[PATCH 1/2] drm/amdgpu: Add "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]
Introduce the "max_bpc" connector property so the user can limit the
maximum bpc for the panel. It ranges from 8 to 16.

This doesn't directly set the preferred bpc for the panel but this
convetion is already in use for other drivers.

Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_display.c | 5 +++++
 drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h    | 2 ++
 2 files changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
index 7d6a36bca9dd..83dadf5b85e0 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
@@ -626,6 +626,11 @@ int amdgpu_display_modeset_create_props(struct amdgpu_device *adev)
 					 "dither",
 					 amdgpu_dither_enum_list, sz);
 
+	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;
+
 	if (amdgpu_device_has_dc_support(adev)) {
 		adev->mode_info.freesync_property =
 			drm_property_create_bool(adev->ddev, 0, "freesync");
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h
index 1627dd3413c7..c39af5d79608 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h
@@ -338,6 +338,8 @@ 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;
 	/* it is used to allow enablement of freesync mode */
 	struct drm_property *freesync_property;
 	/* it is used to know about display capability of freesync mode */
-- 
2.17.1