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* [PATCH] drm/i915/mst: add beginnings of DP MST documentation
@ 2024-11-25 15:19 Jani Nikula
  2024-11-25 16:10 ` ✗ i915.CI.BAT: failure for " Patchwork
                   ` (2 more replies)
  0 siblings, 3 replies; 5+ messages in thread
From: Jani Nikula @ 2024-11-25 15:19 UTC (permalink / raw)
  To: intel-gfx; +Cc: jani.nikula, imre.deak

Add a little bit of documentation around DP MST. This is nowhere near
complete nor does it have enough detail. But it's better than nothing,
and hopefully gives people a basic grasp of what's going on.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp_mst.c | 32 +++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
index c59c2c14679c..a9ce8b3a7ff5 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
@@ -53,6 +53,38 @@
 #include "intel_vdsc.h"
 #include "skl_scaler.h"
 
+/*
+ * DP MST (DisplayPort Multi-Stream Transport)
+ *
+ * MST support on the source depends on the platform and port. DP initialization
+ * sets up MST for each MST capable encoder. This will become the primary
+ * encoder for the port.
+ *
+ * MST initialization of each primary encoder creates MST stream encoders, one
+ * per pipe, and initializes the MST topology manager. The MST stream encoders
+ * are sometimes called "fake encoders", because they're virtual, not
+ * physical. Thus there are (number of MST capable ports) x (number of pipes)
+ * MST stream encoders in total.
+ *
+ * Decision to use MST for a sink happens at detect on the connector attached to
+ * the primary encoder, and this will not change while the sink is connected. We
+ * always use MST when possible, including for SST sinks with sideband messaging
+ * support.
+ *
+ * The connectors for the MST streams are added and removed dynamically by the
+ * topology manager. Their connection status is also determined by the topology
+ * manager.
+ *
+ * On hardware, each transcoder may be associated with a single DDI
+ * port. Multiple transcoders may be associated with the same DDI port only if
+ * the port is in MST mode.
+ *
+ * On TGL+, all the transcoders streaming on the same DDI port will indicate a
+ * primary transcoder; the TGL_DP_TP_CTL and TGL_DP_TP_STATUS registers are
+ * relevant only on the primary transcoder. Prior to that, they are port
+ * registers.
+ */
+
 /* From fake MST stream encoder to primary encoder */
 static struct intel_encoder *to_primary_encoder(struct intel_encoder *encoder)
 {
-- 
2.39.5


^ permalink raw reply related	[flat|nested] 5+ messages in thread

end of thread, other threads:[~2024-12-10 11:12 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2024-11-25 15:19 [PATCH] drm/i915/mst: add beginnings of DP MST documentation Jani Nikula
2024-11-25 16:10 ` ✗ i915.CI.BAT: failure for " Patchwork
2024-12-04 15:40 ` [PATCH] " Imre Deak
2024-12-10 11:11   ` Jani Nikula
2024-12-05 20:41 ` ✗ i915.CI.BAT: failure for drm/i915/mst: add beginnings of DP MST documentation (rev2) Patchwork

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