DMA Crash on MPC8272

[Bill]

I am writing a Linux network device driver using Linux 2.4 with an
MPC8272 processor. I allocate buffers using kmalloc with the GFP_DMA
and GFP_KERNEL flags set. I DMA using these buffers to and from the
memory of a PCI device that is not a bus master. When I DMA from the
buffers to the PCI device, it does not crash, but when I DMA from the
PCI device to the buffers, the system crashes, sometimes immediately
and sometimes in as much as a half hour.

What could cause this difference in behavior based on the direction of
the DMA?

[John McCallum]

Hiya Bill,

[...] When I DMA from the
buffers to the PCI device, it does not crash, but when I DMA from the
PCI device to the buffers, the system crashes, sometimes immediately
and sometimes in as much as a half hour.
What could cause this difference in behavior based on the direction of
the DMA?

The last time something like this happened to me, it was because the
memory destination was wrong and I was overwriting part of the kernel.

Sounds like pretty similar behaviour.

Cheers,
John McCallum
Edinburgh