[PATCH] drm/amd/display: Always get CRTC updated constant values inside commit tail

[Rodrigo Siqueira]

We recently improved our display atomic commit and tail sequence to
avoid some issues related to concurrency. One of the major changes
consisted of moving the interrupt disable and the stream release from
our atomic commit to our atomic tail (commit 6d90a208cfff
("drm/amd/display: Move disable interrupt into commit tail")) .
However, the new code introduced inside our commit tail function was
inserted right after the function
drm_atomic_helper_update_legacy_modeset_state(), which has routines for
updating internal data structs related to timestamps. As a result, in
certain conditions, the display module can reach a situation where we
update our constants and, after that, clean it. This situation generates
the following warning:

 amdgpu 0000:03:00.0: drm_WARN_ON_ONCE(drm_drv_uses_atomic_modeset(dev))
 WARNING: CPU: 6 PID: 1269 at drivers/gpu/drm/drm_vblank.c:722
 drm_crtc_vblank_helper_get_vblank_timestamp_internal+0x32b/0x340 [drm]
 ...
 RIP:
 0010:drm_crtc_vblank_helper_get_vblank_timestamp_internal+0x32b/0x340
 [drm]
 ...
 Call Trace:
  ? dc_stream_get_vblank_counter+0x57/0x60 [amdgpu]
  drm_crtc_vblank_helper_get_vblank_timestamp+0x1c/0x20 [drm]
  drm_get_last_vbltimestamp+0xad/0xc0 [drm]
  drm_reset_vblank_timestamp+0x63/0xd0 [drm]
  drm_crtc_vblank_on+0x85/0x150 [drm]
  amdgpu_dm_atomic_commit_tail+0xaf1/0x2330 [amdgpu]
  commit_tail+0x99/0x130 [drm_kms_helper]
  drm_atomic_helper_commit+0x123/0x150 [drm_kms_helper]
  amdgpu_dm_atomic_commit+0x11/0x20 [amdgpu]
  drm_atomic_commit+0x4a/0x50 [drm]
  drm_atomic_helper_set_config+0x7c/0xc0 [drm_kms_helper]
  drm_mode_setcrtc+0x20b/0x7e0 [drm]
  ? tomoyo_path_number_perm+0x6f/0x200
  ? drm_mode_getcrtc+0x190/0x190 [drm]
  drm_ioctl_kernel+0xae/0xf0 [drm]
  drm_ioctl+0x245/0x400 [drm]
  ? drm_mode_getcrtc+0x190/0x190 [drm]
  amdgpu_drm_ioctl+0x4e/0x80 [amdgpu]
  __x64_sys_ioctl+0x91/0xc0
  do_syscall_64+0x38/0x90
  entry_SYSCALL_64_after_hwframe+0x44/0xa9
 ...

For fixing this issue we rely upon a refactor introduced on
drm_atomic_helper_update_legacy_modeset_state ("Remove the timestamping
constant update from drm_atomic_helper_update_legacy_modeset_state()")
which decouples constant values update from
drm_atomic_helper_update_legacy_modeset_state to a new helper.
Basically, this commit uses this new helper and place it right after our
release module to avoid a situation where our CRTC struct gets wrong
values.

Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira at amd.com>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 1772adcf9f98..91f7fdeee758 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -8121,7 +8121,6 @@ static void amdgpu_dm_atomic_commit_tail(struct drm_atomic_state *state)
 	trace_amdgpu_dm_atomic_commit_tail_begin(state);
 
 	drm_atomic_helper_update_legacy_modeset_state(dev, state);
-	drm_atomic_helper_calc_timestamping_constants(state);
 
 	dm_state = dm_atomic_get_new_state(state);
 	if (dm_state && dm_state->context) {
@@ -8148,6 +8147,8 @@ static void amdgpu_dm_atomic_commit_tail(struct drm_atomic_state *state)
 		}
 	}
 
+	drm_atomic_helper_calc_timestamping_constants(state);
+
 	/* update changed items */
 	for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state, new_crtc_state, i) {
 		struct amdgpu_crtc *acrtc = to_amdgpu_crtc(crtc);
-- 
2.29.2