linux-toradex.git/include/drm/drm_vblank_helper.h, branch v7.3-rc2

drm: Rename struct drm_atomic_state to drm_atomic_commit

2026-05-04T04:05:04+00:00

The KMS framework uses two slightly different definitions for the state
concept. For a given object (plane, CRTC, encoder, etc., so
drm_$OBJECT_state), the state is the entire state of that object.
However, at the device level, drm_atomic_state refers to a state update
for a limited number of objects.

Thus, drm_atomic_state isn't the entire device state, but only the full
state of some objects in that device. This has been an endless source of
confusion and thus bugs.

We can rename the drm_atomic_state structure to drm_atomic_commit to
make it less confusing.

This patch was created using:

rg -l drm_atomic_state | \
	xargs sed -i 's/drm_atomic_state/drm_atomic_commit/g; s/drm_atomic_commit_helper/drm_atomic_state_helper/g'
mv drivers/gpu/drm/tests/drm_atomic_state_test.c drivers/gpu/drm/tests/drm_atomic_commit_test.c

Acked-by: Simona Vetter 
Acked-by: Thomas Zimmermann 
Acked-by: Jani Nikula 
Reviewed-by: Luca Ceresoli 
Tested-by: Luca Ceresoli 
Signed-off-by: Maxime Ripard 
Signed-off-by: Dave Airlie 
Link: https://patch.msgid.link/20260427-drm-drm-atomic-update-v4-1-c0e713bfdf25@kernel.org

drm/vblank: Add CRTC helpers for simple use cases

2025-10-01T06:32:00+00:00

Implement atomic_flush, atomic_enable and atomic_disable of struct
drm_crtc_helper_funcs for vblank handling. Driver with no further
requirements can use these functions instead of adding their own.
Also simplifies the use of vblank timers.

The code has been adopted from vkms, which added the funtionality
in commit 3a0709928b17 ("drm/vkms: Add vblank events simulated by
hrtimers").

v3:
- mention vkms (Javier)
v2:
- fix docs

Signed-off-by: Thomas Zimmermann 
Reviewed-by: Javier Martinez Canillas 
Tested-by: Michael Kelley 
Link: https://lore.kernel.org/r/20250916083816.30275-3-tzimmermann@suse.de

drm/vblank: Add vblank timer

2025-10-01T06:31:59+00:00

The vblank timer simulates a vblank interrupt for hardware without
support. Rate-limits the display update frequency.

DRM drivers for hardware without vblank support apply display updates
ASAP. A vblank event informs DRM clients of the completed update.
Userspace compositors immediately schedule the next update, which
creates significant load on virtualization outputs. Display updates
are usually fast on virtualization outputs, as their framebuffers are
in regular system memory and there's no hardware vblank interrupt to
throttle the update rate.

The vblank timer is a HR timer that signals the vblank in software.
It limits the update frequency of a DRM driver similar to a hardware
vblank interrupt. The timer is not synchronized to the actual vblank
interval of the display.

The code has been adopted from vkms, which added the funtionality
in commit 3a0709928b17 ("drm/vkms: Add vblank events simulated by
hrtimers").

The new implementation is part of the existing vblank support,
which sets up the timer automatically. Drivers only have to start
and cancel the vblank timer as part of enabling and disabling the
CRTC. The new vblank helper library provides callbacks for struct
drm_crtc_funcs.

The standard way for handling vblank is to call drm_crtc_handle_vblank().
Drivers that require additional processing, such as vkms, can init
handle_vblank_timeout in struct drm_crtc_helper_funcs to refer to
their timeout handler.

There's a possible deadlock between drm_crtc_handle_vblank() and
hrtimer_cancel(). [1] The implementation avoids to call hrtimer_cancel()
directly and instead signals to the timer function to not restart
itself.

v4:
- fix possible race condition between timeout and atomic commit (Michael)
v3:
- avoid deadlock when cancelling timer (Ville, Lyude)
v2:
- implement vblank timer entirely in vblank helpers
- downgrade overrun warning to debug
- fix docs

Signed-off-by: Thomas Zimmermann 
Tested-by: Louis Chauvet 
Reviewed-by: Louis Chauvet 
Reviewed-by: Javier Martinez Canillas 
Tested-by: Michael Kelley 
Link: https://lore.kernel.org/all/20250510094757.4174662-1-zengheng4@huawei.com/ # [1]
Link: https://lore.kernel.org/r/20250916083816.30275-2-tzimmermann@suse.de