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: 8b5f3a2 ("drm/amd/display: Fix default DC and AC levels")
Signed-off-by: Lauri Tirkkonen <[email protected]>
Cc: [email protected]
Reviewed-by: Mario Limonciello <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Mario Limonciello <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>

Author: lotheac

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

@@ -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,