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

[Wentland, Harry]

On 2018-11-07 9:56 a.m., Nicholas Kazlauskas wrote:
> [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.

covetion -> convention

Maybe mention that this mirrors the behavior used by the i915 driver so people are not left guessing.

Harry

> 
> 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 */
>