[PATCH 5.17 303/343] amd/display: set backlight only if required

[Greg Kroah-Hartman]

From: Shirish S <shirish.s@xxxxxxx>

commit 4052287a75eb3fc0f487fcc5f768a38bede455c8 upstream.

[Why]
comparing pwm bl values (coverted) with user brightness(converted)
levels in commit_tail leads to continuous setting of backlight via dmub
as they don't to match.
This leads overdrive in queuing of commands to DMCU that sometimes lead
to depending on load on DMCU fw:

"[drm:dc_dmub_srv_wait_idle] *ERROR* Error waiting for DMUB idle: status=3"

[How]
Store last successfully set backlight value and compare with it instead
of pwm reads which is not what we should compare with.

Signed-off-by: Shirish S <shirish.s@xxxxxxx>
Reviewed-by: Harry Wentland <harry.wentland@xxxxxxx>
Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |    7 ++++---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h |    6 ++++++
 2 files changed, 10 insertions(+), 3 deletions(-)

--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -3951,7 +3951,7 @@ static u32 convert_brightness_to_user(co
 				 max - min);
 }
 
-static int amdgpu_dm_backlight_set_level(struct amdgpu_display_manager *dm,
+static void amdgpu_dm_backlight_set_level(struct amdgpu_display_manager *dm,
 					 int bl_idx,
 					 u32 user_brightness)
 {
@@ -3982,7 +3982,8 @@ static int amdgpu_dm_backlight_set_level
 			DRM_DEBUG("DM: Failed to update backlight on eDP[%d]\n", bl_idx);
 	}
 
-	return rc ? 0 : 1;
+	if (rc)
+		dm->actual_brightness[bl_idx] = user_brightness;
 }
 
 static int amdgpu_dm_backlight_update_status(struct backlight_device *bd)
@@ -9914,7 +9915,7 @@ static void amdgpu_dm_atomic_commit_tail
 	/* restore the backlight level */
 	for (i = 0; i < dm->num_of_edps; i++) {
 		if (dm->backlight_dev[i] &&
-		    (amdgpu_dm_backlight_get_level(dm, i) != dm->brightness[i]))
+		    (dm->actual_brightness[i] != dm->brightness[i]))
 			amdgpu_dm_backlight_set_level(dm, i, dm->brightness[i]);
 	}
 #endif
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
@@ -540,6 +540,12 @@ struct amdgpu_display_manager {
 	 * cached backlight values.
 	 */
 	u32 brightness[AMDGPU_DM_MAX_NUM_EDP];
+	/**
+	 * @actual_brightness:
+	 *
+	 * last successfully applied backlight values.
+	 */
+	u32 actual_brightness[AMDGPU_DM_MAX_NUM_EDP];
 };
 
 enum dsc_clock_force_state {