From: Grant Grundler <iod00d@xxxxxx>
Subject: Re: tg3 support broken on PPC, a workaround
Date: Tue, 10 May 2005 16:21:32 -0700
> HP PCI bus controllers don't disconnect after a cacheline.
> The latest "LBA" (aka Mercury) will disconnect on 4k page
> boundaries. Alex Williamson confirmed.
Ok, good data point.
> Has anyone confirmed PPC, PPC64 and Alpha PCI/PCI-X bus
> controllers do the same?
> ISTR MMRBC (PCI-X only) allows one to specify
> shorter blocks. I'd have to look that up again.
BTW, I just noticed this in the NetBSD tigon3 driver:
* Must insure that we do not cross an 8K (bytes) boundary
* for DMA reads. Our highest limit is 1K bytes. This is a
* restriction on some ALPHA platforms with early revision
* 21174 PCI chipsets, such as the AlphaPC 164lx
PCI_SETBIT(sc, BGE_PCI_DMA_RW_CTL, BGE_PCI_READ_BNDRY_1024, 4);
This whole DMA boundary issue is turning into a very non-trivial one.
And if it is really true that plain PCI boundary crossing cannot be
controlled on non 5700/5701 chips, the tigon3 is certainly not going
to work reliably on systems such as the Alpha mentioned above.