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Subject: Re: [PATCH v4 17/17] drm/amd/display: Add handling for new "Broadcast
 RGB" property
To:     Pekka Paalanen <ppaalanen@gmail.com>
Cc:     amd-gfx@lists.freedesktop.org, tzimmermann@suse.de,
        intel-gfx@lists.freedesktop.org, sunpeng.li@amd.com,
        dri-devel@lists.freedesktop.org, joonas.lahtinen@linux.intel.com,
        maarten.lankhorst@linux.intel.com, linux-kernel@vger.kernel.org,
        mripard@kernel.org, airlied@linux.ie, jani.nikula@linux.intel.com,
        daniel@ffwll.ch, rodrigo.vivi@intel.com, alexander.deucher@amd.com,
        harry.wentland@amd.com, christian.koenig@amd.com
References: <20210618091116.14428-1-wse@tuxedocomputers.com>
 <20210618091116.14428-18-wse@tuxedocomputers.com>
 <20210622102955.1e0488b1@eldfell>
From:   Werner Sembach <wse@tuxedocomputers.com>
Message-ID: <ded3d448-4837-f38d-9878-f5d764712db7@tuxedocomputers.com>
Date:   Tue, 22 Jun 2021 11:28:57 +0200
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Am 22.06.21 um 09:29 schrieb Pekka Paalanen:
> On Fri, 18 Jun 2021 11:11:16 +0200
> Werner Sembach <wse@tuxedocomputers.com> wrote:
>
>> This commit implements the "Broadcast RGB" drm property for the AMD GPU
>> driver.
>>
>> Signed-off-by: Werner Sembach <wse@tuxedocomputers.com>
>> ---
>>  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 22 ++++++++++++++-----
>>  .../display/amdgpu_dm/amdgpu_dm_mst_types.c   |  4 ++++
>>  2 files changed, 21 insertions(+), 5 deletions(-)
>>
>> 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 9ffd2f9d3d75..c5dbf948a47a 100644
>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> @@ -5252,7 +5252,8 @@ get_aspect_ratio(const struct drm_display_mode *mode_in)
>>  }
>>  
>>  static enum dc_color_space
>> -get_output_color_space(const struct dc_crtc_timing *dc_crtc_timing)
>> +get_output_color_space(const struct dc_crtc_timing *dc_crtc_timing,
>> +		       enum drm_mode_color_range preferred_color_range)
>>  {
>>  	enum dc_color_space color_space = COLOR_SPACE_SRGB;
>>  
>> @@ -5267,13 +5268,17 @@ get_output_color_space(const struct dc_crtc_timing *dc_crtc_timing)
>>  		 * respectively
>>  		 */
>>  		if (dc_crtc_timing->pix_clk_100hz > 270300) {
>> -			if (dc_crtc_timing->flags.Y_ONLY)
>> +			if (dc_crtc_timing->flags.Y_ONLY
>> +					|| preferred_color_range ==
>> +						DRM_MODE_COLOR_RANGE_LIMITED_16_235)
>>  				color_space =
>>  					COLOR_SPACE_YCBCR709_LIMITED;
>>  			else
>>  				color_space = COLOR_SPACE_YCBCR709;
> Hi,
>
> does this mean that amdgpu would be using a property named "Broadcast
> RGB" to control the range of YCbCr too?

Yes, because I avoided creating a new property, but I'm not really happy with it either.

Possibility 1: Use "Broadcast RGB" for Y'CbCr too and clarify in documentation
??? - still confusing name
??? - limited does not mean something a little bit different for Y'CbCr and not strictly 16-235:
https://www.kernel.org/doc/html/v5.12/userspace-api/media/v4l/colorspaces-defs.html#c.V4L.v4l2_quantization , but name
of option is given by preexisting property

Possibility 2: Deprecate "Broadcast RGB" and a a more neutral sounding "preferred color range", with the more neutral
sounding "limited" option instead of "Limited 16:235"
??? - What's the relation between the 2? pq mentioned on the amdgpu gitlab that there is a posibility for userspace to
have only the new or the old one shown
??? - Alternatively ignore "Broadcast RGB" when "preferred color range" is set and have them coexist?

>
> That is surprising. If this is truly wanted, then the documentation of
> "Broadcast RGB" must say that it applies to YCbCr too.
>
> Does amdgpu do the same as intel wrt. to the question about whose
> responsibility it is to make the pixels at the connector to match the
> set range?

I guess the kernel driver does the conversion, but i have to check for both.

For Intel I did not change the behavior of Boradcast RGB, but i think it's not clearly specified in the docs where the
conversion happens.

>
>
> Thanks,
> pq
>
>>  		} else {
>> -			if (dc_crtc_timing->flags.Y_ONLY)
>> +			if (dc_crtc_timing->flags.Y_ONLY
>> +					|| preferred_color_range ==
>> +						DRM_MODE_COLOR_RANGE_LIMITED_16_235)
>>  				color_space =
>>  					COLOR_SPACE_YCBCR601_LIMITED;
>>  			else
>> @@ -5283,7 +5288,10 @@ get_output_color_space(const struct dc_crtc_timing *dc_crtc_timing)
>>  	}
>>  	break;
>>  	case PIXEL_ENCODING_RGB:
>> -		color_space = COLOR_SPACE_SRGB;
>> +		if (preferred_color_range == DRM_MODE_COLOR_RANGE_LIMITED_16_235)
>> +			color_space = COLOR_SPACE_SRGB_LIMITED;
>> +		else
>> +			color_space = COLOR_SPACE_SRGB;
>>  		break;
>>  
>>  	default:
>> @@ -5429,7 +5437,10 @@ static void fill_stream_properties_from_drm_display_mode(
>>  
>>  	timing_out->aspect_ratio = get_aspect_ratio(mode_in);
>>  
>> -	stream->output_color_space = get_output_color_space(timing_out);
>> +	stream->output_color_space = get_output_color_space(timing_out,
>> +							    connector_state ?
>> +							    connector_state->preferred_color_range :
>> +							    DRM_MODE_COLOR_RANGE_UNSET);
>>  
>>  	stream->out_transfer_func->type = TF_TYPE_PREDEFINED;
>>  	stream->out_transfer_func->tf = TRANSFER_FUNCTION_SRGB;
>> @@ -7780,6 +7791,7 @@ void amdgpu_dm_connector_init_helper(struct amdgpu_display_manager *dm,
>>  		drm_connector_attach_active_bpc_property(&aconnector->base, 8, 16);
>>  		drm_connector_attach_preferred_color_format_property(&aconnector->base);
>>  		drm_connector_attach_active_color_format_property(&aconnector->base);
>> +		drm_connector_attach_preferred_color_range_property(&aconnector->base);
>>  		drm_connector_attach_active_color_range_property(&aconnector->base);
>>  	}
>>  
>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
>> index 2563788ba95a..80e1389fd0ec 100644
>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
>> @@ -421,6 +421,10 @@ dm_dp_add_mst_connector(struct drm_dp_mst_topology_mgr *mgr,
>>  	if (connector->active_color_format_property)
>>  		drm_connector_attach_active_color_format_property(&aconnector->base);
>>  
>> +	connector->preferred_color_range_property = master->base.preferred_color_range_property;
>> +	if (connector->preferred_color_range_property)
>> +		drm_connector_attach_preferred_color_range_property(&aconnector->base);
>> +
>>  	connector->active_color_range_property = master->base.active_color_range_property;
>>  	if (connector->active_color_range_property)
>>  		drm_connector_attach_active_color_range_property(&aconnector->base);
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