Commit 9c288305 authored by Lauri Tirkkonen's avatar Lauri Tirkkonen Committed by Alex Deucher
Browse files

drm/amd/display: fix initial backlight brightness calculation 



DIV_ROUND_CLOSEST(x, 100) returns either 0 or 1 if 0<x<=100, so the
division needs to be performed after the multiplication and not the
other way around, to properly scale the value.

Fixes: 8b5f3a22 ("drm/amd/display: Fix default DC and AC levels")
Signed-off-by: default avatarLauri Tirkkonen <lauri@hacktheplanet.fi>
Cc: stable@vger.kernel.org
Reviewed-by: default avatarMario Limonciello <mario.limonciello@amd.com>
Link: https://lore.kernel.org/r/aH2Q_HJvxKbW74vU@hacktheplanet.fi


Signed-off-by: default avatarMario Limonciello <mario.limonciello@amd.com>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
parent 1f02f204

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

+2 −2
Original line number Diff line number Diff line
@@ -4983,9 +4983,9 @@ amdgpu_dm_register_backlight_device(struct amdgpu_dm_connector *aconnector) 
	caps = &dm->backlight_caps[aconnector->bl_idx];

	if (get_brightness_range(caps, &min, &max)) {

		if (power_supply_is_system_supplied() > 0)

			props.brightness = (max - min) * DIV_ROUND_CLOSEST(caps->ac_level, 100);

			props.brightness = DIV_ROUND_CLOSEST((max - min) * caps->ac_level, 100);

		else

			props.brightness = (max - min) * DIV_ROUND_CLOSEST(caps->dc_level, 100);

			props.brightness = DIV_ROUND_CLOSEST((max - min) * caps->dc_level, 100);

		/* min is zero, so max needs to be adjusted */

		props.max_brightness = max - min;

		drm_dbg(drm, "Backlight caps: min: %d, max: %d, ac %d, dc %d\n", min, max,