[PATCH v2 6/8] drm/i915/hdmi: Add helper to check if DSC chunksize fits the sink limits

Introduce the helper intel_hdmi_dsc_bpp_fits_chunk_bytes() to check
whether the chunksize computed for the given slice configuration is with
in the sink's max chunksize limits.

Signed-off-by: Ankit Nautiyal <[email protected]>
Reviewed-by: Suraj Kandpal <[email protected]>
---
 drivers/gpu/drm/i915/display/intel_hdmi.c | 25 ++++++++++++++++++++---
 drivers/gpu/drm/i915/display/intel_hdmi.h |  2 ++
 2 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c b/drivers/gpu/drm/i915/display/intel_hdmi.c
index ee6a559762c5..6ab62a9e941c 100644
--- a/drivers/gpu/drm/i915/display/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
@@ -3369,11 +3369,30 @@ intel_hdmi_dsc_get_min_max_bpp(enum intel_output_format output_format, u8 bpc,
 		*max_dsc_bpp = min(*max_dsc_bpp, 12);
 }
 
+/*
+ * intel_hdmi_dsc_bpp_fits_chunk_bytes - check if a given compressed bpp keeps
+ * the per-scanline chunk size within the sink's max_chunk_bytes limit.
+ *
+ * @bpp: compressed bits per pixel to test
+ * @num_slices: num of slices supported by the source and sink
+ * @slice_width: dsc slice width supported by the source and sink
+ * @hdmi_max_chunk_bytes: max bytes in a line of chunks supported by sink
+ *
+ * @return: true if the resulting chunk size fits the sink limit
+ */
+bool
+intel_hdmi_dsc_bpp_fits_chunk_bytes(int bpp, int num_slices, int slice_width,
+				    int hdmi_max_chunk_bytes)
+{
+	int target_bytes = DIV_ROUND_UP((num_slices * slice_width * bpp), 8);
+
+	return target_bytes <= hdmi_max_chunk_bytes;
+}
+
 static int
 get_dsc_compressed_bpp(int num_slices, int slice_width, int hdmi_max_chunk_bytes,
 		       int src_fractional_bpp, int min_dsc_bpp, int max_dsc_bpp)
 {
-	int target_bytes;
 	bool bpp_found = false;
 	int bpp_decrement_x16;
 	int bpp_target;
@@ -3408,8 +3427,8 @@ get_dsc_compressed_bpp(int num_slices, int slice_width, int hdmi_max_chunk_bytes
 		int bpp;
 
 		bpp = DIV_ROUND_UP(bpp_target_x16, 16);
-		target_bytes = DIV_ROUND_UP((num_slices * slice_width * bpp), 8);
-		if (target_bytes <= hdmi_max_chunk_bytes) {
+		if (intel_hdmi_dsc_bpp_fits_chunk_bytes(bpp, num_slices, slice_width,
+							hdmi_max_chunk_bytes)) {
 			bpp_found = true;
 			break;
 		}
diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.h b/drivers/gpu/drm/i915/display/intel_hdmi.h
index 3ab75ef4836e..db87656eb27f 100644
--- a/drivers/gpu/drm/i915/display/intel_hdmi.h
+++ b/drivers/gpu/drm/i915/display/intel_hdmi.h
@@ -59,6 +59,8 @@ int intel_hdmi_dsc_get_bpp(int src_fractional_bpp, int slice_width,
 			   int bpc, bool hdmi_all_bpp, int hdmi_max_chunk_bytes);
 void intel_hdmi_dsc_get_min_max_bpp(enum intel_output_format output_format, u8 bpc,
 				    bool hdmi_all_bpp, int *min_dsc_bpp, int *max_dsc_bpp);
+bool intel_hdmi_dsc_bpp_fits_chunk_bytes(int bpp, int num_slices, int slice_width,
+					 int hdmi_max_chunk_bytes);
 int intel_hdmi_dsc_get_num_slices(const struct drm_display_mode *mode,
 				  enum intel_output_format output_format,
 				  int src_max_slices, int src_max_slice_width,
-- 
2.50.1