Commit 318b1c36 authored by Vivek Das Mohapatra's avatar Vivek Das Mohapatra Committed by Alex Deucher
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drm/amd/display: Initialise backlight level values from hw 



Internal backlight levels are initialised from ACPI but the values
are sometimes out of sync with the levels in effect until there has
been a read from hardware (eg triggered by reading from sysfs).

This means that the first drm_commit can cause the levels to be set
to a different value than the actual starting one, which results in
a sudden change in brightness.

This path shows the problem (when the values are out of sync):

   amdgpu_dm_atomic_commit_tail()
   -> amdgpu_dm_commit_streams()
   -> amdgpu_dm_backlight_set_level(..., dm->brightness[n])

This patch calls the backlight ops get_brightness explicitly
at the end of backlight registration to make sure dm->brightness[n]
is in sync with the actual hardware levels.

Fixes: 2fe87f54 ("drm/amd/display: Set default brightness according to ACPI")
Signed-off-by: default avatarVivek Das Mohapatra <vivek@collabora.com>
Reviewed-by: default avatarMario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
parent fff90bb3

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

+17 −1
Original line number Diff line number Diff line
@@ -5279,6 +5279,8 @@ amdgpu_dm_register_backlight_device(struct amdgpu_dm_connector *aconnector) 
	struct amdgpu_dm_backlight_caps *caps;

	char bl_name[16];

	int min, max;

	int real_brightness;

	int init_brightness;



	if (aconnector->bl_idx == -1)

		return;
@@ -5303,6 +5305,8 @@ amdgpu_dm_register_backlight_device(struct amdgpu_dm_connector *aconnector) 
	} else

		props.brightness = props.max_brightness = MAX_BACKLIGHT_LEVEL;



	init_brightness = props.brightness;



	if (caps->data_points && !(amdgpu_dc_debug_mask & DC_DISABLE_CUSTOM_BRIGHTNESS_CURVE)) {

		drm_info(drm, "Using custom brightness curve\n");

		props.scale = BACKLIGHT_SCALE_NON_LINEAR;
@@ -5321,9 +5325,21 @@ amdgpu_dm_register_backlight_device(struct amdgpu_dm_connector *aconnector) 
	if (IS_ERR(dm->backlight_dev[aconnector->bl_idx])) {

		drm_err(drm, "DM: Backlight registration failed!\n");

		dm->backlight_dev[aconnector->bl_idx] = NULL;

	} else

	} else {

		/*

		 * dm->brightness[x] can be inconsistent just after startup until

		 * ops.get_brightness is called.

		 */

		real_brightness =

			amdgpu_dm_backlight_ops.get_brightness(dm->backlight_dev[aconnector->bl_idx]);



		if (real_brightness != init_brightness) {

			dm->actual_brightness[aconnector->bl_idx] = real_brightness;

			dm->brightness[aconnector->bl_idx] = real_brightness;

		}

		drm_dbg_driver(drm, "DM: Registered Backlight device: %s\n", bl_name);

	}

}



static int initialize_plane(struct amdgpu_display_manager *dm,

			    struct amdgpu_mode_info *mode_info, int plane_id,