[PATCH 2/5] drm/amd/display: Don't force a modeset when the ABM level changes

[Hugo Sales <hugo@hsal.es>]

An upcoming patch commits panel_power_savings writes from the kernel
without a modeset. amdgpu_dm_atomic_check() sets connectors_changed on the
CRTC when the connector's ABM level changes, so that commit would fail
with -EINVAL

The flag came in with commit c5892a102182 ("drm/amd/display: Fix dmesg
warning from setting abm level"), because setting the level did not add
the CRTC to the commit and no stream update reached DC. With other changes
since then, that fix is no longer needed. On the non-modeset path,
dm_update_crtc_state() copies the level from the connector to the CRTC
state and the commit tail sends a changed level as stream_update.abm_level

Keep the flag for scaling changes, which move the stream's source and
destination rectangles

Signed-off-by: Hugo Sales <hugo@hsal.es>
---
Upstream, a level already reaches DC this way when a compositor commits
the connector after a panel_power_savings write. The store has already
written the level into the current connector state, so the old and new
connector states match and atomic check doesn't ask for a modeset. Only
the CRTC state, which still holds the old level, sees the change. With
this series, the hardware tests in the cover letter apply every level this
way

If a level change through the KMS property should still force a modeset,
the store could flag its own commits instead. It would set a flag in
dm_connector_state that atomic check reads to skip connectors_changed.
duplicate_state wouldn't copy the flag, so it only lasts for that one
commit. I think it's simpler to treat the change the same way whoever made
it, but I can send that version

Scaling has been in the same check since commit 3c6d1aeb4342.
From my reading the non-modeset path handles it too, as a src/dst stream
update, but it changes the scaler ratio and I can't tell whether DC needs
the full validation for that. Could it go as well?
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

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 dfbc384fbbdb4..256699cdd0b5c 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -6304,8 +6304,7 @@ STATIC_IFN_KUNIT int amdgpu_dm_atomic_check(struct drm_device *dev,
 			goto fail;
 		}
 
-		if (dm_old_con_state->abm_level != dm_new_con_state->abm_level ||
-		    dm_old_con_state->scaling != dm_new_con_state->scaling)
+		if (dm_old_con_state->scaling != dm_new_con_state->scaling)
 			new_crtc_state->connectors_changed = true;
 	}
 

-- 
2.56.0