[PATCH v2 12/12] drm/i915/dp_mst: Enable fractional link bpps on MST if the bpp is forced

[Imre Deak]

Enable using a fractional (compressed) link bpp on MST links, if this is
supported and the link bpp is forced. Fractional link bpps will be
enabled by default as a follow-up change after testing this
functionality within a set of commonly used MST monitors and docks/hubs
which support it.

Signed-off-by: Imre Deak <imre.deak at intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c     | 6 +++++-
 drivers/gpu/drm/i915/display/intel_dp.h     | 2 ++
 drivers/gpu/drm/i915/display/intel_dp_mst.c | 2 +-
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 047473e3f6e6a..bba0a9db17a3c 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -2102,7 +2102,7 @@ static int dsc_src_max_compressed_bpp(struct intel_dp *intel_dp)
 /*
  * Note: for pre-13 display you still need to check the validity of each step.
  */
-static int intel_dp_dsc_bpp_step_x16(const struct intel_connector *connector)
+int intel_dp_dsc_bpp_step_x16(const struct intel_connector *connector)
 {
 	struct intel_display *display = to_intel_display(connector);
 	u8 incr = drm_dp_dsc_sink_bpp_incr(connector->dp.dsc_dpcd);
@@ -2110,6 +2110,10 @@ static int intel_dp_dsc_bpp_step_x16(const struct intel_connector *connector)
 	if (DISPLAY_VER(display) < 14 || !incr)
 		return fxp_q4_from_int(1);
 
+	if (connector->mst.dp &&
+	    !connector->link.force_bpp_x16 && !connector->mst.dp->force_dsc_fractional_bpp_en)
+		return fxp_q4_from_int(1);
+
 	/* fxp q4 */
 	return fxp_q4_from_int(1) / incr;
 }
diff --git a/drivers/gpu/drm/i915/display/intel_dp.h b/drivers/gpu/drm/i915/display/intel_dp.h
index f883fc0b65c06..c5ab25ee1a015 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.h
+++ b/drivers/gpu/drm/i915/display/intel_dp.h
@@ -210,4 +210,6 @@ int intel_dp_dsc_max_src_input_bpc(struct intel_display *display);
 int intel_dp_dsc_min_src_input_bpc(void);
 int intel_dp_dsc_min_src_compressed_bpp(void);
 
+int intel_dp_dsc_bpp_step_x16(const struct intel_connector *connector);
+
 #endif /* __INTEL_DP_H__ */
diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
index a1203e5f570cb..4a5f920c11e2a 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
@@ -521,7 +521,7 @@ static int mst_stream_dsc_compute_link_config(struct intel_dp *intel_dp,
 		    "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);
+	bpp_step_x16 = intel_dp_dsc_bpp_step_x16(connector);
 
 	max_compressed_bpp_x16 = min(max_compressed_bpp_x16, fxp_q4_from_int(crtc_state->pipe_bpp) - bpp_step_x16);
 
-- 
2.44.2