spi: spi-pci1xxxx: quiesce DMA engines on transfer timeout

If a DMA-mapped transfer times out waiting for DMA_TERM and neither DMA
abort interrupt arrived, pci1xxxx_spi_transfer_with_dma() returns
through the error label while both DMA engines are still enabled, the
done/abort interrupt status is still armed and the transfer state
(p->xfer, p->tx_sgl, p->rx_sgl) is still registered.

The ISRs keep firing afterwards: they reprogram the DMA engines from
p->tx_sgl / p->rx_sgl and signal completion through p->xfer and
p->spi_xfer_done, all of which the SPI core is free to unmap or reuse
once transfer_one() has returned, which is a use-after-free. A late
done interrupt can also start the next transfer queued behind the
failed one.

Stop both DMA engines, drain the pending done/abort interrupt status
and synchronize the DMA IRQs before dropping the in-progress state and
the transfer pointers, and re-enable the engines afterwards so that
subsequent transfers keep working. The engines are only turned back on
once both were confirmed to have stopped: re-enabling an engine that
failed to stop would cancel the pending stop request and let it keep
running into buffers the SPI core is about to unmap or free, which is
exactly the window this patch closes. An engine that failed to stop is
left disabled, as the abort paths already do.

The DMA interrupt status and mask registers are shared between the two
SPI instances, so the cleanup drains only this instance's done/abort
status bits instead of masking the interrupt lines, which would also
suppress the peer instance's completion interrupts.

Also make the DMA ISRs ignore interrupts while no transfer is in
progress so that a stray MSI after the cleanup can no longer act on
the cleared state.

No PCI1XXXX hardware was available for testing and QEMU has no model
of this PCIe part, so the timeout path was exercised with a userspace
replica of the timeout branch and the DMA ISRs, with the register and
interrupt accesses mocked: on the unfixed code both a wedged engine
that clears after the timeout and a late done interrupt touch the
freed transfer state, while with this fix applied neither does and an
engine that failed to stop is left disabled.  The module was also
loaded and unloaded in a QEMU x86_64 guest running a kernel with this
fix applied.

Fixes: 9538edeb72c9 ("spi: mchp-pci1xxxx: DMA support for copying data to and from SPI Buf")
Cc: stable@vger.kernel.org # 6.8+
Signed-off-by: Weibin Liu <liuwb@xiaopeng.com>
Link: https://patch.msgid.link/20261016020036.1333548-1-liuwb@xiaopeng.com
Signed-off-by: Mark Brown <broonie@kernel.org>

0 files changed, 0 insertions, 0 deletions