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[PATCH 4.18 129/197] drm/amd/display: Read back max backlight value at boot




4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: David Francis <David.Francis@xxxxxxx>

[ Upstream commit 53a53f8687faf492df2644d8c18ff0217fc18730 ]

[Why]
If there is no program explicitly setting the backlight
brightness (for example, during a minimal install of linux), the
hardware defaults to maximum brightness but the backlight_device
defaults to 0 value.  Thus, settings displays the wrong brightness
value.

[How]
When creating the backlight device, set brightness to max

Signed-off-by: David Francis <David.Francis@xxxxxxx>
Reviewed-by: Harry Wentland <Harry.Wentland@xxxxxxx>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@xxxxxxx>
Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -1334,6 +1334,7 @@ amdgpu_dm_register_backlight_device(stru
 	struct backlight_properties props = { 0 };
 
 	props.max_brightness = AMDGPU_MAX_BL_LEVEL;
+	props.brightness = AMDGPU_MAX_BL_LEVEL;
 	props.type = BACKLIGHT_RAW;
 
 	snprintf(bl_name, sizeof(bl_name), "amdgpu_bl%d",