drm/i915/dsc: move rc_buf_thresh values to common helper

The rc_buf_thresh values are common to all DSC implementations. Move
them to the common helper together with the code to propagate them to
the drm_dsc_config.

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Marijn Suijten <marijn.suijten@somainline.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230517102807.2181589-3-dmitry.baryshkov@linaro.org
Acked-by: Dave Airlie <airlied@redhat.com>

3 files changed, 37 insertions, 23 deletions

diff --git a/drivers/gpu/drm/display/drm_dsc_helper.c b/drivers/gpu/drm/display/drm_dsc_helper.c
index c869c6e51e2b..be91abe2cfb2 100644
--- a/drivers/gpu/drm/display/drm_dsc_helper.c
+++ b/drivers/gpu/drm/display/drm_dsc_helper.c
@@ -270,6 +270,41 @@ void drm_dsc_pps_payload_pack(struct drm_dsc_picture_parameter_set *pps_payload,
 }
 EXPORT_SYMBOL(drm_dsc_pps_payload_pack);
 
+/* From DSC_v1.11 spec, rc_parameter_Set syntax element typically constant */
+static const u16 drm_dsc_rc_buf_thresh[] = {
+	896, 1792, 2688, 3584, 4480, 5376, 6272, 6720, 7168, 7616,
+	7744, 7872, 8000, 8064
+};
+
+/**
+ * drm_dsc_set_rc_buf_thresh() - Set thresholds for the RC model
+ * in accordance with the DSC 1.2 specification.
+ *
+ * @vdsc_cfg: DSC Configuration data partially filled by driver
+ */
+void drm_dsc_set_rc_buf_thresh(struct drm_dsc_config *vdsc_cfg)
+{
+	int i;
+
+	BUILD_BUG_ON(ARRAY_SIZE(drm_dsc_rc_buf_thresh) !=
+		     DSC_NUM_BUF_RANGES - 1);
+	BUILD_BUG_ON(ARRAY_SIZE(drm_dsc_rc_buf_thresh) !=
+		     ARRAY_SIZE(vdsc_cfg->rc_buf_thresh));
+
+	for (i = 0; i < ARRAY_SIZE(drm_dsc_rc_buf_thresh); i++)
+		vdsc_cfg->rc_buf_thresh[i] = drm_dsc_rc_buf_thresh[i] >> 6;
+
+	/*
+	 * For 6bpp, RC Buffer threshold 12 and 13 need a different value
+	 * as per C Model
+	 */
+	if (vdsc_cfg->bits_per_pixel == 6 << 4) {
+		vdsc_cfg->rc_buf_thresh[12] = 7936 >> 6;
+		vdsc_cfg->rc_buf_thresh[13] = 8000 >> 6;
+	}
+}
+EXPORT_SYMBOL(drm_dsc_set_rc_buf_thresh);
+
 /**
  * drm_dsc_compute_rc_parameters() - Write rate control
  * parameters to the dsc configuration defined in
diff --git a/drivers/gpu/drm/i915/display/intel_vdsc.c b/drivers/gpu/drm/i915/display/intel_vdsc.c
index 7003ae9f683a..2fd08375bbe3 100644
--- a/drivers/gpu/drm/i915/display/intel_vdsc.c
+++ b/drivers/gpu/drm/i915/display/intel_vdsc.c
@@ -37,12 +37,6 @@ enum COLUMN_INDEX_BPC {
 	MAX_COLUMN_INDEX
 };
 
-/* From DSC_v1.11 spec, rc_parameter_Set syntax element typically constant */
-static const u16 rc_buf_thresh[] = {
-	896, 1792, 2688, 3584, 4480, 5376, 6272, 6720, 7168, 7616,
-	7744, 7872, 8000, 8064
-};
-
 struct rc_parameters {
 	u16 initial_xmit_delay;
 	u8 first_line_bpg_offset;
@@ -543,23 +537,7 @@ int intel_dsc_compute_params(struct intel_crtc_state *pipe_config)
 
 	vdsc_cfg->bits_per_component = pipe_config->pipe_bpp / 3;
 
-	for (i = 0; i < DSC_NUM_BUF_RANGES - 1; i++) {
-		/*
-		 * six 0s are appended to the lsb of each threshold value
-		 * internally in h/w.
-		 * Only 8 bits are allowed for programming RcBufThreshold
-		 */
-		vdsc_cfg->rc_buf_thresh[i] = rc_buf_thresh[i] >> 6;
-	}
-
-	/*
-	 * For 6bpp, RC Buffer threshold 12 and 13 need a different value
-	 * as per C Model
-	 */
-	if (compressed_bpp == 6) {
-		vdsc_cfg->rc_buf_thresh[12] = 0x7C;
-		vdsc_cfg->rc_buf_thresh[13] = 0x7D;
-	}
+	drm_dsc_set_rc_buf_thresh(vdsc_cfg);
 
 	/*
 	 * From XE_LPD onwards we supports compression bpps in steps of 1
diff --git a/include/drm/display/drm_dsc_helper.h b/include/drm/display/drm_dsc_helper.h
index 8b41edbbabab..706ba1d34742 100644
--- a/include/drm/display/drm_dsc_helper.h
+++ b/include/drm/display/drm_dsc_helper.h
@@ -14,6 +14,7 @@ void drm_dsc_dp_pps_header_init(struct dp_sdp_header *pps_header);
 int drm_dsc_dp_rc_buffer_size(u8 rc_buffer_block_size, u8 rc_buffer_size);
 void drm_dsc_pps_payload_pack(struct drm_dsc_picture_parameter_set *pps_sdp,
 			      const struct drm_dsc_config *dsc_cfg);
+void drm_dsc_set_rc_buf_thresh(struct drm_dsc_config *vdsc_cfg);
 int drm_dsc_compute_rc_parameters(struct drm_dsc_config *vdsc_cfg);
 
 #endif /* _DRM_DSC_HELPER_H_ */