[PATCH 1/2] drm/amdgpu: Add "max_bpc" connector property

Deucher, Alexander Alexander.Deucher at amd.com
Wed Nov 7 15:40:23 UTC 2018

FWIW there is a common property patch:


When should try and be compatible so we can transition.


From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> on behalf of Nicholas Kazlauskas <nicholas.kazlauskas at amd.com>
Sent: Wednesday, November 7, 2018 9:56:54 AM
To: amd-gfx at lists.freedesktop.org
Cc: Kazlauskas, Nicholas
Subject: [PATCH 1/2] drm/amdgpu: Add "max_bpc" connector property

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.

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)
                                          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 */

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