Commit 00f00859 authored by Imre Deak's avatar Imre Deak
Browse files

drm/i915/dp_mst: Add support for fractional compressed link bpps on MST 



Add support for a fractional compressed link bpp on an MST link. Leave
the actual enabling of fractional bpps to a follow-up change.

While at it add an assert before the bpp loop, that the min and max bpps
are aligned to the bpp step. This should hold regardless of the non-DSC/DSC
or MST/UHBR-SST modes.

This keeps the mode validation and DSC->DPT BW specific maximum link
bpps as rounded-down integer values still, changing those to a
fractional value is left for later, add here TODO comments for them.

v2:
- Align the min/max bpp value to the bpp step.
- Assert that the min/max bpp values are aligned to the bpp step.

Reviewed-by: default avatarAnkit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: default avatarImre Deak <imre.deak@intel.com>
Link: https://lore.kernel.org/r/20250509180340.554867-9-imre.deak@intel.com
parent 7acc7a6f

drivers/gpu/drm/i915/display/intel_dp.c

+1 −0
Original line number Diff line number Diff line
@@ -958,6 +958,7 @@ u32 get_max_compressed_bpp_with_joiner(struct intel_display *display, 
	return max_bpp;

}



/* TODO: return a bpp_x16 value */

u16 intel_dp_dsc_get_max_compressed_bpp(struct intel_display *display,

					u32 link_clock, u32 lane_count,

					u32 mode_clock, u32 mode_hdisplay,

drivers/gpu/drm/i915/display/intel_dp_mst.c

+23 −9
Original line number Diff line number Diff line
@@ -23,6 +23,9 @@ 
 *

 */



#include <linux/log2.h>

#include <linux/math.h>



#include <drm/drm_atomic.h>

#include <drm/drm_atomic_helper.h>

#include <drm/drm_edid.h>
@@ -135,6 +138,7 @@ static bool intel_dp_mst_inc_active_streams(struct intel_dp *intel_dp) 
	return intel_dp->mst.active_streams++ == 0;

}



/* TODO: return a bpp_x16 value */

static int intel_dp_mst_max_dpt_bpp(const struct intel_crtc_state *crtc_state,

				    bool dsc)

{
@@ -315,6 +319,8 @@ int intel_dp_mtp_tu_compute_config(struct intel_dp *intel_dp, 
		}

	}



	drm_WARN_ON(display->drm, min_bpp_x16 % bpp_step_x16 || max_bpp_x16 % bpp_step_x16);



	for (bpp_x16 = max_bpp_x16; bpp_x16 >= min_bpp_x16; bpp_x16 -= bpp_step_x16) {

		int local_bw_overhead;

		int link_bpp_x16;
@@ -460,7 +466,8 @@ static int mst_stream_dsc_compute_link_config(struct intel_dp *intel_dp, 
	int num_bpc;

	u8 dsc_bpc[3] = {};

	int min_bpp, max_bpp, sink_min_bpp, sink_max_bpp;

	int min_compressed_bpp, max_compressed_bpp;

	int min_compressed_bpp_x16, max_compressed_bpp_x16;

	int bpp_step_x16;



	max_bpp = limits->pipe.max_bpp;

	min_bpp = limits->pipe.min_bpp;
@@ -485,21 +492,28 @@ static int mst_stream_dsc_compute_link_config(struct intel_dp *intel_dp, 


	crtc_state->pipe_bpp = max_bpp;



	max_compressed_bpp = fxp_q4_to_int(limits->link.max_bpp_x16);

	min_compressed_bpp = fxp_q4_to_int_roundup(limits->link.min_bpp_x16);

	min_compressed_bpp_x16 = limits->link.min_bpp_x16;

	max_compressed_bpp_x16 = limits->link.max_bpp_x16;



	drm_dbg_kms(display->drm,

		    "DSC Sink supported compressed min bpp " FXP_Q4_FMT " compressed max bpp " FXP_Q4_FMT "\n",

		    FXP_Q4_ARGS(min_compressed_bpp_x16), FXP_Q4_ARGS(max_compressed_bpp_x16));



	bpp_step_x16 = fxp_q4_from_int(1);



	drm_dbg_kms(display->drm, "DSC Sink supported compressed min bpp %d compressed max bpp %d\n",

		    min_compressed_bpp, max_compressed_bpp);

	max_compressed_bpp_x16 = min(max_compressed_bpp_x16, fxp_q4_from_int(crtc_state->pipe_bpp) - bpp_step_x16);



	max_compressed_bpp = min(max_compressed_bpp, crtc_state->pipe_bpp - 1);

	drm_WARN_ON(display->drm, !is_power_of_2(bpp_step_x16));

	min_compressed_bpp_x16 = round_up(min_compressed_bpp_x16, bpp_step_x16);

	max_compressed_bpp_x16 = round_down(max_compressed_bpp_x16, bpp_step_x16);



	crtc_state->lane_count = limits->max_lane_count;

	crtc_state->port_clock = limits->max_rate;



	return intel_dp_mtp_tu_compute_config(intel_dp, crtc_state, conn_state,

					      fxp_q4_from_int(min_compressed_bpp),

					      fxp_q4_from_int(max_compressed_bpp),

					      fxp_q4_from_int(1), true);

					      min_compressed_bpp_x16,

					      max_compressed_bpp_x16,

					      bpp_step_x16, true);

}



static int mode_hblank_period_ns(const struct drm_display_mode *mode)