drm/display/dp: Add helper function to get DSC bpp precision

Add helper to get the DSC bits_per_pixel precision for the DP sink.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Sui Jingfeng <suijingfeng@loongson.cn>
Acked-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20231110101020.4067342-2-ankit.k.nautiyal@intel.com

drivers/gpu/drm/display/drm_dp_helper.c

@@ -2325,6 +2325,33 @@ int drm_dp_read_desc(struct drm_dp_aux *aux, struct drm_dp_desc *desc,
 }
 EXPORT_SYMBOL(drm_dp_read_desc);
 
+/**
+ * drm_dp_dsc_sink_bpp_incr() - Get bits per pixel increment
+ * @dsc_dpcd: DSC capabilities from DPCD
+ *
+ * Returns the bpp precision supported by the DP sink.
+ */
+u8 drm_dp_dsc_sink_bpp_incr(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE])
+{
+	u8 bpp_increment_dpcd = dsc_dpcd[DP_DSC_BITS_PER_PIXEL_INC - DP_DSC_SUPPORT];
+
+	switch (bpp_increment_dpcd) {
+	case DP_DSC_BITS_PER_PIXEL_1_16:
+		return 16;
+	case DP_DSC_BITS_PER_PIXEL_1_8:
+		return 8;
+	case DP_DSC_BITS_PER_PIXEL_1_4:
+		return 4;
+	case DP_DSC_BITS_PER_PIXEL_1_2:
+		return 2;
+	case DP_DSC_BITS_PER_PIXEL_1_1:
+		return 1;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_dp_dsc_sink_bpp_incr);
+
 /**
  * drm_dp_dsc_sink_max_slice_count() - Get the max slice count
  * supported by the DSC sink.

include/drm/display/drm_dp_helper.h

@@ -164,6 +164,7 @@ drm_dp_is_branch(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
 }
 
 /* DP/eDP DSC support */
+u8 drm_dp_dsc_sink_bpp_incr(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE]);
 u8 drm_dp_dsc_sink_max_slice_count(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE],
 				   bool is_edp);
 u8 drm_dp_dsc_sink_line_buf_depth(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE]);