Re: [PATCH 02/14] drm/i915/dp: Return early if DSC not supported

[Jani Nikula <jani.nikula@linux.intel.com>]

On Tue, 17 Dec 2024, Jani Nikula <jani.nikula@linux.intel.com> wrote:
> On Tue, 17 Dec 2024, Ankit Nautiyal <ankit.k.nautiyal@intel.com> wrote:
>> Check for DSC support before computing link config with DSC.
>> For DP MST we are already doing the same.
>>
>> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
>> Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
>> ---
>>  drivers/gpu/drm/i915/display/intel_dp.c | 6 +++---
>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
>> index 908b9887f89b..dd2da9facaad 100644
>> --- a/drivers/gpu/drm/i915/display/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
>> @@ -2375,9 +2375,6 @@ int intel_dp_dsc_compute_config(struct intel_dp *intel_dp,
>>  		 intel_dp_supports_fec(intel_dp, connector, pipe_config) &&
>>  		 !intel_dp_is_uhbr(pipe_config));
>>  
>> -	if (!intel_dp_supports_dsc(intel_dp, connector, pipe_config))
>> -		return -EINVAL;
>> -
>>  	if (!intel_dp_dsc_supports_format(connector, pipe_config->output_format))
>>  		return -EINVAL;
>>  
>> @@ -2652,6 +2649,9 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
>>  			    str_yes_no(ret), str_yes_no(joiner_needs_dsc),
>>  			    str_yes_no(intel_dp->force_dsc_en));
>>  
>> +		if (!intel_dp_supports_dsc(intel_dp, connector, pipe_config))
>> +			return -EINVAL;
>> +
>
> The (pre-existing) problem with this is that we debug log we fall back
> to DSC, while we don't.
>
> Maybe we should do something like this instead, both in SST and MST code:

On second thought, this can also come as a follow-up later. I don't want
to block the series with this.

BR,
Jani.


>
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -2644,6 +2644,11 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
>  			dsc_needed = true;
>  	}
>  
> +	if (dsc_needed && !intel_dp_supports_dsc(connector, pipe_config)) {
> +		drm_dbg_kms(display->drm, "DSC required but not available.\n");
> +		return -EINVAL;
> +	}
> +
>  	if (dsc_needed) {
>  		drm_dbg_kms(display->drm,
>  			    "Try DSC (fallback=%s, joiner=%s, force=%s)\n",
>
> BR,
> Jani.
>
>>  		if (!intel_dp_compute_config_limits(intel_dp, pipe_config,
>>  						    respect_downstream_limits,
>>  						    true,

-- 
Jani Nikula, Intel