drm/dp: DRM DP helper/macros to get DP sink DSC parameters

This patch adds inline functions and helpers for obtaining
DP sink's supported DSC parameters like DSC sink support,
eDP compressed BPP supported, maximum slice count supported
by the sink devices, DSC line buffer bit depth supported on DP sink,
DSC sink maximum color depth by parsing corresponding DPCD registers.

v4:
* Add helper to give line buf bit depth (Manasi)
* Correct the bit masking in color depth helper (manasi)
v3:
* Use SLICE_CAP_2 for DP (Anusha)
v2:
* Add DSC sink support macro (Jani N)

Cc: Gaurav K Singh <gaurav.k.singh@intel.com>
Cc: dri-devel@lists.freedesktop.org
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Reviewed-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Reviewed-by: Gaurav K Singh <gaurav.k.singh@intel.com>
Acked-by: Sean Paul <seanpaul@chromium.org> (For merging through
drm-intel)
Link: https://patchwork.freedesktop.org/patch/msgid/20181031001923.31442-4-manasi.d.navare@intel.com

drivers/gpu/drm/drm_dp_helper.c

@@ -1352,3 +1352,93 @@ int drm_dp_read_desc(struct drm_dp_aux *aux, struct drm_dp_desc *desc,
 	return 0;
 }
 EXPORT_SYMBOL(drm_dp_read_desc);
+
+/**
+ * DRM DP Helpers for DSC
+ */
+u8 drm_dp_dsc_sink_max_slice_count(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE],
+				   bool is_edp)
+{
+	u8 slice_cap1 = dsc_dpcd[DP_DSC_SLICE_CAP_1 - DP_DSC_SUPPORT];
+
+	if (is_edp) {
+		/* For eDP, register DSC_SLICE_CAPABILITIES_1 gives slice count */
+		if (slice_cap1 & DP_DSC_4_PER_DP_DSC_SINK)
+			return 4;
+		if (slice_cap1 & DP_DSC_2_PER_DP_DSC_SINK)
+			return 2;
+		if (slice_cap1 & DP_DSC_1_PER_DP_DSC_SINK)
+			return 1;
+	} else {
+		/* For DP, use values from DSC_SLICE_CAP_1 and DSC_SLICE_CAP2 */
+		u8 slice_cap2 = dsc_dpcd[DP_DSC_SLICE_CAP_2 - DP_DSC_SUPPORT];
+
+		if (slice_cap2 & DP_DSC_24_PER_DP_DSC_SINK)
+			return 24;
+		if (slice_cap2 & DP_DSC_20_PER_DP_DSC_SINK)
+			return 20;
+		if (slice_cap2 & DP_DSC_16_PER_DP_DSC_SINK)
+			return 16;
+		if (slice_cap1 & DP_DSC_12_PER_DP_DSC_SINK)
+			return 12;
+		if (slice_cap1 & DP_DSC_10_PER_DP_DSC_SINK)
+			return 10;
+		if (slice_cap1 & DP_DSC_8_PER_DP_DSC_SINK)
+			return 8;
+		if (slice_cap1 & DP_DSC_6_PER_DP_DSC_SINK)
+			return 6;
+		if (slice_cap1 & DP_DSC_4_PER_DP_DSC_SINK)
+			return 4;
+		if (slice_cap1 & DP_DSC_2_PER_DP_DSC_SINK)
+			return 2;
+		if (slice_cap1 & DP_DSC_1_PER_DP_DSC_SINK)
+			return 1;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_dp_dsc_sink_max_slice_count);
+
+u8 drm_dp_dsc_sink_line_buf_depth(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE])
+{
+	u8 line_buf_depth = dsc_dpcd[DP_DSC_LINE_BUF_BIT_DEPTH - DP_DSC_SUPPORT];
+
+	switch (line_buf_depth & DP_DSC_LINE_BUF_BIT_DEPTH_MASK) {
+	case DP_DSC_LINE_BUF_BIT_DEPTH_9:
+		return 9;
+	case DP_DSC_LINE_BUF_BIT_DEPTH_10:
+		return 10;
+	case DP_DSC_LINE_BUF_BIT_DEPTH_11:
+		return 11;
+	case DP_DSC_LINE_BUF_BIT_DEPTH_12:
+		return 12;
+	case DP_DSC_LINE_BUF_BIT_DEPTH_13:
+		return 13;
+	case DP_DSC_LINE_BUF_BIT_DEPTH_14:
+		return 14;
+	case DP_DSC_LINE_BUF_BIT_DEPTH_15:
+		return 15;
+	case DP_DSC_LINE_BUF_BIT_DEPTH_16:
+		return 16;
+	case DP_DSC_LINE_BUF_BIT_DEPTH_8:
+		return 8;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_dp_dsc_sink_line_buf_depth);
+
+u8 drm_dp_dsc_sink_max_color_depth(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE])
+{
+	u8 color_depth = dsc_dpcd[DP_DSC_DEC_COLOR_DEPTH_CAP - DP_DSC_SUPPORT];
+
+	if (color_depth & DP_DSC_12_BPC)
+		return 12;
+	if (color_depth & DP_DSC_10_BPC)
+		return 10;
+	if (color_depth & DP_DSC_8_BPC)
+		return 8;
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_dp_dsc_sink_max_color_depth);

include/drm/drm_dp_helper.h

@@ -1116,6 +1116,36 @@ drm_dp_is_branch(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
 	return dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_PRESENT;
 }
 
+/* DP/eDP DSC support */
+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]);
+u8 drm_dp_dsc_sink_max_color_depth(const u8 dsc_dpc[DP_DSC_RECEIVER_CAP_SIZE]);
+
+static inline bool
+drm_dp_sink_supports_dsc(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE])
+{
+	return dsc_dpcd[DP_DSC_SUPPORT - DP_DSC_SUPPORT] &
+		DP_DSC_DECOMPRESSION_IS_SUPPORTED;
+}
+
+static inline u16
+drm_edp_dsc_sink_output_bpp(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE])
+{
+	return dsc_dpcd[DP_DSC_MAX_BITS_PER_PIXEL_LOW - DP_DSC_SUPPORT] |
+		(dsc_dpcd[DP_DSC_MAX_BITS_PER_PIXEL_HI - DP_DSC_SUPPORT] &
+		 DP_DSC_MAX_BITS_PER_PIXEL_HI_MASK <<
+		 DP_DSC_MAX_BITS_PER_PIXEL_HI_SHIFT);
+}
+
+static inline u32
+drm_dp_dsc_sink_max_slice_width(const u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE])
+{
+	/* Max Slicewidth = Number of Pixels * 320 */
+	return dsc_dpcd[DP_DSC_MAX_SLICE_WIDTH - DP_DSC_SUPPORT] *
+		DP_DSC_SLICE_WIDTH_MULTIPLIER;
+}
+
 /*
  * DisplayPort AUX channel
  */