[PATCH 1/2] drm/i915/dp_mst: Handle error during DSC BW overhead/slice calculation

[Kandpal, Suraj]

> -----Original Message-----
> From: Intel-gfx <intel-gfx-bounces at lists.freedesktop.org> On Behalf Of Imre
> Deak
> Sent: Wednesday, October 9, 2024 4:32 PM
> To: intel-gfx at lists.freedesktop.org
> Subject: [PATCH 1/2] drm/i915/dp_mst: Handle error during DSC BW
> overhead/slice calculation
> 
> The MST branch device may not support the number of DSC slices a mode
> requires, handle the error in this case.
> 
> Signed-off-by: Imre Deak <imre.deak at intel.com>

I feel this is a better implementation of the fix I had sent
LGTM,
Reviewed-by: Suraj Kandpal <suraj.kandpal at intel.com>

> ---
>  drivers/gpu/drm/i915/display/intel_dp_mst.c | 39 ++++++++++++++-------
>  1 file changed, 27 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> index 4765bda154c15..2822ae1160034 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -90,27 +90,19 @@ static int intel_dp_mst_max_dpt_bpp(const struct
> intel_crtc_state *crtc_state,
> 
>  static int intel_dp_mst_bw_overhead(const struct intel_crtc_state
> *crtc_state,
>  				    const struct intel_connector *connector,
> -				    bool ssc, bool dsc, int bpp_x16)
> +				    bool ssc, int dsc_slice_count, int bpp_x16)
>  {
>  	const struct drm_display_mode *adjusted_mode =
>  		&crtc_state->hw.adjusted_mode;
>  	unsigned long flags = DRM_DP_BW_OVERHEAD_MST;
> -	int dsc_slice_count = 0;
>  	int overhead;
> 
>  	flags |= intel_dp_is_uhbr(crtc_state) ?
> DRM_DP_BW_OVERHEAD_UHBR : 0;
>  	flags |= ssc ? DRM_DP_BW_OVERHEAD_SSC_REF_CLK : 0;
>  	flags |= crtc_state->fec_enable ? DRM_DP_BW_OVERHEAD_FEC : 0;
> 
> -	if (dsc) {
> -		int num_joined_pipes =
> intel_crtc_num_joined_pipes(crtc_state);
> -
> +	if (dsc_slice_count)
>  		flags |= DRM_DP_BW_OVERHEAD_DSC;
> -		dsc_slice_count = intel_dp_dsc_get_slice_count(connector,
> -							       adjusted_mode-
> >clock,
> -							       adjusted_mode-
> >hdisplay,
> -
> num_joined_pipes);
> -	}
> 
>  	overhead = drm_dp_bw_overhead(crtc_state->lane_count,
>  				      adjusted_mode->hdisplay,
> @@ -156,6 +148,19 @@ static int intel_dp_mst_calc_pbn(int pixel_clock, int
> bpp_x16, int bw_overhead)
>  	return DIV_ROUND_UP(effective_data_rate * 64, 54 * 1000);  }
> 
> +static int intel_dp_mst_dsc_get_slice_count(const struct intel_connector
> *connector,
> +					    const struct intel_crtc_state
> *crtc_state) {
> +	const struct drm_display_mode *adjusted_mode =
> +		&crtc_state->hw.adjusted_mode;
> +	int num_joined_pipes = intel_crtc_num_joined_pipes(crtc_state);
> +
> +	return intel_dp_dsc_get_slice_count(connector,
> +					    adjusted_mode->clock,
> +					    adjusted_mode->hdisplay,
> +					    num_joined_pipes);
> +}
> +
>  static int intel_dp_mst_find_vcpi_slots_for_bpp(struct intel_encoder
> *encoder,
>  						struct intel_crtc_state
> *crtc_state,
>  						int max_bpp,
> @@ -175,6 +180,7 @@ static int
> intel_dp_mst_find_vcpi_slots_for_bpp(struct intel_encoder *encoder,
>  	const struct drm_display_mode *adjusted_mode =
>  		&crtc_state->hw.adjusted_mode;
>  	int bpp, slots = -EINVAL;
> +	int dsc_slice_count = 0;
>  	int max_dpt_bpp;
>  	int ret = 0;
> 
> @@ -206,6 +212,15 @@ static int
> intel_dp_mst_find_vcpi_slots_for_bpp(struct intel_encoder *encoder,
>  	drm_dbg_kms(&i915->drm, "Looking for slots in range min bpp %d
> max bpp %d\n",
>  		    min_bpp, max_bpp);
> 
> +	if (dsc) {
> +		dsc_slice_count =
> intel_dp_mst_dsc_get_slice_count(connector, crtc_state);
> +		if (!dsc_slice_count) {
> +			drm_dbg_kms(&i915->drm, "Can't get valid DSC slice
> count\n");
> +
> +			return -ENOSPC;
> +		}
> +	}
> +
>  	for (bpp = max_bpp; bpp >= min_bpp; bpp -= step) {
>  		int local_bw_overhead;
>  		int remote_bw_overhead;
> @@ -219,9 +234,9 @@ static int
> intel_dp_mst_find_vcpi_slots_for_bpp(struct intel_encoder *encoder,
>  					       intel_dp_output_bpp(crtc_state-
> >output_format, bpp));
> 
>  		local_bw_overhead = intel_dp_mst_bw_overhead(crtc_state,
> connector,
> -							     false, dsc,
> link_bpp_x16);
> +							     false,
> dsc_slice_count, link_bpp_x16);
>  		remote_bw_overhead =
> intel_dp_mst_bw_overhead(crtc_state, connector,
> -							      true, dsc,
> link_bpp_x16);
> +							      true,
> dsc_slice_count, link_bpp_x16);
> 
>  		intel_dp_mst_compute_m_n(crtc_state, connector,
>  					 local_bw_overhead,
> --
> 2.44.2