[PATCH v6 0/3] gpu: nova-core: retain the GSP-RM log buffers

[Vladislav Zaharov <vladazaharova2018@gmail.com>]

The GSP-RM log buffers are exposed through debugfs, but they are DMA
allocations of the device, so they go away as soon as the GPU is unbound,
and in particular when probe() fails. That is the case todo.rst asks
about, and the one where a GSP log is most useful.

Patch 1 moves the debugfs root into the module data. Patch 2 adds a
gsp_keep_logs module parameter: when it is set, whatever the GSP wrote
is copied into module memory and kept under a "retained" directory until
the module is unloaded. Patch 3 drops the completed item from todo.rst.

v5 got no comments, so this version only carries one fix and a rebase.

Changes since v5:
 - keep the "put" pointer read before the barrier in the copy, rather
   than the one the copy reads again, which is not ordered against the
   rest of the data (reported by the Sashiko review bot)
 - rebase onto current drm-rust-next

Tested on a GB203 on top of drm-rust-next with the TLV firmware images:

  - without gsp_keep_logs nothing changes, and no "retained" directory
    is created;
  - with gsp_keep_logs=1, retained/<BDF>/{loginit,logintr,logrm} hold
    the full 64 KiB of each buffer after unbind;
  - binding again does not disturb the copies, and a second unbind
    replaces them, leaving one set;
  - with a failure injected after the GSP has booted, probe() fails with
    -EINVAL and the logs of that attempt are still readable;
  - with a failure injected into the driver registration, the module
    fails to load, leaves no debugfs directory behind, and the next load
    works;
  - repeated load/unload cycles leave nothing behind.

No warnings or oopses in dmesg. Each patch builds on its own, and the
series is clean with CLIPPY=1, rustfmtcheck and checkpatch --strict
(apart from the MAINTAINERS note for the new file, which is already
covered by "F: drivers/gpu/nova-core/").

v5: https://lore.kernel.org/nova-gpu/20260923045551.229259-1-vladazaharova2018@gmail.com/

Vladislav Zaharov (3):
  gpu: nova-core: move the debugfs root into the module data
  gpu: nova-core: gsp: retain the GSP-RM log buffers after unbind
  Documentation: nova: remove completed GSP log buffer task

 Documentation/gpu/nova/core/todo.rst   |  12 --
 drivers/gpu/nova-core/gsp.rs           | 100 ++--------
 drivers/gpu/nova-core/gsp/logbuffer.rs | 255 +++++++++++++++++++++++++
 drivers/gpu/nova-core/nova_core.rs     | 101 ++++++++--
 4 files changed, 356 insertions(+), 112 deletions(-)
 create mode 100644 drivers/gpu/nova-core/gsp/logbuffer.rs


base-commit: 5a1b7121a6c4db6c0239d3ac3fd1c2bb33a40025
-- 
2.56.0