From: Marek Czernohous <[email protected]>
(v3 follows up on this morning's v2 posting twice over: those mails
went out with a duplicated in-body From: line and broken threading due
to a send-email misconfiguration on my side, and the Sashiko AI review
correctly pointed out that the new guard in 2/2 sat below a connector
dereference it was meant to protect. Patch 1 is unchanged; please
disregard the earlier copies. Previous posting:
https://lore.kernel.org/all/[email protected]/ )
This is v3 of the NVAC (MCP79/MCP7A) stability series, narrowed to the
two changes that are genuinely stable material and reworked after review
plus an independent second-machine test.
The original v1 [1] was a three-patch series. Since then it has had a
two-month daily-driver soak on my Apple Mac mini (early 2009, MCP79) and an
independent
test by Fab Stz on a second machine (iMac9,1 / MCP79, 6.12.90, X11/KDE 6),
who confirmed the system is more stable with the series and provided a
Tested-by. After an internal review pass:
Patch 1 (MSI rearm): NVAC re-arms MSI through the MMIO mirror of PCI
config space, which is unreliable on this IGP; a missed re-arm leaves
the interrupt line dead and the GPU wedges. v1 switched the whole
shared g94_pci_func (ten chipsets); v2 narrows this to a dedicated
mcp79 pci func so only the tested chipset (0xac) changes, matching the
existing g92 precedent. The stable tag is annotated v6.16+ (the new
file uses the .cfg member added there); older LTS trees want the
era-specific one-line msi_rearm switch instead, offered in 1/2.
Patch 2 (SOR disable NULL guard): nv50_sor_atomic_disable() can run with
a NULL nv_encoder->crtc under Wayland session teardown / VT switches,
and because the deref goes through container_of() the NULL becomes a
bogus pointer that faults. v2 restores the guard as drm_WARN_ON_ONCE()
and, unlike v1, does not call nvif_outp_release() in the early return
(that path is owned by the commit_tail release loop; the v1 form could
release twice and detach the OR before the disable flush).
The v1 patch 3 (HPD link-check retry) is intentionally dropped from this
series: it is a behavioral workaround that sleeps under mode_config.mutex,
not an obviously-correct fix, so it does not meet the stable bar. I will
revisit it separately if it is still needed.
Both patches carry Fixes: and Cc: stable tags. Per-patch changelogs
are under the --- in each patch.
Disclosure: this work was done with assistance from an AI coding assistant
(Anthropic's Claude, Opus 4.7 and 4.8); the analysis and conclusions are
mine and have been verified on hardware. Each patch also carries an
Assisted-by trailer to that effect.
[1] https://lore.kernel.org/nouveau/[email protected]/
Marek Czernohous (2):
drm/nouveau/pci: use config-space MSI rearm on MCP79/MCP7A (NVAC)
drm/nouveau/kms: guard NULL crtc in nv50_sor_atomic_disable()
drivers/gpu/drm/nouveau/dispnv50/disp.c | 30 +++++++++++++---
.../gpu/drm/nouveau/include/nvkm/subdev/pci.h | 1 +
.../gpu/drm/nouveau/nvkm/engine/device/base.c | 2 +-
.../gpu/drm/nouveau/nvkm/subdev/pci/Kbuild | 1 +
.../gpu/drm/nouveau/nvkm/subdev/pci/mcp79.c | 35 +++++++++++++++++++
5 files changed, 63 insertions(+), 6 deletions(-)
create mode 100644 drivers/gpu/drm/nouveau/nvkm/subdev/pci/mcp79.c
--
2.53.0
