From: Mario Limonciello <mario.limonciello@xxxxxxx> commit 327e62f47eb57ae5ff63de82b0815557104e439a upstream. Currently amdgpu takes backlight caps provided by the ACPI tables on systems as is. If the firmware sets maximums that are too low this means that users don't get a good experience. To avoid having to maintain a quirk list of such systems, do a sanity check on the values. Check that the spread is at least half of the values that amdgpu would use if no ACPI table was found and if not use the amdgpu defaults. Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3020 Reviewed-by: Harry Wentland <harry.wentland@xxxxxxx> Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx> Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c @@ -3906,6 +3906,7 @@ static int amdgpu_dm_mode_config_init(st #define AMDGPU_DM_DEFAULT_MIN_BACKLIGHT 12 #define AMDGPU_DM_DEFAULT_MAX_BACKLIGHT 255 +#define AMDGPU_DM_MIN_SPREAD ((AMDGPU_DM_DEFAULT_MAX_BACKLIGHT - AMDGPU_DM_DEFAULT_MIN_BACKLIGHT) / 2) #define AUX_BL_DEFAULT_TRANSITION_TIME_MS 50 #if defined(CONFIG_BACKLIGHT_CLASS_DEVICE) ||\ @@ -3923,6 +3924,21 @@ static void amdgpu_dm_update_backlight_c return; amdgpu_acpi_get_backlight_caps(&caps); + + /* validate the firmware value is sane */ + if (caps.caps_valid) { + 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 || + spread > AMDGPU_DM_DEFAULT_MAX_BACKLIGHT || + spread < AMDGPU_DM_MIN_SPREAD) { + DRM_DEBUG_KMS("DM: Invalid backlight caps: min=%d, max=%d\n", + caps.min_input_signal, caps.max_input_signal); + caps.caps_valid = false; + } + } + if (caps.caps_valid) { dm->backlight_caps[bl_idx].caps_valid = true; if (caps.aux_support) Patches currently in stable-queue which might be from mario.limonciello@xxxxxxx are queue-5.15/drm-amd-display-validate-backlight-caps-are-sane.patch queue-5.15/acpi-bus-avoid-using-cppc-if-not-supported-by-firmwa.patch queue-5.15/drm-amd-display-round-calculated-vtotal.patch
