[Cbe-oss-dev] [patch 08/16] powerpc and x86_64: Initial port of PCIe endpoint device driver for Axon

[Jesse P Arroyo]

Murali Iyer <mniyer at vnet.ibm.com> wrote on 03/13/2008 10:04:29 AM:
> > Nothing in the kernel guarantees that the memory returned from
> > dma_alloc_coherent() is aligned. Even if it is, the DMA address
> > may not be aligned in the same way. If you require strict alignment,
> > your best option would be to allocate an extra 64kb and manually
> > align on the bus address.
> I suspect it has to be aligned 16 bytes boundary.. need to check.
> 
According to the spec, the mailbox FIFO buffer must be aligned on a
sizeof(buffer) due to the hardware wrapping logic.
So, if we have a 64kB buffer, we need it aligned to a 64kB address.