[PATCH 2/2] drm/amd/display: Support "max_bpc" connector property

[Nicholas Kazlauskas]

[Why]
Many panels support more than 8bpc but some modes are unavailable while
running at greater than 8bpc due to DP/HDMI bandwidth constraints.

Support for more than 8bpc was added recently in the driver but it's
defaults to the maximum supported bpc - locking out these modes.

This should be a user configurable option such that the user can select
what bpc configuration they would like.

[How]
Add support for getting and setting the property on the connector
in amdgpu_dm.

The maximum bpc is then limited by the value set by the user. The
default value is the lowest in the range, 8bpc. This was the old
default before the range was uncapped.

Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas at amd.com>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 15 +++++++++++++++
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h |  1 +
 2 files changed, 16 insertions(+)

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 c440d967db57..6184c5bc52e3 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -2417,8 +2417,14 @@ 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;
 
+	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);
+
 	switch (bpc) {
 	case 0:
 		/*
@@ -3001,6 +3007,9 @@ 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.freesync_property) {
 		dm_new_state->freesync_enable = val;
 		ret = 0;
@@ -3049,6 +3058,9 @@ 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.freesync_property) {
 		*val = dm_state->freesync_enable;
 		ret = 0;
@@ -3864,6 +3876,9 @@ 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);
 
 	if (connector_type == DRM_MODE_CONNECTOR_HDMIA ||
 	    connector_type == DRM_MODE_CONNECTOR_DisplayPort) {
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 23f2d05cf07e..afcb9842bb45 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
@@ -252,6 +252,7 @@ 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_enable;
 	bool freesync_capable;
-- 
2.17.1