X-Git-Url: http://git.ipfire.org/?a=blobdiff_plain;f=drivers%2Fgpu%2Fdrm%2Fdisplay%2Fdrm_dp_helper.c;h=d046dfa79504f9c5368aaf2a0bd87c2e1d84f4b7;hb=ca7a1d0d18acbd2b49aeec5265083d05c49222df;hp=8d6ce46471ae6161c601ae0488fb65dda48f396b;hpb=3fe262eca5bd97cbde65ec71b4491c6461ffc7a7;p=thirdparty%2Fkernel%2Fstable.git

diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c
index 8d6ce46471ae..d046dfa79504 100644
--- a/drivers/gpu/drm/display/drm_dp_helper.c
+++ b/drivers/gpu/drm/display/drm_dp_helper.c
@@ -4055,3 +4055,33 @@ int drm_dp_bw_channel_coding_efficiency(bool is_uhbr)
 		return 800000;
 }
 EXPORT_SYMBOL(drm_dp_bw_channel_coding_efficiency);
+
+/**
+ * drm_dp_max_dprx_data_rate - Get the max data bandwidth of a DPRX sink
+ * @max_link_rate: max DPRX link rate in 10kbps units
+ * @max_lanes: max DPRX lane count
+ *
+ * Given a link rate and lanes, get the data bandwidth.
+ *
+ * Data bandwidth is the actual payload rate, which depends on the data
+ * bandwidth efficiency and the link rate.
+ *
+ * Note that protocol layers above the DPRX link level considered here can
+ * further limit the maximum data rate. Such layers are the MST topology (with
+ * limits on the link between the source and first branch device as well as on
+ * the whole MST path until the DPRX link) and (Thunderbolt) DP tunnels -
+ * which in turn can encapsulate an MST link with its own limit - with each
+ * SST or MST encapsulated tunnel sharing the BW of a tunnel group.
+ *
+ * Returns the maximum data rate in kBps units.
+ */
+int drm_dp_max_dprx_data_rate(int max_link_rate, int max_lanes)
+{
+	int ch_coding_efficiency =
+		drm_dp_bw_channel_coding_efficiency(drm_dp_is_uhbr_rate(max_link_rate));
+
+	return DIV_ROUND_DOWN_ULL(mul_u32_u32(max_link_rate * 10 * max_lanes,
+					      ch_coding_efficiency),
+				  1000000 * 8);
+}
+EXPORT_SYMBOL(drm_dp_max_dprx_data_rate);