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

[lyude@redhat.com]

Hey! I truly apologize for asking, and thank you tremendously in
advance if the answer is no. But I had to check since I haven't seen
you around before, and these are unusually long commit messages:

These patches were written by a person correct? If not, you need to
follow the coding assistants guidelines here:

https://docs.kernel.org/process/coding-assistants.html

On Wed, 2026-05-13 at 19:50 +0200, Marek Czernohous wrote:
> 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