: Sophie D <patches@scd31.com>
---
v2: set ignore_damage_clips in atomic_check instead of merging clips in
    atomic_update (Thomas Zimmermann)

 drivers/gpu/drm/gud/gud_pipe.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/gud/gud_pipe.c b/drivers/gpu/drm/gud/gud_pipe.c
index 5ef887d84..3388fdc8e 100644
--- a/drivers/gpu/drm/gud/gud_pipe.c
+++ b/drivers/gpu/drm/gud/gud_pipe.c
@@ -482,6 +482,9 @@ int gud_plane_atomic_check(struct drm_plane *plane,
 	if (!new_plane_state->visible)
 		return 0;
 
+	if (gdrm->flags & GUD_DISPLAY_FLAG_FULL_UPDATE)
+		new_plane_state->ignore_damage_clips = true;
+
 	if (old_plane_state->rotation != new_plane_state->rotation)
 		crtc_state->mode_changed = true;
 
-- 
2.55.0

Re: [PATCH v2] drm/gud: Ignore damage clips in full update mode

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] The iterator variable `connector_state` leaks out of `for_each_new_connector_in_state`, bypassing the fallback search.
--

commit 4deed33a0bafa9e2ff82e53d1da0f3130451d673
Author: Sophie D <patches@scd31.com>

drm/gud: Ignore damage clips in full update mode

When running in full update mode, previously small updates (such as
moving the mouse across the screen) would cause many full frames to be
generated. This would bog down the bus and lower the effective framerate
significantly - I was seeing a drop from 60 FPS to 2 FPS.

> diff --git a/drivers/gpu/drm/gud/gud_pipe.c b/drivers/gpu/drm/gud/gud_pipe.c
> index 5ef887d8485a3..3388fdc8ea7b5 100644
> --- a/drivers/gpu/drm/gud/gud_pipe.c
> +++ b/drivers/gpu/drm/gud/gud_pipe.c
> @@ -482,6 +482,9 @@ int gud_plane_atomic_check(struct drm_plane *plane,
>  	if (!new_plane_state->visible)
>  		return 0;
>  
> +	if (gdrm->flags & GUD_DISPLAY_FLAG_FULL_UPDATE)
> +		new_plane_state->ignore_damage_clips = true;
> +
>  	if (old_plane_state->rotation != new_plane_state->rotation)
>  		crtc_state->mode_changed = true;
>  

[Severity: High]
This isn't a bug introduced by this patch, but while reviewing
gud_plane_atomic_check(), I noticed an issue with the fallback search for
the connector.

Does connector_state bypass the fallback search here?

	for_each_new_connector_in_state(state, connector, connector_state, i) {
		if (connector_state->crtc)
			break;
	}

	/*
	 * DRM_IOCTL_MODE_OBJ_SETPROPERTY on the rotation property will not have
	 * the connector included in the state.
	 */
	if (!connector_state) {
		struct drm_connector_list_iter conn_iter;

If the loop finishes without finding a matching CRTC, connector_state retains
the pointer to the last evaluated connector rather than evaluating to NULL.
This happens because short-circuit evaluation prevents the macro's assignment
block from running on the final iteration.

Could this cause the driver to extract properties and the connector index from
an unrelated or disconnected connector and send them to the hardware device
during the atomic check phase, leading to hardware misconfiguration?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260910014910.8564-1-patches@scd31.com?part=1

Re: [PATCH] drm/gud: Merge damage clips in full update mode

[Sophie D]

Hello,

>
> Such state needs to be checked much earlier. Please set 
> plane_state->ignore_damage_clips [1] at the end of 
> gud_plane_atomic_check [2] if in full-update mode.  The damage iterator 
> will then do the right thing.

Thank you for reviewing! I've made this change and have tested it on my
hardware.

Sophie

Re: [PATCH v2] drm/gud: Ignore damage clips in full update mode

[Thomas Zimmermann]

Am 10.09.26 um 03:49 schrieb Sophie D:
> When running in full update mode, previously small updates (such as
> moving the mouse across the screen) would cause many full frames to be
> generated. This would bog down the bus and lower the effective framerate
> significantly - I was seeing a drop from 60 FPS to 2 FPS.
>
> Set ignore_damage_clips in full update mode so the damage iterator
> yields a single full-plane rectangle instead of one per clip.
>
> Fixes: 73cfd166e045 ("drm/gud: Replace simple display pipe with DRM atomic helpers")
> Cc: <stable@vger.kernel.org> # 6.18.x
> Signed-off-by: Sophie D <patches@scd31.com>

Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>

Thanks for the fix.

> ---
> v2: set ignore_damage_clips in atomic_check instead of merging clips in
>      atomic_update (Thomas Zimmermann)
>
>   drivers/gpu/drm/gud/gud_pipe.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/drivers/gpu/drm/gud/gud_pipe.c b/drivers/gpu/drm/gud/gud_pipe.c
> index 5ef887d84..3388fdc8e 100644
> --- a/drivers/gpu/drm/gud/gud_pipe.c
> +++ b/drivers/gpu/drm/gud/gud_pipe.c
> @@ -482,6 +482,9 @@ int gud_plane_atomic_check(struct drm_plane *plane,
>   	if (!new_plane_state->visible)
>   		return 0;
>   
> +	if (gdrm->flags & GUD_DISPLAY_FLAG_FULL_UPDATE)
> +		new_plane_state->ignore_damage_clips = true;
> +
>   	if (old_plane_state->rotation != new_plane_state->rotation)
>   		crtc_state->mode_changed = true;
>   

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, (HRB 36809, AG Nürnberg)

Re: [PATCH v2] drm/gud: Ignore damage clips in full update mode

[Ruben Wauters]

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On Thu, 2026-09-10 at 08:17 +0200, Thomas Zimmermann wrote:
> 
> Am 10.09.26 um 03:49 schrieb Sophie D:
> > When running in full update mode, previously small updates (such as
> > moving the mouse across the screen) would cause many full frames to be
> > generated. This would bog down the bus and lower the effective framerate
> > significantly - I was seeing a drop from 60 FPS to 2 FPS.
> > 
> > Set ignore_damage_clips in full update mode so the damage iterator
> > yields a single full-plane rectangle instead of one per clip.
> > 
> > Fixes: 73cfd166e045 ("drm/gud: Replace simple display pipe with DRM atomic helpers")
> > Cc: <stable@vger.kernel.org> # 6.18.x
> > Signed-off-by: Sophie D <patches@scd31.com>
> 
> Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Ruben Wauters <rubenru09@aol.com>
> 
> Thanks for the fix.
> 
> > ---
> > v2: set ignore_damage_clips in atomic_check instead of merging clips in
> >      atomic_update (Thomas Zimmermann)
> > 
> >   drivers/gpu/drm/gud/gud_pipe.c | 3 +++
> >   1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/gud/gud_pipe.c b/drivers/gpu/drm/gud/gud_pipe.c
> > index 5ef887d84..3388fdc8e 100644
> > --- a/drivers/gpu/drm/gud/gud_pipe.c
> > +++ b/drivers/gpu/drm/gud/gud_pipe.c
> > @@ -482,6 +482,9 @@ int gud_plane_atomic_check(struct drm_plane *plane,
> >   	if (!new_plane_state->visible)
> >   		return 0;
> >   
> > +	if (gdrm->flags & GUD_DISPLAY_FLAG_FULL_UPDATE)
> > +		new_plane_state->ignore_damage_clips = true;
> > +
> >   	if (old_plane_state->rotation != new_plane_state->rotation)
> >   		crtc_state->mode_changed = true;
> >   

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