drm/amd/display: Switch the custom "max bpc" property to the DRM prop

[Why]
The custom "max bpc" property was added to limit color depth while the
DRM one was still being merged. It's been a few kernel versions since
then and this TODO was still sticking around.

[How]
Attach the DRM max bpc property to the connector and drop all of our
custom property management. Set the max bpc to 8 by default since
DRM defaults to the max in the range which would be 16 in this case.

No behavioral changes are intended with this patch, it should just be
a refactor.

v2: Don't force 8bpc when no state is given

Cc: Leo Li <sunpeng.li@amd.com>
Cc: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_display.c

@@ -631,10 +631,6 @@ int amdgpu_display_modeset_create_props(struct amdgpu_device *adev)
 					 amdgpu_dither_enum_list, sz);
 
 	if (amdgpu_device_has_dc_support(adev)) {
-		adev->mode_info.max_bpc_property =
-			drm_property_create_range(adev->ddev, 0, "max bpc", 8, 16);
-		if (!adev->mode_info.max_bpc_property)
-			return -ENOMEM;
 		adev->mode_info.abm_level_property =
 			drm_property_create_range(adev->ddev, 0,
 						"abm level", 0, 4);

drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h

@@ -331,8 +331,6 @@ struct amdgpu_mode_info {
 	struct drm_property *audio_property;
 	/* FMT dithering */
 	struct drm_property *dither_property;
-	/* maximum number of bits per channel for monitor color */
-	struct drm_property *max_bpc_property;
 	/* Adaptive Backlight Modulation (power feature) */
 	struct drm_property *abm_level_property;
 	/* hardcoded DFP edid from BIOS */

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

@@ -2969,14 +2969,14 @@ static void update_stream_scaling_settings(const struct drm_display_mode *mode,
 static enum dc_color_depth
 convert_color_depth_from_display_info(const struct drm_connector *connector)
 {
-	struct dm_connector_state *dm_conn_state =
-		to_dm_connector_state(connector->state);
 	uint32_t bpc = connector->display_info.bpc;
 
-	/* TODO: Remove this when there's support for max_bpc in drm */
-	if (dm_conn_state && bpc > dm_conn_state->max_bpc)
-		/* Round down to nearest even number. */
-		bpc = dm_conn_state->max_bpc - (dm_conn_state->max_bpc & 1);
+	/* TODO: Use passed in state instead of the current state. */
+	if (connector->state) {
+		bpc = connector->state->max_bpc;
+		/* Round down to the nearest even number. */
+		bpc = bpc - (bpc & 1);
+	}
 
 	switch (bpc) {
 	case 0:
@@ -3618,9 +3618,6 @@ int amdgpu_dm_connector_atomic_set_property(struct drm_connector *connector,
 	} else if (property == adev->mode_info.underscan_property) {
 		dm_new_state->underscan_enable = val;
 		ret = 0;
-	} else if (property == adev->mode_info.max_bpc_property) {
-		dm_new_state->max_bpc = val;
-		ret = 0;
 	} else if (property == adev->mode_info.abm_level_property) {
 		dm_new_state->abm_level = val;
 		ret = 0;
@@ -3666,9 +3663,6 @@ int amdgpu_dm_connector_atomic_get_property(struct drm_connector *connector,
 	} else if (property == adev->mode_info.underscan_property) {
 		*val = dm_state->underscan_enable;
 		ret = 0;
-	} else if (property == adev->mode_info.max_bpc_property) {
-		*val = dm_state->max_bpc;
-		ret = 0;
 	} else if (property == adev->mode_info.abm_level_property) {
 		*val = dm_state->abm_level;
 		ret = 0;
@@ -3725,7 +3719,6 @@ void amdgpu_dm_connector_funcs_reset(struct drm_connector *connector)
 		state->underscan_enable = false;
 		state->underscan_hborder = 0;
 		state->underscan_vborder = 0;
-		state->max_bpc = 8;
 
 		__drm_atomic_helper_connector_reset(connector, &state->base);
 	}
@@ -3751,7 +3744,6 @@ amdgpu_dm_connector_atomic_duplicate_state(struct drm_connector *connector)
 	new_state->underscan_enable = state->underscan_enable;
 	new_state->underscan_hborder = state->underscan_hborder;
 	new_state->underscan_vborder = state->underscan_vborder;
-	new_state->max_bpc = state->max_bpc;
 
 	return &new_state->base;
 }
@@ -4672,9 +4664,12 @@ void amdgpu_dm_connector_init_helper(struct amdgpu_display_manager *dm,
 	drm_object_attach_property(&aconnector->base.base,
 				adev->mode_info.underscan_vborder_property,
 				0);
-	drm_object_attach_property(&aconnector->base.base,
-				adev->mode_info.max_bpc_property,
-				0);
+
+	drm_connector_attach_max_bpc_property(&aconnector->base, 8, 16);
+
+	/* This defaults to the max in the range, but we want 8bpc. */
+	aconnector->base.state->max_bpc = 8;
+	aconnector->base.state->max_requested_bpc = 8;
 
 	if (connector_type == DRM_MODE_CONNECTOR_eDP &&
 	    dc_is_dmcu_initialized(adev->dm.dc)) {

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

@@ -304,7 +304,6 @@ struct dm_connector_state {
 	enum amdgpu_rmx_type scaling;
 	uint8_t underscan_vborder;
 	uint8_t underscan_hborder;
-	uint8_t max_bpc;
 	bool underscan_enable;
 	bool freesync_capable;
 	uint8_t abm_level;