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)
For converting timing into PBN, add a new function
drm_dp_calc_pbn_mode_dsc that handles the DSC case
For converting PBN into time slots, amdgpu doesn't use the
'correct' atomic method (drm_dp_atomic_find_vcpi_slots), so
don't add a new helper to cover our approach. Use the same
means of calculating pbn per time slot as the DSC code.
v2: Add drm helper for clock to pbn conversion
Cc: Jerry Zuo <Jerry.Zuo@xxxxxxx>
Cc: Nicholas Kazlauskas <nicholas.kazlauskas@xxxxxxx>
Signed-off-by: David Francis <David.Francis@xxxxxxx>
---
.../amd/display/amdgpu_dm/amdgpu_dm_helpers.c | 18 +++++---
drivers/gpu/drm/drm_dp_mst_topology.c | 41 +++++++++++++++++++
include/drm/drm_dp_mst_helper.h | 2 +-
3 files changed, 54 insertions(+), 7 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..dfa99e0d6e64 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, bpp = 0;
aconnector = (struct amdgpu_dm_connector *)stream->dm_stream_context;
@@ -208,7 +208,6 @@ bool dm_helpers_dp_mst_write_payload_allocation_table(
clock = stream->timing.pix_clk_100hz / 10;
switch (stream->timing.display_color_depth) {
-
case COLOR_DEPTH_666:
bpp = 6;
break;
@@ -234,11 +233,18 @@ bool dm_helpers_dp_mst_write_payload_allocation_table(
bpp = bpp * 3;
- /* TODO need to know link rate */
-
- pbn = drm_dp_calc_pbn_mode(clock, bpp);
+#ifdef CONFIG_DRM_AMD_DC_DSC_SUPPORT
+ if (stream->timing.flags.DSC)
+ pbn = drm_dp_calc_pbn_mode_dsc(clock,
+ stream->timing.dsc_cfg.bits_per_pixel);
+ else
+#endif
+ pbn = drm_dp_calc_pbn_mode(clock, bpp);
- 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)
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 398e7314ea8b..d789b7af7dbf 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -3588,6 +3588,47 @@ static int test_calc_pbn_mode(void)
return 0;
}
+/**
+ * drm_dp_calc_pbn_mode_dsc() - Calculate the PBN for a mode with DSC enabled.
+ * @clock: dot clock for the mode
+ * @dsc_bpp: dsc bits per pixel x16 (e.g. dsc_bpp = 136 is 8.5 bpp)
+ *
+ * This uses the formula in the spec to calculate the PBN value for a mode,
+ * given that the mode is using DSC
+ */
+int drm_dp_calc_pbn_mode_dsc(int clock, int dsc_bpp)
+{
+ u64 kbps;
+ s64 peak_kbps;
+ u32 numerator;
+ u32 denominator;
+
+ kbps = clock * dsc_bpp;
+
+ /*
+ * margin 5300ppm + 300ppm ~ 0.6% as per spec, factor is 1.006
+ * The unit of 54/64Mbytes/sec is an arbitrary unit chosen based on
+ * common multiplier to render an integer PBN for all link rate/lane
+ * counts combinations
+ * calculate
+ * peak_kbps *= (1/16) bppx16 to bpp
+ * peak_kbps *= (1006/1000)
+ * peak_kbps *= (64/54)
+ * peak_kbps *= 8 convert to bytes
+ *
+ * Divide numerator and denominator by 16 to avoid overflow
+ */
+
+ numerator = 64 * 1006 / 16;
+ denominator = 54 * 8 * 1000 * 1000;
+
+ kbps *= numerator;
+ peak_kbps = drm_fixp_from_fraction(kbps, denominator);
+
+ return drm_fixp2int_ceil(peak_kbps);
+}
+EXPORT_SYMBOL(drm_dp_calc_pbn_mode_dsc);
+
/* we want to kick the TX after we've ack the up/down IRQs. */
static void drm_dp_mst_kick_tx(struct drm_dp_mst_topology_mgr *mgr)
{
diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
index 2ba6253ea6d3..ddb518f2157a 100644
--- a/include/drm/drm_dp_mst_helper.h
+++ b/include/drm/drm_dp_mst_helper.h
@@ -611,7 +611,7 @@ struct edid *drm_dp_mst_get_edid(struct drm_connector *connector, struct drm_dp_
int drm_dp_calc_pbn_mode(int clock, int bpp);
-
+int drm_dp_calc_pbn_mode_dsc(int clock, int dsc_bpp);
bool drm_dp_mst_allocate_vcpi(struct drm_dp_mst_topology_mgr *mgr,
struct drm_dp_mst_port *port, int pbn, int slots);
--
2.17.1
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