[PATCH] drm/atomic-helper: Don't set deadline for modesets

[Daniel Vetter]

If the crtc is being switched on or off then the semantics of
computing the timestampe of the next vblank is somewhat ill-defined.
And indeed, the code splats with a warning in the timestamp
computation code. Specifically it hits the check to make sure that
atomic drivers have full set up the timing constants in the drm_vblank
structure, and that's just not the case before the crtc is actually
on.

For robustness it seems best to just not set deadlines for modesets.

Link: https://lore.kernel.org/dri-devel/dfc21f18-7e1e-48f0-c05a-d659b9c90b91@linaro.org/
Fixes: d39e48ca80c0 ("drm/atomic-helper: Set fence deadline for vblank")
Cc: Rob Clark <robdclark at chromium.org>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Cc: Maxime Ripard <mripard at kernel.org>
Cc: Thomas Zimmermann <tzimmermann at suse.de>
Reported-by: Dmitry Baryshkov <dmitry.baryshkov at linaro.org>
Tested-by: Dmitry Baryshkov <dmitry.baryshkov at linaro.org> # test patch only
Cc: Dmitry Baryshkov <dmitry.baryshkov at linaro.org>
Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
---
 drivers/gpu/drm/drm_atomic_helper.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index f21b5a74176c..6640d80d84f3 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -1528,6 +1528,9 @@ static void set_fence_deadline(struct drm_device *dev,
 	for_each_new_crtc_in_state (state, crtc, new_crtc_state, i) {
 		ktime_t v;
 
+		if (drm_atomic_crtc_needs_modeset(new_crtc_state))
+			continue;
+
 		if (drm_crtc_next_vblank_start(crtc, &v))
 			continue;
 
-- 
2.40.0