[PATCH net] can: rockchip_canfd: stop bus-off restart before closing the device

[Cunhao Lu]

Hi,

>  - How the issue was discovered, e.g. hit in production, hit during
>    development, syzbot report, manual code inspection, LLM or static
>    analysis tool scan.

Thanks for pointing this out. This work started with a real failure on a
production robot, rather than a general scan for potential driver bugs.

The production system used a LubanCat-5IO with an RK3588, running a
6.18.55-current-rockchip64 PREEMPT_RT kernel with local CAN patches. Its
1 Mbit/s CAN bus connected four CANopen motors operating at 100 Hz and
four sensors operating at 20 Hz.

>  - Whether the issue was actually triggered, or is only theoretical
>    (e.g. found by code inspection). If it was triggered please include
>    the symptoms, like the stack trace or error messages.

The observed failure was a persistent TX stall: RX continued, but the TX
queue remained stopped and subsequent sends returned ENOBUFS. The
interface still reported ERROR-ACTIVE, and the hardware indicated neither
a bus-off condition nor a pending TX request.

I will submit two patches for this issue; this is the first one.

This patch is not a direct fix for that failure. It fixes a race
that was already present in the driver and that I found during
fault-injection testing of the echo-loss fix: close_candev() cancels
restart_work only after the IRQ has been freed and the controller has
been stopped, so a queued bus-off restart can re-enable the controller
and its interrupts after IRQ teardown, and can requeue timestamp work
that may later access registers after runtime suspend has disabled the
clocks. The second patch builds on this serialization and addresses the
echo-loss stall itself.

Regards,
Cunhao Lu