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

From: Alan Cox
Date: Wed Jun 28 2006 - 13:46:09 EST


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

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