drm/amd: Query and use ACPI backlight caps

ACPI ATIF has a function called query
backlight transfer characteristics.  Among the
information returned by this function is
the minimum and maximum input signals for the
backlight

Call that function on ACPI init.  When DM
backlight device is updated, copy over the
backlight caps into DM, but only once.  Use
the backlight caps in the backlight-to-dc
calculation

Signed-off-by: David Francis <David.Francis@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
index 0512a9810913..19cd4626c3c0 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
@@ -84,6 +84,18 @@ struct dm_comressor_info {
 };
 
 /**
+ * struct amdgpu_dm_backlight_caps - Usable range of backlight values from ACPI
+ * @min_input_signal: minimum possible input in range 0-255
+ * @max_input_signal: maximum possible input in range 0-255
+ * @caps_valid: true if these values are from the ACPI interface
+ */
+struct amdgpu_dm_backlight_caps {
+	int min_input_signal;
+	int max_input_signal;
+	bool caps_valid;
+};
+
+/**
  * struct amdgpu_display_manager - Central amdgpu display manager device
  *
  * @dc: Display Core control structure
@@ -158,6 +170,7 @@ struct amdgpu_display_manager {
 	struct backlight_device *backlight_dev;
 
 	const struct dc_link *backlight_link;
+	struct amdgpu_dm_backlight_caps backlight_caps;
 
 	struct mod_freesync *freesync_module;