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drm/amd/display: fix initial backlight brightness calculation

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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: 8b5f3a229a ("drm/amd/display: Fix default DC and AC levels")
Signed-off-by: Lauri Tirkkonen <lauri@hacktheplanet.fi>
Cc: stable@vger.kernel.org
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Link: https://lore.kernel.org/r/aH2Q_HJvxKbW74vU@hacktheplanet.fi
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
This commit is contained in:
Lauri Tirkkonen
2025-07-21 09:59:40 +09:00
committed by Alex Deucher
parent 1f02f2044b
commit 9c2883057b
1 changed files with 2 additions and 2 deletions
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4
drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
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@@ -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,