Re: [PATCH 3/4] drm/i915/dp: Limit compute config joining to pipes that can actually join

On 8/7/2026 6:04 PM, Jani Nikula wrote:
> Skip joining for pipes that can't work as joiner primary pipe for the
> number of pipes being joined. This limits the invalid combos early,
> instead of ending up with crtc_state->joiner_pipes that would fail
> during modeset. Before, crtc_state->joiner pipes could have ended up
> including pipes that do not exist on the platform.
>
> Cc: Ankit Nautiyal <[email protected]>
> Signed-off-by: Jani Nikula <[email protected]>

LGTM.

Reviewed-by: Ankit Nautiyal <[email protected]>

> ---
>   drivers/gpu/drm/i915/display/intel_dp.c     | 5 +++++
>   drivers/gpu/drm/i915/display/intel_dp_mst.c | 4 ++++
>   2 files changed, 9 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index e1604bc895e5..6b60e0a1c8ee 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -2910,6 +2910,7 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
>   			     struct drm_connector_state *conn_state,
>   			     bool respect_downstream_limits)
>   {
> +	struct intel_display *display = to_intel_display(encoder);
>   	struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
>   	struct intel_connector *connector =
>   		to_intel_connector(conn_state->connector);
> @@ -2924,6 +2925,10 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
>   		return -EINVAL;
>   
>   	for_each_joiner_candidate(connector, adjusted_mode, num_joined_pipes) {
> +		/* If the pipe can't be a joiner primary, skip early. */
> +		if (!(intel_joiner_valid_primary_pipe_mask(display, num_joined_pipes) & BIT(crtc->pipe)))
> +			continue;
> +
>   		/*
>   		 * NOTE:
>   		 * The crtc_state->joiner_pipes should have been set at the end
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> index 3be1643f8d03..379666692bc8 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -770,6 +770,10 @@ static int mst_stream_compute_config(struct intel_atomic_state *state,
>   		return ret;
>   
>   	for_each_joiner_candidate(connector, adjusted_mode, num_joined_pipes) {
> +		/* If the pipe can't be a joiner primary, skip early. */
> +		if (!(intel_joiner_valid_primary_pipe_mask(display, num_joined_pipes) & BIT(crtc->pipe)))
> +			continue;
> +
>   		if (num_joined_pipes > 1)
>   			pipe_config->joiner_pipes = GENMASK(crtc->pipe + num_joined_pipes - 1,
>   							    crtc->pipe);