Re: [PATCH] (Longhaul 1/5) PCI: Protect bus master DMA from Longhaul by rw semaphores

Alan Cox
2006-06-28T17:47:43Z

Ar Mer, 2006-06-28 am 10:34 -0700, ysgrifennodd Greg KH:
> Eeek! You mean the longhaul driver can change the frequency of the PCI
> bus? Oh, that's a recipe for disaster...

Not as I understand the docs, and that would be unfixable. Some C3
setups do however appear to "fall off the bus" during transitions which
means if BMDMA is active things get confused.

I am still not clear if this is just cache corruption through us not
listening or whether we genuinely need to halt. In the former case
flushing and disabling the CPU caches ought to be sufficient.

Alan