Re: [PATCH 29/29] drm/i915: Query compressed bpp properly using correct DPCD and DP Spec info

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> -----Original Message-----
> From: Intel-gfx <intel-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of Imre
> Deak
> Sent: Tuesday, October 24, 2023 6:39 AM
> To: intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> Subject:  [PATCH 29/29] drm/i915: Query compressed bpp properly
> using correct DPCD and DP Spec info
> 
> From: Stanislav Lisovskiy <stanislav.lisovskiy@xxxxxxxxx>
> 
> Currently we seem to be using wrong DPCD register for reading compressed
> bpps, reading min/max input bpc instead of compressed bpp.
> Fix that, so that we now apply min/max compressed bpp limitations we get
> from DP Spec Table 2-157 DP v2.0 and/or correspondent DPCD register
> DP_DSC_MAX_BITS_PER_PIXEL_LOW/HIGH.
> 
> This might also allow us to get rid of an ugly compressed bpp recalculation,
> which we had to add to make some MST hubs usable.
> 
> v2: - Fix operator precedence
> v3: - Added debug info about compressed bpps
> v4: - Don't try to intersect Sink input bpp and compressed bpps.
> v5: - Decrease step while looking for suitable compressed bpp to
>       accommodate.
> v6: - Use helper for getting min and max compressed_bpp (Ankit)
> v7: - Fix checkpatch warning (Ankit)
> 
> Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@xxxxxxxxx>
> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@xxxxxxxxx>
> ---

Reviewed-by: Arun R Murthy <arun.r.murthy@xxxxxxxxx>

Thanks and Regards,
Arun R Murthy
-------------------

>  drivers/gpu/drm/i915/display/intel_dp.c     | 20 +++++---
>  drivers/gpu/drm/i915/display/intel_dp.h     |  4 ++
>  drivers/gpu/drm/i915/display/intel_dp_mst.c | 54 ++++++++++-----------
>  3 files changed, 41 insertions(+), 37 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> b/drivers/gpu/drm/i915/display/intel_dp.c
> index 969f19484c53c..c926478621753 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -1811,7 +1811,7 @@ u16
> intel_dp_dsc_max_sink_compressed_bppx16(const struct intel_connector
> *connec
>  	return 0;
>  }
> 
> -static int dsc_sink_min_compressed_bpp(struct intel_crtc_state *pipe_config)
> +int intel_dp_dsc_sink_min_compressed_bpp(struct intel_crtc_state
> +*pipe_config)
>  {
>  	/* From Mandatory bit rate range Support Table 2-157 (DP v2.0) */
>  	switch (pipe_config->output_format) {
> @@ -1828,9 +1828,9 @@ static int dsc_sink_min_compressed_bpp(struct
> intel_crtc_state *pipe_config)
>  	return 0;
>  }
> 
> -static int dsc_sink_max_compressed_bpp(const struct intel_connector
> *connector,
> -				       struct intel_crtc_state *pipe_config,
> -				       int bpc)
> +int intel_dp_dsc_sink_max_compressed_bpp(const struct intel_connector
> *connector,
> +					 struct intel_crtc_state *pipe_config,
> +					 int bpc)
>  {
>  	return intel_dp_dsc_max_sink_compressed_bppx16(connector,
>  						       pipe_config, bpc) >> 4;
> @@ -1944,12 +1944,14 @@ static int dsc_compute_compressed_bpp(struct
> intel_dp *intel_dp,
>  	int dsc_joiner_max_bpp;
> 
>  	dsc_src_min_bpp = dsc_src_min_compressed_bpp();
> -	dsc_sink_min_bpp = dsc_sink_min_compressed_bpp(pipe_config);
> +	dsc_sink_min_bpp =
> intel_dp_dsc_sink_min_compressed_bpp(pipe_config);
>  	dsc_min_bpp = max(dsc_src_min_bpp, dsc_sink_min_bpp);
>  	dsc_min_bpp = max(dsc_min_bpp, to_bpp_int_roundup(limits-
> >link.min_bpp_x16));
> 
>  	dsc_src_max_bpp = dsc_src_max_compressed_bpp(intel_dp);
> -	dsc_sink_max_bpp = dsc_sink_max_compressed_bpp(connector,
> pipe_config, pipe_bpp / 3);
> +	dsc_sink_max_bpp =
> intel_dp_dsc_sink_max_compressed_bpp(connector,
> +								pipe_config,
> +								pipe_bpp / 3);
>  	dsc_max_bpp = dsc_sink_max_bpp ? min(dsc_sink_max_bpp,
> dsc_src_max_bpp) : dsc_src_max_bpp;
> 
>  	dsc_joiner_max_bpp = get_max_compressed_bpp_with_joiner(i915,
> adjusted_mode->clock, @@ -2104,12 +2106,14 @@ static int
> intel_edp_dsc_compute_pipe_bpp(struct intel_dp *intel_dp,
>  	pipe_config->lane_count = limits->max_lane_count;
> 
>  	dsc_src_min_bpp = dsc_src_min_compressed_bpp();
> -	dsc_sink_min_bpp = dsc_sink_min_compressed_bpp(pipe_config);
> +	dsc_sink_min_bpp =
> intel_dp_dsc_sink_min_compressed_bpp(pipe_config);
>  	dsc_min_bpp = max(dsc_src_min_bpp, dsc_sink_min_bpp);
>  	dsc_min_bpp = max(dsc_min_bpp, to_bpp_int_roundup(limits-
> >link.min_bpp_x16));
> 
>  	dsc_src_max_bpp = dsc_src_max_compressed_bpp(intel_dp);
> -	dsc_sink_max_bpp = dsc_sink_max_compressed_bpp(connector,
> pipe_config, pipe_bpp / 3);
> +	dsc_sink_max_bpp =
> intel_dp_dsc_sink_max_compressed_bpp(connector,
> +								pipe_config,
> +								pipe_bpp / 3);
>  	dsc_max_bpp = dsc_sink_max_bpp ? min(dsc_sink_max_bpp,
> dsc_src_max_bpp) : dsc_src_max_bpp;
>  	dsc_max_bpp = min(dsc_max_bpp, to_bpp_int(limits-
> >link.max_bpp_x16));
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.h
> b/drivers/gpu/drm/i915/display/intel_dp.h
> index 75ffab92bba41..af535b3f03ae9 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.h
> +++ b/drivers/gpu/drm/i915/display/intel_dp.h
> @@ -126,6 +126,10 @@ u16 intel_dp_dsc_get_max_compressed_bpp(struct
> drm_i915_private *i915,
>  					enum intel_output_format
> output_format,
>  					u32 pipe_bpp,
>  					u32 timeslots);
> +int intel_dp_dsc_sink_min_compressed_bpp(struct intel_crtc_state
> +*pipe_config); int intel_dp_dsc_sink_max_compressed_bpp(const struct
> intel_connector *connector,
> +					 struct intel_crtc_state *pipe_config,
> +					 int bpc);
>  u8 intel_dp_dsc_get_slice_count(const struct intel_connector *connector,
>  				int mode_clock, int mode_hdisplay,
>  				bool bigjoiner);
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> index d6c52906ac6c3..457ace825d931 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -157,6 +157,9 @@ static int intel_dp_mst_find_vcpi_slots_for_bpp(struct
> intel_encoder *encoder,
>  						      crtc_state->port_clock,
>  						      crtc_state->lane_count);
> 
> +	drm_dbg_kms(&i915->drm, "Looking for slots in range min bpp %d max
> bpp %d\n",
> +		    min_bpp, max_bpp);
> +
>  	for (bpp = max_bpp; bpp >= min_bpp; bpp -= step) {
>  		struct intel_link_m_n remote_m_n;
>  		int link_bpp;
> @@ -246,8 +249,7 @@ static int intel_dp_dsc_mst_compute_link_config(struct
> intel_encoder *encoder,
>  	u8 dsc_bpc[3] = {};
>  	int min_bpp, max_bpp, sink_min_bpp, sink_max_bpp;
>  	u8 dsc_max_bpc;
> -	bool need_timeslot_recalc = false;
> -	u32 last_compressed_bpp;
> +	int min_compressed_bpp, max_compressed_bpp;
> 
>  	/* Max DSC Input BPC for ICL is 10 and for TGL+ is 12 */
>  	if (DISPLAY_VER(i915) >= 12)
> @@ -283,38 +285,32 @@ static int
> intel_dp_dsc_mst_compute_link_config(struct intel_encoder *encoder,
>  	if (max_bpp > sink_max_bpp)
>  		max_bpp = sink_max_bpp;
> 
> -	min_bpp = max(min_bpp, to_bpp_int_roundup(limits-
> >link.min_bpp_x16));
> -	max_bpp = min(max_bpp, to_bpp_int(limits->link.max_bpp_x16));
> +	max_compressed_bpp =
> intel_dp_dsc_sink_max_compressed_bpp(connector,
> +								  crtc_state,
> +								  max_bpp /
> 3);
> +	max_compressed_bpp = min(max_compressed_bpp,
> +				 to_bpp_int(limits->link.max_bpp_x16));
> 
> -	slots = intel_dp_mst_find_vcpi_slots_for_bpp(encoder, crtc_state,
> max_bpp,
> -						     min_bpp, limits,
> -						     conn_state, 2 * 3, true);
> +	min_compressed_bpp =
> intel_dp_dsc_sink_min_compressed_bpp(crtc_state);
> +	min_compressed_bpp = max(min_compressed_bpp,
> +				 to_bpp_int_roundup(limits-
> >link.min_bpp_x16));
> +
> +	drm_dbg_kms(&i915->drm, "DSC Sink supported compressed min bpp
> %d compressed max bpp %d\n",
> +		    min_compressed_bpp, max_compressed_bpp);
> +
> +	/* Align compressed bpps according to our own constraints */
> +	max_compressed_bpp = intel_dp_dsc_nearest_valid_bpp(i915,
> max_compressed_bpp,
> +							    crtc_state-
> >pipe_bpp);
> +	min_compressed_bpp = intel_dp_dsc_nearest_valid_bpp(i915,
> min_compressed_bpp,
> +							    crtc_state-
> >pipe_bpp);
> +
> +	slots = intel_dp_mst_find_vcpi_slots_for_bpp(encoder, crtc_state,
> max_compressed_bpp,
> +						     min_compressed_bpp,
> limits,
> +						     conn_state, 1, true);
> 
>  	if (slots < 0)
>  		return slots;
> 
> -	last_compressed_bpp = crtc_state->dsc.compressed_bpp;
> -
> -	crtc_state->dsc.compressed_bpp =
> intel_dp_dsc_nearest_valid_bpp(i915,
> -
> 	last_compressed_bpp,
> -
> 	crtc_state->pipe_bpp);
> -
> -	if (crtc_state->dsc.compressed_bpp != last_compressed_bpp)
> -		need_timeslot_recalc = true;
> -
> -	/*
> -	 * Apparently some MST hubs dislike if vcpi slots are not matching
> precisely
> -	 * the actual compressed bpp we use.
> -	 */
> -	if (need_timeslot_recalc) {
> -		slots = intel_dp_mst_find_vcpi_slots_for_bpp(encoder,
> crtc_state,
> -							     crtc_state-
> >dsc.compressed_bpp,
> -							     crtc_state-
> >dsc.compressed_bpp,
> -							     limits, conn_state,
> 2 * 3, true);
> -		if (slots < 0)
> -			return slots;
> -	}
> -
>  	return 0;
>  }
>  static int intel_dp_mst_update_slots(struct intel_encoder *encoder,
> --
> 2.39.2





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