Re: [PATCH 4/6] drm/i915/mst: handle mst pbn_div in intel_dp_mtp_tu_compute_config()

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

On Wed, Jan 29, 2025 at 04:46:36PM +0200, Jani Nikula wrote:
> Move mst_state->pbn_div calculation to intel_dp_mtp_tu_compute_config()
> to allow further refactoring.
> 
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_dp_mst.c | 31 ++++++++++-----------
>  1 file changed, 14 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> index ea1b05224c06..8786c8751c82 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -216,15 +216,25 @@ int intel_dp_mtp_tu_compute_config(struct intel_dp *intel_dp,
>  {
>  	struct intel_display *display = to_intel_display(intel_dp);
>  	struct drm_atomic_state *state = crtc_state->uapi.state;
> +	struct drm_dp_mst_topology_state *mst_state = NULL;
>  	struct intel_connector *connector =
>  		to_intel_connector(conn_state->connector);
>  	const struct drm_display_mode *adjusted_mode =
>  		&crtc_state->hw.adjusted_mode;
> -	fixed20_12 pbn_div;
> +	bool is_mst = intel_dp->is_mst;
>  	int bpp, slots = -EINVAL;
>  	int dsc_slice_count = 0;
>  	int max_dpt_bpp;
>  
> +	if (is_mst) {
> +		mst_state = drm_atomic_get_mst_topology_state(state, &intel_dp->mst_mgr);
> +		if (IS_ERR(mst_state))
> +			return PTR_ERR(mst_state);
> +
> +		mst_state->pbn_div = drm_dp_get_vc_payload_bw(crtc_state->port_clock,
> +							      crtc_state->lane_count);
> +	}
> +

This could've been in the if (intel_dp->is_mst) block, since SST doesn't
use pbn_div. In any case the patch is correct:

Reviewed-by: Imre Deak <imre.deak@intel.com>

>  	if (dsc) {
>  		if (!intel_dp_supports_fec(intel_dp, connector, crtc_state))
>  			return -EINVAL;
> @@ -232,9 +242,6 @@ int intel_dp_mtp_tu_compute_config(struct intel_dp *intel_dp,
>  		crtc_state->fec_enable = !intel_dp_is_uhbr(crtc_state);
>  	}
>  
> -	pbn_div = drm_dp_get_vc_payload_bw(crtc_state->port_clock,
> -					   crtc_state->lane_count);
> -
>  	max_dpt_bpp = intel_dp_mst_max_dpt_bpp(crtc_state, dsc);
>  	if (max_bpp > max_dpt_bpp) {
>  		drm_dbg_kms(display->drm, "Limiting bpp to max DPT bpp (%d -> %d)\n",
> @@ -270,7 +277,7 @@ int intel_dp_mtp_tu_compute_config(struct intel_dp *intel_dp,
>  					 link_bpp_x16,
>  					 &crtc_state->dp_m_n);
>  
> -		if (intel_dp->is_mst) {
> +		if (is_mst) {
>  			int remote_bw_overhead;
>  			int remote_tu;
>  			fixed20_12 pbn;
> @@ -295,7 +302,7 @@ int intel_dp_mtp_tu_compute_config(struct intel_dp *intel_dp,
>  			pbn.full = dfixed_const(intel_dp_mst_calc_pbn(adjusted_mode->crtc_clock,
>  								      link_bpp_x16,
>  								      remote_bw_overhead));
> -			remote_tu = DIV_ROUND_UP(pbn.full, pbn_div.full);
> +			remote_tu = DIV_ROUND_UP(pbn.full, mst_state->pbn_div.full);
>  
>  			/*
>  			 * Aligning the TUs ensures that symbols consisting of multiple
> @@ -313,7 +320,7 @@ int intel_dp_mtp_tu_compute_config(struct intel_dp *intel_dp,
>  			 * allocated for the whole path and the TUs allocated for the
>  			 * first branch device's link also applies here.
>  			 */
> -			pbn.full = remote_tu * pbn_div.full;
> +			pbn.full = remote_tu * mst_state->pbn_div.full;
>  
>  			drm_WARN_ON(display->drm, remote_tu < crtc_state->dp_m_n.tu);
>  			crtc_state->dp_m_n.tu = remote_tu;
> @@ -365,16 +372,6 @@ static int mst_stream_find_vcpi_slots_for_bpp(struct intel_dp *intel_dp,
>  					      struct drm_connector_state *conn_state,
>  					      int step, bool dsc)
>  {
> -	struct drm_atomic_state *state = crtc_state->uapi.state;
> -	struct drm_dp_mst_topology_state *mst_state;
> -
> -	mst_state = drm_atomic_get_mst_topology_state(state, &intel_dp->mst_mgr);
> -	if (IS_ERR(mst_state))
> -		return PTR_ERR(mst_state);
> -
> -	mst_state->pbn_div = drm_dp_get_vc_payload_bw(crtc_state->port_clock,
> -						      crtc_state->lane_count);
> -
>  	return intel_dp_mtp_tu_compute_config(intel_dp, crtc_state, conn_state,
>  					      min_bpp, max_bpp, step, dsc);
>  }
> -- 
> 2.39.5
>