drm/amd/display: Allow backlight to go below `AMDGPU_DM_DEFAULT_MIN_BACKLIGHT`

[ Upstream commit 87d749a6aab73d8069d0345afaa98297816cb220 ]

The issue with panel power savings compatibility below
`AMDGPU_DM_DEFAULT_MIN_BACKLIGHT` happens at
`AMDGPU_DM_DEFAULT_MIN_BACKLIGHT` as well.

That issue will be fixed separately, so don't prevent the backlight
brightness from going that low.

Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Thomas Weißschuh <linux@weissschuh.net>
Link: https://lore.kernel.org/amd-gfx/be04226a-a9e3-4a45-a83b-6d263c6557d8@t-8ch.de/T/#m400dee4e2fc61fe9470334d20a7c8c89c9aef44f
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index f964e79babdb54fcb2c944bd39e43167fdde15d9..bfa15d895955309320d8377def844ce612926c6a 100644 (file)
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -3936,7 +3936,7 @@ static void amdgpu_dm_update_backlight_caps(struct amdgpu_display_manager *dm,
                int spread = caps.max_input_signal - caps.min_input_signal;
 
                if (caps.max_input_signal > AMDGPU_DM_DEFAULT_MAX_BACKLIGHT ||
-                   caps.min_input_signal < AMDGPU_DM_DEFAULT_MIN_BACKLIGHT ||
+                   caps.min_input_signal < 0 ||
                    spread > AMDGPU_DM_DEFAULT_MAX_BACKLIGHT ||
                    spread < AMDGPU_DM_MIN_SPREAD) {
                        DRM_DEBUG_KMS("DM: Invalid backlight caps: min=%d, max=%d\n",