Re: [PATCH 14/16] drm/i915/dp: Add helpers for joiner candidate loops

[Imre Deak <imre.deak@intel.com>]

On Wed, Jan 28, 2026 at 07:36:34PM +0530, Ankit Nautiyal wrote:
> Introduce for_each_joiner_candidate(), intel_dp_pick_joiner_candidate() and
> intel_dp_joiner_candidate_valid() to remove duplicated joiner enumeration
> and validity checks across DP SST and MST paths.
> 
> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_dp.c     | 37 ++++++++-------------
>  drivers/gpu/drm/i915/display/intel_dp.h     | 31 +++++++++++++++++
>  drivers/gpu/drm/i915/display/intel_dp_mst.c | 37 ++++++++-------------
>  3 files changed, 59 insertions(+), 46 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index c1ff92367808..9eba8f90bc90 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -1529,23 +1529,19 @@ intel_dp_mode_valid(struct drm_connector *_connector,
>  	 * Because of this dependency cycle, the only correct approach is to iterate
>  	 * over candidate pipe counts and evaluate each combination.
>  	 */
> -	for (num_pipes = 0; num_pipes < I915_MAX_PIPES; num_pipes++) {
> +	for_each_joiner_candidate(num_pipes) {
>  		int dsc_slice_count = 0;
>  
>  		status = MODE_CLOCK_HIGH;
>  
> -		if (num_pipes == 0) {
> -			if (!connector->force_joined_pipes)
> -				continue;
> -			num_joined_pipes = connector->force_joined_pipes;
> -		} else {
> -			num_joined_pipes = num_pipes;
> -		}
> -
> -		if (!intel_dp_can_join(display, num_joined_pipes))
> +		if (!intel_dp_pick_joiner_candidate(num_pipes,
> +						    connector->force_joined_pipes,
> +						    &num_joined_pipes))
>  			continue;
>  
> -		if (mode->hdisplay > num_joined_pipes * intel_dp_max_hdisplay_per_pipe(display))
> +		if (!intel_dp_joiner_candidate_valid(display,
> +						     mode->hdisplay,
> +						     num_joined_pipes))
>  			continue;

By not allowing to fallback from a forced joined-pipe to a non-forced
one as mentioned earlier (and so you'd iterate num_pipes = 1 ..
I915_MAX_PIPES - 1) you could fold all the above into a
for_each_joiner_candidate(connector, mode, num_pipes) helper and with
that yes, the iterator would make sense simplifying things a lot.

>  
>  		status = intel_pfit_mode_valid(display, mode, output_format, num_joined_pipes);
> @@ -2938,20 +2934,15 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
>  	    !intel_dp_supports_fec(intel_dp, connector, crtc_state))
>  		return -EINVAL;
>  
> -	for (num_pipes = 0; num_pipes < I915_MAX_PIPES; num_pipes++) {
> -		if (num_pipes == 0) {
> -			if (!connector->force_joined_pipes)
> -				continue;
> -			num_joined_pipes = connector->force_joined_pipes;
> -		} else {
> -			num_joined_pipes = num_pipes;
> -		}
> -
> -		if (!intel_dp_can_join(display, num_joined_pipes))
> +	for_each_joiner_candidate(num_pipes) {
> +		if (!intel_dp_pick_joiner_candidate(num_pipes,
> +						    connector->force_joined_pipes,
> +						    &num_joined_pipes))
>  			continue;
>  
> -		if (adjusted_mode->hdisplay >
> -		    num_joined_pipes * intel_dp_max_hdisplay_per_pipe(display))
> +		if (!intel_dp_joiner_candidate_valid(display,
> +						     adjusted_mode->hdisplay,
> +						     num_joined_pipes))
>  			continue;
>  
>  		/*
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.h b/drivers/gpu/drm/i915/display/intel_dp.h
> index beef480b7672..111a5d4b3992 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.h
> +++ b/drivers/gpu/drm/i915/display/intel_dp.h
> @@ -234,4 +234,35 @@ bool intel_dp_dotclk_valid(struct intel_display *display,
>  			   int dsc_slice_count,
>  			   int num_joined_pipes);
>  
> +#define for_each_joiner_candidate(__num_pipes) \
> +	for ((__num_pipes) = 0; (__num_pipes) < (I915_MAX_PIPES); (__num_pipes)++)
> +
> +static inline bool intel_dp_pick_joiner_candidate(int num_pipes,
> +						  int force_joined_pipes,
> +						  int *num_joined_pipes)
> +{
> +	if (num_pipes == 0) {
> +		if (!force_joined_pipes)
> +			return false;
> +		*num_joined_pipes = force_joined_pipes;
> +	} else {
> +		*num_joined_pipes = num_pipes;
> +	}
> +
> +	return true;
> +}
> +
> +static inline bool intel_dp_joiner_candidate_valid(struct intel_display *display,
> +						   int hdisplay,
> +						   int num_joined_pipes)
> +{
> +	if (!intel_dp_can_join(display, num_joined_pipes))
> +		return false;
> +
> +	if (hdisplay > num_joined_pipes * intel_dp_max_hdisplay_per_pipe(display))
> +		return false;
> +
> +	return true;
> +}
> +
>  #endif /* __INTEL_DP_H__ */
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> index bdf2f09fa03e..005efcb5d2bf 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -701,24 +701,19 @@ static int mst_stream_compute_config(struct intel_encoder *encoder,
>  	pipe_config->output_format = INTEL_OUTPUT_FORMAT_RGB;
>  	pipe_config->has_pch_encoder = false;
>  
> -	for (num_pipes = 0; num_pipes < I915_MAX_PIPES; num_pipes++) {
> +	for_each_joiner_candidate(num_pipes) {
>  		int dsc_slice_count = 0;
>  
>  		ret = -EINVAL;
>  
> -		if (num_pipes == 0) {
> -			if (!connector->force_joined_pipes)
> -				continue;
> -			num_joined_pipes = connector->force_joined_pipes;
> -		} else {
> -			num_joined_pipes = num_pipes;
> -		}
> -
> -		if (!intel_dp_can_join(display, num_joined_pipes))
> +		if (!intel_dp_pick_joiner_candidate(num_pipes,
> +						    connector->force_joined_pipes,
> +						    &num_joined_pipes))
>  			continue;
>  
> -		if (adjusted_mode->hdisplay >
> -		    num_joined_pipes * intel_dp_max_hdisplay_per_pipe(display))
> +		if (!intel_dp_joiner_candidate_valid(display,
> +						     adjusted_mode->hdisplay,
> +						     num_joined_pipes))
>  			continue;
>  
>  		if (num_joined_pipes > 1)
> @@ -1535,23 +1530,19 @@ mst_connector_mode_valid_ctx(struct drm_connector *_connector,
>  		return 0;
>  	}
>  
> -	for (num_pipes = 0; num_pipes < I915_MAX_PIPES; num_pipes++) {
> +	for_each_joiner_candidate(num_pipes) {
>  		int dsc_slice_count = 0;
>  
>  		*status = MODE_CLOCK_HIGH;
>  
> -		if (num_pipes == 0) {
> -			if (!connector->force_joined_pipes)
> -				continue;
> -			num_joined_pipes = connector->force_joined_pipes;
> -		} else {
> -			num_joined_pipes = num_pipes;
> -		}
> -
> -		if (!intel_dp_can_join(display, num_joined_pipes))
> +		if (!intel_dp_pick_joiner_candidate(num_pipes,
> +						    connector->force_joined_pipes,
> +						    &num_joined_pipes))
>  			continue;
>  
> -		if (mode->hdisplay > num_joined_pipes * intel_dp_max_hdisplay_per_pipe(display))
> +		if (!intel_dp_joiner_candidate_valid(display,
> +						     mode->hdisplay,
> +						     num_joined_pipes))
>  			continue;
>  
>  		if (intel_dp_has_dsc(connector) &&
> -- 
> 2.45.2
>