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

[Harry Wentland]

On 2018-07-04 04:57 PM, Mikita Lipski wrote:
> 
> 
> 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.
> 

But check_if_display_depth_is_supported here calls reduce_mode_color_depth, so does more than just "check". :)

Harry

> 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,
>>>