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* [PATCH v2 0/2] drm/dp/mst: fix MST payload PBN accounting
@ 2026-09-22  9:26 Xiao Lu
  2026-09-22  9:26 ` [PATCH v2 1/2] drm/i915/dp: fix PBN in ALLOCATE_PAYLOAD request to use actual video bandwidth Xiao Lu
                   ` (5 more replies)
  0 siblings, 6 replies; 13+ messages in thread
From: Xiao Lu @ 2026-09-22  9:26 UTC (permalink / raw)
  To: intel-gfx
  Cc: dri-devel, jani.nikula, joonas.lahtinen, rodrigo.vivi,
	tvrtko.ursulin, lyude, David.Francis, Xiao Lu

v2: Send the two related patches together as a series, as requested
by Jani. No code changes from v1.

This series fixes two related issues in MST payload bandwidth
accounting that together caused 4K@60Hz to fail alongside two
1080p@60Hz displays in a 3-display MST daisy-chain topology
(PS8650 hub -> ViewSonic VP2468 x2 -> Lenovo Pro 27UD-10).

Patch 1 fixes the PBN value passed in the ALLOCATE_PAYLOAD sideband
request. The driver was using a TU-aligned PBN (e.g. 537) instead of
the actual video stream bandwidth (e.g. 496 for 1080p@59.94Hz),
inflating the requested PBN and causing -ENOSPC failures for
configurations that should fit within the available link bandwidth.

Patch 2 tracks the allocated_pbn returned in the ALLOCATE_PAYLOAD
reply, and uses it alongside @pbn for bandwidth limit checks. This
ensures that any per-hop capacity constraints from intermediate MST
branches are correctly reflected in the source-side bandwidth check.

Xiao Lu (2):
  drm/i915/dp: fix PBN in ALLOCATE_PAYLOAD request to use actual video bandwidth
  drm/dp/mst: track allocated_pbn from ALLOCATE_PAYLOAD reply

 drivers/gpu/drm/display/drm_dp_mst_topology.c | 24 ++++++++++++++----
 drivers/gpu/drm/i915/display/intel_dp_mst.c   | 24 +++++++++++------
 include/drm/display/drm_dp_mst_helper.h       | 10 +++++++
 3 files changed, 46 insertions(+), 12 deletions(-)

-- 
2.43.0

^ permalink raw reply	[flat|nested] 13+ messages in thread

end of thread, other threads:[~2026-09-24  9:58 UTC | newest]

Thread overview: 13+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-09-22  9:26 [PATCH v2 0/2] drm/dp/mst: fix MST payload PBN accounting Xiao Lu
2026-09-22  9:26 ` [PATCH v2 1/2] drm/i915/dp: fix PBN in ALLOCATE_PAYLOAD request to use actual video bandwidth Xiao Lu
2026-09-22  9:35   ` sashiko-bot
2026-09-22  9:26 ` [PATCH v2 2/2] drm/dp_mst: Track allocated_pbn from ALLOCATE_PAYLOAD down-reply Xiao Lu
2026-09-22  9:41   ` sashiko-bot
2026-09-22  9:35 ` [PATCH v2 0/2] drm/dp/mst: fix MST payload PBN accounting Jani Nikula
2026-09-22 12:30 ` ✓ i915.CI.BAT: success for " Patchwork
2026-09-22 23:22 ` ✗ i915.CI.Full: failure " Patchwork
2026-09-24  9:43 ` [PATCH v3 0/2] drm/i915/dp: Fix MST " Xiao Lu
2026-09-24  9:43   ` [PATCH v3 1/2] drm/i915/dp: fix PBN in ALLOCATE_PAYLOAD request to use actual video bandwidth Xiao Lu
2026-09-24  9:51     ` sashiko-bot
2026-09-24  9:43   ` [PATCH v3 2/2] drm/dp_mst: Track allocated_pbn from ALLOCATE_PAYLOAD down-reply Xiao Lu
2026-09-24  9:57     ` sashiko-bot

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