[PATCH 06/14] drm/amd/display: Use dc helpers to compute timeslot distribution

[David Francis]

We were using drm helpers to convert a timing into its
bandwidth, its bandwidth into pbn, and its pbn into timeslots

These helpers
-Did not take DSC timings into account
-Used the link rate and lane count of the link's aux device,
 which are not the same as the link's current cap
-Did not take FEC into account (FEC reduces the PBN per timeslot)

Use the DC helpers (dc_bandwidth_in_kbps_from_timing,
dc_link_bandwidth_kbps) instead

Cc: Jerry Zuo <Jerry.Zuo at amd.com>
Signed-off-by: David Francis <David.Francis at amd.com>
---
 .../amd/display/amdgpu_dm/amdgpu_dm_helpers.c | 41 ++++---------------
 1 file changed, 8 insertions(+), 33 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
index 5f2c315b18ba..b32c0790399a 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
@@ -189,8 +189,8 @@ bool dm_helpers_dp_mst_write_payload_allocation_table(
 	int slots = 0;
 	bool ret;
 	int clock;
-	int bpp = 0;
 	int pbn = 0;
+	int pbn_per_timeslot;
 
 	aconnector = (struct amdgpu_dm_connector *)stream->dm_stream_context;
 
@@ -205,40 +205,15 @@ bool dm_helpers_dp_mst_write_payload_allocation_table(
 	mst_port = aconnector->port;
 
 	if (enable) {
-		clock = stream->timing.pix_clk_100hz / 10;
-
-		switch (stream->timing.display_color_depth) {
-
-		case COLOR_DEPTH_666:
-			bpp = 6;
-			break;
-		case COLOR_DEPTH_888:
-			bpp = 8;
-			break;
-		case COLOR_DEPTH_101010:
-			bpp = 10;
-			break;
-		case COLOR_DEPTH_121212:
-			bpp = 12;
-			break;
-		case COLOR_DEPTH_141414:
-			bpp = 14;
-			break;
-		case COLOR_DEPTH_161616:
-			bpp = 16;
-			break;
-		default:
-			ASSERT(bpp != 0);
-			break;
-		}
-
-		bpp = bpp * 3;
-
-		/* TODO need to know link rate */
+		clock = dc_bandwidth_in_kbps_from_timing(&stream->timing);
 
-		pbn = drm_dp_calc_pbn_mode(clock, bpp);
+		/* dc_bandwidth_in_kbps_from_timing already takes bpp into account */
+		pbn = drm_dp_calc_pbn_mode(clock, 1);
 
-		slots = drm_dp_find_vcpi_slots(mst_mgr, pbn);
+		/* Convert kilobits per second / 64 (for 64 timeslots) to pbn (54/64 megabytes per second) */
+		pbn_per_timeslot = dc_link_bandwidth_kbps(
+				stream->link, dc_link_get_link_cap(stream->link)) / (8 * 1000 * 54);
+		slots = DIV_ROUND_UP(pbn, pbn_per_timeslot);
 		ret = drm_dp_mst_allocate_vcpi(mst_mgr, mst_port, pbn, slots);
 
 		if (!ret)
-- 
2.17.1