[PATCH] drm/amd/display: add a check for display depth validity

[Mikita Lipski]

On 2018-07-04 04:51 PM, Harry Wentland wrote:
> On 2018-07-04 04:40 PM, mikita.lipski at amd.com wrote:
>> From: Mikita Lipski <mikita.lipski at amd.com>
>>
>> [why]
>> HDMI 2.0 fails to validate 4K at 60 timing with 10 bpc
>> [how]
>> Adding a helper function that would verify if the display depth
>> assigned would pass a bandwidth validation.
>> Drop the display depth by one level till calculated pixel clk
>> is lower than maximum TMDS clk.
>>
>> Bugzilla: https://bugs.freedesktop.org/106959
>>
>> Signed-off-by: Mikita Lipski <mikita.lipski at amd.com>
>> ---
>>   drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 42 +++++++++++++++++++++++
>>   1 file changed, 42 insertions(+)
>>
>> 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 ed09e36..c572e86 100644
>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> @@ -2218,6 +2218,46 @@ get_output_color_space(const struct dc_crtc_timing *dc_crtc_timing)
>>   	return color_space;
>>   }
>>   
>> +static void reduce_mode_colour_depth(struct dc_crtc_timing *timing_out)
>> +{
>> +	if (timing_out->display_color_depth <= COLOR_DEPTH_888)
>> +		return;
>> +
>> +	timing_out->display_color_depth--;
>> +}
>> +
>> +static void check_if_display_depth_is_supported(struct dc_crtc_timing *timing_out,
> 
> Doesn't this update timing_out->display_color_depth? We should probably name this something else, maybe "pick_max_supported_color_depth" or something similar.
> 
> Harry
> 
The function reduce_mode_colour_depth introduced above is the one that 
modifies timing_out->display_color_depth.

Nick
>> +						const struct drm_display_info *info)
>> +{
>> +	int normalized_clk;
>> +	if (timing_out->display_color_depth <= COLOR_DEPTH_888)
>> +		return;
>> +	do {
>> +		normalized_clk = timing_out->pix_clk_khz;
>> +		/* YCbCr 4:2:0 requires additional adjustment of 1/2 */
>> +		if (timing_out->pixel_encoding == PIXEL_ENCODING_YCBCR420)
>> +			normalized_clk /= 2;
>> +		/* Adjusting pix clock following on HDMI spec based on colour depth */
>> +		switch (timing_out->display_color_depth) {
>> +		case COLOR_DEPTH_101010:
>> +			normalized_clk = (normalized_clk * 30) / 24;
>> +			break;
>> +		case COLOR_DEPTH_121212:
>> +			normalized_clk = (normalized_clk * 36) / 24;
>> +			break;
>> +		case COLOR_DEPTH_161616:
>> +			normalized_clk = (normalized_clk * 48) / 24;
>> +			break;
>> +		default:
>> +			return;
>> +		}
>> +		if (normalized_clk <= info->max_tmds_clock)
>> +			return;
>> +		reduce_mode_colour_depth(timing_out);
>> +
>> +	} while (timing_out->display_color_depth > COLOR_DEPTH_888);
>> +
>> +}
>>   /*****************************************************************************/
>>   
>>   static void
>> @@ -2273,6 +2313,8 @@ fill_stream_properties_from_drm_display_mode(struct dc_stream_state *stream,
>>   
>>   	stream->out_transfer_func->type = TF_TYPE_PREDEFINED;
>>   	stream->out_transfer_func->tf = TRANSFER_FUNCTION_SRGB;
>> +	if (stream->sink->sink_signal == SIGNAL_TYPE_HDMI_TYPE_A)
>> +		check_if_display_depth_is_supported(timing_out, info);
>>   }
>>   
>>   static void fill_audio_info(struct audio_info *audio_info,
>>