[Intel-gfx] [PATCH v2] drm/i915/dp: Increase slice_height for DP

[Suraj Kandpal]

According VDSC spec 1.2a Section 3.8 Options for Slice
implies that 108 lines is an optimal slice height, but any
size can be used as long as vertical active
integer multiple and maximum vertical slice count requirements are met.

Bspec: 49259

Cc: Jani Nikula <jani.nikula at linux.intel.com>
Cc: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
Cc: Swati Sharma <swati2.sharma at intel.com>
Signed-off-by: Suraj Kandpal <suraj.kandpal at intel.com>

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 62cbab7402e9..cb4fbcd935db 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -1415,6 +1415,30 @@ static int intel_dp_sink_dsc_version_minor(struct intel_dp *intel_dp)
 		DP_DSC_MINOR_SHIFT;
 }
 
+static int intel_dp_get_slice_height(int vactive)
+{
+	int slice_height;
+
+	/*
+	 * VDSC1.2a spec in Section 3.8 Options for Slices implies that
+	 * 108 lines is an optimal slice height,
+	 * but any size can be used as long as vertical active integer
+	 * multiple and maximum vertical slice count requirements are met.
+	 */
+	for (slice_height = 108; slice_height <= vactive; slice_height += 2)
+		if (vactive % slice_height == 0)
+			return slice_height;
+
+	if (vactive % 8 == 0)
+		slice_height = 8;
+	else if (vactive % 4 == 0)
+		slice_height = 4;
+	else
+		slice_height = 2;
+
+	return slice_height;
+}
+
 static int intel_dp_dsc_compute_params(struct intel_encoder *encoder,
 				       struct intel_crtc_state *crtc_state)
 {
@@ -1433,17 +1457,7 @@ static int intel_dp_dsc_compute_params(struct intel_encoder *encoder,
 	vdsc_cfg->rc_model_size = DSC_RC_MODEL_SIZE_CONST;
 	vdsc_cfg->pic_height = crtc_state->hw.adjusted_mode.crtc_vdisplay;
 
-	/*
-	 * Slice Height of 8 works for all currently available panels. So start
-	 * with that if pic_height is an integral multiple of 8. Eventually add
-	 * logic to try multiple slice heights.
-	 */
-	if (vdsc_cfg->pic_height % 8 == 0)
-		vdsc_cfg->slice_height = 8;
-	else if (vdsc_cfg->pic_height % 4 == 0)
-		vdsc_cfg->slice_height = 4;
-	else
-		vdsc_cfg->slice_height = 2;
+	vdsc_cfg->slice_height = intel_dp_get_slice_height(vdsc_cfg->pic_height);
 
 	ret = intel_dsc_compute_params(crtc_state);
 	if (ret)
-- 
2.25.1