[PATCH 0/2] drm/nouveau: nv04 FIFO cleanup + recovery for Tesla

[Marek Czernohous <mczernohous@gmail.com>]

Hi all,

Two-patch series for the legacy nv04_fifo path covering Tesla
(MCP77/MCP79 and G80-GT218). Daily-driven on the reference NVAC
hardware (Apple Mac mini Late 2009, GeForce 9400M) since 2026-05-05.

Patch 1 demotes a benign CACHE_ERROR that fires once per Mesa session
start on Tesla GPUs. The Mesa NV50 userspace driver issues a method-
0x0060 / data-0xbeef02xx binding probe that recovers cleanly via
nv04_fifo_swmthd(), but currently logs at error level on every X or
Wayland session, dominating dmesg noise on this hardware class. This
clears the channel for patch 2 to identify real faults from noise.

Patch 2 adds a two-tier fault-recovery path for Tesla FIFO faults:

  Tier 1 (per fault). Look up the channel via nvkm_chan_get_chid,
  call nvkm_chan_error(chan, true), fire tracepoint
  nouveau:fifo_chan_killed. Idempotent through the existing
  chan->errored short-circuit.

  Tier 2 (sliding window). When the per-fifo fault count in a
  configurable window reaches the threshold, schedule a worker that
  calls drm_dev_wedged_event(drm, DRM_WEDGE_RECOVERY_REBIND, NULL)
  and fires tracepoint nouveau:fifo_dev_wedged. Worker context is
  needed because kobject_uevent_env may sleep.

Motivation: Fermi+ gets channel-kill and device-wedge automatically
through nvkm_runl_rc; Tesla was feature-frozen before the DRM wedge
uAPI existed. Three observable consequences on the reference
hardware:

  1. Silent state corruption (channel produces wrong output after a
     fault, no notice to userspace).
  2. Observability gap (no counters, tracepoints, or wedge event,
     only dmesg).
  3. Repeated-fault loop (the log-and-reset cycle repeats forever on
     a persistently faulting channel instead of killing it).

Validation. A debugfs fault-injector (kept on a separate
DO-NOT-MERGE branch, not part of this submission) was used to drive
both Tier-1 and Tier-2 paths through their full state space. Phases
1-5 of the test plan were exercised that way. Phase 6 (no manual
injection, real workload soak) ran 2026-05-05 through 2026-05-13:
one organic DRM_WEDGE_RECOVERY_REBIND event was captured on
2026-05-05 09:08; the rest of the soak was fault-free.

Companion userland tool nouveau-pstate-daemon v0.2.0 [1] subscribes
to the WEDGED=rebind uevent in log-only mode and was used to confirm
end-to-end propagation through udev.

Module parameters:

  nouveau.fifo_wedge_count     (uint, 0..32, default 10)
  nouveau.fifo_wedge_window_ms (uint, 100..600000, default 60000)

Setting fifo_wedge_count=0 disables Tier-2 entirely while keeping
Tier-1 channel-kill active.

A note on MAINTAINERS. The series adds a new file
drivers/gpu/drm/nouveau/nvkm/engine/fifo/recover.c. The change is
covered by the existing nouveau MAINTAINERS section
(drivers/gpu/drm/nouveau/), so no MAINTAINERS update is included.
checkpatch.pl flags this as a hint; it is not load-bearing.

This is a follow-up to the April 9 NVAC stability series [2], which
is still awaiting review. The two patches here are independent of
that series and apply against current Linus master.

[1] https://github.com/hibbes/nouveau-pstate-daemon (v0.2.0)
[2] https://lore.kernel.org/dri-devel/20260409-nouveau-nvac-stability-series

Marek Czernohous (2):
  drm/nouveau/fifo/nv04: filter benign CACHE_ERROR from Mesa NV50 bind
    probe
  drm/nouveau/fifo: add recovery path for Tesla cache_error/dma_pusher

 .../drm/nouveau/include/nvkm/engine/fifo.h    |  12 ++
 .../include/trace/events/nouveau_fifo.h       |  58 +++++++++
 drivers/gpu/drm/nouveau/nouveau_drm.c         |  29 +++++
 .../gpu/drm/nouveau/nvkm/engine/fifo/Kbuild   |   1 +
 .../gpu/drm/nouveau/nvkm/engine/fifo/base.c   |   3 +
 .../gpu/drm/nouveau/nvkm/engine/fifo/nv04.c   |  29 ++++-
 .../gpu/drm/nouveau/nvkm/engine/fifo/priv.h   |  10 ++
 .../drm/nouveau/nvkm/engine/fifo/recover.c    | 121 ++++++++++++++++++
 8 files changed, 257 insertions(+), 6 deletions(-)
 create mode 100644 drivers/gpu/drm/nouveau/include/trace/events/nouveau_fifo.h
 create mode 100644 drivers/gpu/drm/nouveau/nvkm/engine/fifo/recover.c


base-commit: 1f63dd8ca0dc05a8272bb8155f643c691d29bb11
-- 
2.53.0