RE: [PATCH 09/11] drm/i915/dp_mst: Use precision of 1/16 for computing bpp

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> -----Original Message-----
> From: Nautiyal, Ankit K <ankit.k.nautiyal@xxxxxxxxx>
> Sent: Friday, November 10, 2023 3:40 PM
> To: dri-devel@xxxxxxxxxxxxxxxxxxxxx; intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> Cc: Sharma, Swati2 <swati2.sharma@xxxxxxxxx>; Kulkarni, Vandita
> <vandita.kulkarni@xxxxxxxxx>; Kandpal, Suraj <suraj.kandpal@xxxxxxxxx>;
> suijingfeng@xxxxxxxxxxx
> Subject: [PATCH 09/11] drm/i915/dp_mst: Use precision of 1/16 for computing
> bpp
> 
> Modify the functions to deal with bpps with 1/16 precision.
> This will make way for cases when DSC with fractional bpp is used.
> For bpp without DSC, there is no change, as we still use whole numbers.
> 

LGTM.

Reviewed-by: Suraj Kandpal <suraj.kandpal@xxxxxxxxx>

> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@xxxxxxxxx>
> ---
>  drivers/gpu/drm/i915/display/intel_dp_mst.c | 56 +++++++++++----------
>  1 file changed, 30 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> index 5c7e9d296483..e7806fe11b9d 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -47,20 +47,21 @@
>  #include "intel_vdsc.h"
>  #include "skl_scaler.h"
> 
> -static int intel_dp_mst_check_constraints(struct drm_i915_private *i915, int
> bpp,
> +static int intel_dp_mst_check_constraints(struct drm_i915_private
> +*i915, int bpp_x16,
>  					  const struct drm_display_mode
> *adjusted_mode,
>  					  struct intel_crtc_state *crtc_state,
>  					  bool dsc)
>  {
>  	if (intel_dp_is_uhbr(crtc_state) && DISPLAY_VER(i915) <= 13 && dsc) {
> -		int output_bpp = bpp;
> +		int output_bpp_x16 = bpp_x16;
>  		/* DisplayPort 2 128b/132b, bits per lane is always 32 */
>  		int symbol_clock = crtc_state->port_clock / 32;
> 
> -		if (output_bpp * adjusted_mode->crtc_clock >=
> +		if (DIV_ROUND_UP(output_bpp_x16 * adjusted_mode-
> >crtc_clock, 16) >=
>  		    symbol_clock * 72) {
>  			drm_dbg_kms(&i915->drm, "UHBR check
> failed(required bw %d available %d)\n",
> -				    output_bpp * adjusted_mode->crtc_clock,
> symbol_clock * 72);
> +				    DIV_ROUND_UP(output_bpp_x16 *
> adjusted_mode->crtc_clock, 16),
> +				    symbol_clock * 72);
>  			return -EINVAL;
>  		}
>  	}
> @@ -127,8 +128,8 @@ static void intel_dp_mst_compute_m_n(const struct
> intel_crtc_state *crtc_state,
> 
>  static int intel_dp_mst_find_vcpi_slots_for_bpp(struct intel_encoder
> *encoder,
>  						struct intel_crtc_state
> *crtc_state,
> -						int max_bpp,
> -						int min_bpp,
> +						int max_bpp_x16,
> +						int min_bpp_x16,
>  						struct link_config_limits
> *limits,
>  						struct drm_connector_state
> *conn_state,
>  						int step,
> @@ -143,7 +144,7 @@ static int intel_dp_mst_find_vcpi_slots_for_bpp(struct
> intel_encoder *encoder,
>  	struct drm_i915_private *i915 = to_i915(connector->base.dev);
>  	const struct drm_display_mode *adjusted_mode =
>  		&crtc_state->hw.adjusted_mode;
> -	int bpp, slots = -EINVAL;
> +	int bpp_x16, slots = -EINVAL;
>  	int ret = 0;
> 
>  	mst_state = drm_atomic_get_mst_topology_state(state, &intel_dp-
> >mst_mgr); @@ -164,25 +165,25 @@ 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);
> +	drm_dbg_kms(&i915->drm, "Looking for slots in range min bpp "
> BPP_X16_FMT " max bpp " BPP_X16_FMT "\n",
> +		    BPP_X16_ARGS(min_bpp_x16),
> BPP_X16_ARGS(max_bpp_x16));
> 
> -	for (bpp = max_bpp; bpp >= min_bpp; bpp -= step) {
> +	for (bpp_x16 = max_bpp_x16; bpp_x16 >= min_bpp_x16; bpp_x16 -=
> step) {
>  		struct intel_link_m_n remote_m_n;
> -		int link_bpp;
> +		int link_bpp_x16;
> 
> -		drm_dbg_kms(&i915->drm, "Trying bpp %d\n", bpp);
> +		drm_dbg_kms(&i915->drm, "Trying bpp " BPP_X16_FMT "\n",
> +BPP_X16_ARGS(bpp_x16));
> 
> -		ret = intel_dp_mst_check_constraints(i915, bpp,
> adjusted_mode, crtc_state, dsc);
> +		ret = intel_dp_mst_check_constraints(i915, bpp_x16,
> adjusted_mode,
> +crtc_state, dsc);
>  		if (ret)
>  			continue;
> 
> -		link_bpp = dsc ? bpp :
> -			intel_dp_output_bpp(crtc_state->output_format,
> bpp);
> +		link_bpp_x16 = dsc ? bpp_x16 :
> +			intel_dp_output_bpp(crtc_state->output_format,
> to_bpp_int(bpp_x16));
> 
> -		intel_dp_mst_compute_m_n(crtc_state, connector, false, dsc,
> to_bpp_x16(link_bpp),
> +		intel_dp_mst_compute_m_n(crtc_state, connector, false, dsc,
> +link_bpp_x16,
>  					 &crtc_state->dp_m_n);
> -		intel_dp_mst_compute_m_n(crtc_state, connector, true, dsc,
> to_bpp_x16(link_bpp),
> +		intel_dp_mst_compute_m_n(crtc_state, connector, true, dsc,
> +link_bpp_x16,
>  					 &remote_m_n);
> 
>  		/*
> @@ -225,10 +226,11 @@ static int
> intel_dp_mst_find_vcpi_slots_for_bpp(struct intel_encoder *encoder,
>  			    slots);
>  	} else {
>  		if (!dsc)
> -			crtc_state->pipe_bpp = bpp;
> +			crtc_state->pipe_bpp = to_bpp_int(bpp_x16);
>  		else
> -			crtc_state->dsc.compressed_bpp_x16 =
> to_bpp_x16(bpp);
> -		drm_dbg_kms(&i915->drm, "Got %d slots for pipe bpp %d dsc
> %d\n", slots, bpp, dsc);
> +			crtc_state->dsc.compressed_bpp_x16 = bpp_x16;
> +		drm_dbg_kms(&i915->drm, "Got %d slots for pipe bpp "
> BPP_X16_FMT " dsc %d\n",
> +			    slots, BPP_X16_ARGS(bpp_x16), dsc);
>  	}
> 
>  	return slots;
> @@ -246,10 +248,10 @@ static int intel_dp_mst_compute_link_config(struct
> intel_encoder *encoder,
>  	 * YUV420 is only half of the pipe bpp value.
>  	 */
>  	slots = intel_dp_mst_find_vcpi_slots_for_bpp(encoder, crtc_state,
> -						     to_bpp_int(limits-
> >link.max_bpp_x16),
> -						     to_bpp_int(limits-
> >link.min_bpp_x16),
> +						     limits->link.max_bpp_x16,
> +						     limits->link.min_bpp_x16,
>  						     limits,
> -						     conn_state, 2 * 3, false);
> +						     conn_state, 2 * 3 * 16,
> false);
> 
>  	if (slots < 0)
>  		return slots;
> @@ -325,9 +327,11 @@ static int
> intel_dp_dsc_mst_compute_link_config(struct intel_encoder *encoder,
>  	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);
> +	slots = intel_dp_mst_find_vcpi_slots_for_bpp(encoder, crtc_state,
> +
> to_bpp_x16(max_compressed_bpp),
> +
> to_bpp_x16(min_compressed_bpp),
> +						     limits,
> +						     conn_state, 16, true);
> 
>  	if (slots < 0)
>  		return slots;
> --
> 2.40.1





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