[PATCH 4.19 027/118] drm/amdgpu: Add amdgpu "max bpc" connector property (v2)

From: Greg Kroah-Hartman
Date: Tue Dec 11 2018 - 10:55:00 EST

4.19-stable review patch. If anyone has any objections, please let me know.


[ Upstream commit 69756c6ff0de478c10100481f16c966dde3b5339 ]

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
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.

This patch introduces the "max bpc" amdgpu driver specific connector
property so the user can limit the maximum bpc. It ranges from 8 to 16.

This doesn't directly set the preferred bpc for the panel since it
follows Intel's existing driver conventions.

This proprety should be removed once common drm support for max bpc

v2: rebase on upstream (Alex)

Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@xxxxxxx>
Acked-by: Alex Deucher <alexander.deucher@xxxxxxx>
Reviewed-by: Harry Wentland <harry.wentland@xxxxxxx>
Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
drivers/gpu/drm/amd/amdgpu/amdgpu_display.c | 7 +++++++
drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h | 2 ++
2 files changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
index 6748cd7fc129..686a26de50f9 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
@@ -626,6 +626,13 @@ 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;
+ }
return 0;

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h
index b9e9e8b02fb7..d1b4d9b6aae0 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h
@@ -339,6 +339,8 @@ 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;
/* hardcoded DFP edid from BIOS */
struct edid *bios_hardcoded_edid;
int bios_hardcoded_edid_size;