drm/display/dsc: add helper to set semi-const parameters

Add a helper setting config values which are typically constant across
operating modes (table E-4 of the standard) and mux_word_size (which is
a const according to 3.5.2).

Signed-off-by: Dmitry Baryshkov <[e-mail]>
Reviewed-by: Marijn Suijten <[e-mail]>
Signed-off-by: Jessica Zhang <[e-mail]>
Patchwork: https://patchwork.freedesktop.org/patch/539280/
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Dmitry Baryshkov <[e-mail]>

drivers/gpu/drm/display/drm_dsc_helper.c

···
 }
 EXPORT_SYMBOL(drm_dsc_pps_payload_pack);
 
+/**
+ * drm_dsc_set_const_params() - Set DSC parameters considered typically
+ * constant across operation modes
+ *
+ * @vdsc_cfg:
+ * DSC Configuration data partially filled by driver
+ */
+void drm_dsc_set_const_params(struct drm_dsc_config *vdsc_cfg)
+{
+	if (!vdsc_cfg->rc_model_size)
+		vdsc_cfg->rc_model_size = DSC_RC_MODEL_SIZE_CONST;
+	vdsc_cfg->rc_edge_factor = DSC_RC_EDGE_FACTOR_CONST;
+	vdsc_cfg->rc_tgt_offset_high = DSC_RC_TGT_OFFSET_HI_CONST;
+	vdsc_cfg->rc_tgt_offset_low = DSC_RC_TGT_OFFSET_LO_CONST;
+
+	if (vdsc_cfg->bits_per_component <= 10)
+		vdsc_cfg->mux_word_size = DSC_MUX_WORD_SIZE_8_10_BPC;
+	else
+		vdsc_cfg->mux_word_size = DSC_MUX_WORD_SIZE_12_BPC;
+}
+EXPORT_SYMBOL(drm_dsc_set_const_params);
+
 /* 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,

include/drm/display/drm_dsc_helper.h

···
 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_const_params(struct drm_dsc_config *vdsc_cfg);
 void drm_dsc_set_rc_buf_thresh(struct drm_dsc_config *vdsc_cfg);
 int drm_dsc_setup_rc_params(struct drm_dsc_config *vdsc_cfg, enum drm_dsc_params_type type);
 int drm_dsc_compute_rc_parameters(struct drm_dsc_config *vdsc_cfg);