Hi
Am 22.12.24 um 06:00 schrieb Dmitry Baryshkov:
As pointed out by Simona, the drm_atomic_helper_check_modeset() and
drm_atomic_helper_check() require the former function is rerun if the
driver's callbacks modify crtc_state->mode_changed. MSM is one of the
drivers which failed to follow this requirement.
I'm concerned about the implications of this series. How does a driver
upgrade from simple pageflip to full modeset if necessary? The solution
in msm appears to be to run the related test before
drm_atomic_helper_check(). (Right?)
My corner case is in mgag200, which has to reprogram the PLL if the
color mode changes. So it sets mode_changed to true in the primary
plane's atomic_check. [1] This works in practice because the plane
checks run before the CRTC checks. So the CRTC code will do the correct
thing. Reprogramming the PLL means to disable the display at some point.
So it comes down to a full modeset.
You mention that drm_atomic_helper_check() needs to rerun if
mode_changed flips. Would it be possible to implement this instead
within the helper?
Best regards
Thomas
[1]
https://elixir.bootlin.com/linux/v6.12/source/drivers/gpu/drm/mgag200/mgag200_mode.c#L493
As suggested by Simona, implement generic code to verify that the
drivers abide to those requirement and rework MSM driver to follow that
restrictions.
There are no dependencies between core and MSM parts, so they can go
separately via corresponding trees.
Reported-by: Simona Vetter <simona.vetter@xxxxxxxx>
Link: https://lore.kernel.org/dri-devel/ZtW_S0j5AEr4g0QW@phenom.ffwll.local/
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
---
Dmitry Baryshkov (6):
drm/atomic-helper: document drm_atomic_helper_check() restrictions
drm/atomic: prepare to check that drivers follow restrictions for needs_modeset
drm/msm/dpu: don't use active in atomic_check()
drm/msm/dpu: move needs_cdm setting to dpu_encoder_get_topology()
drm/msm/dpu: simplify dpu_encoder_get_topology() interface
drm/msm/dpu: don't set crtc_state->mode_changed from atomic_check()
drivers/gpu/drm/drm_atomic.c | 3 +
drivers/gpu/drm/drm_atomic_helper.c | 86 ++++++++++++++++++++++++++---
drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 4 --
drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 82 +++++++++++++++++----------
drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h | 4 ++
drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c | 26 +++++++++
drivers/gpu/drm/msm/msm_atomic.c | 13 ++++-
drivers/gpu/drm/msm/msm_kms.h | 7 +++
include/drm/drm_atomic.h | 10 ++++
9 files changed, 192 insertions(+), 43 deletions(-)
---
base-commit: b72747fdde637ebf52e181671bf6f41cd773b3e1
change-id: 20241222-drm-dirty-modeset-88079bd27ae6
Best regards,
--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)
