Subject: Re: Still Pyxis DMA trouble
To: Wilko Bulte <>
From: Olaf Seibert <>
List: port-alpha
Date: 01/17/2001 23:57:01
On Wed 17 Jan 2001 at 22:03:25 +0100, Wilko Bulte wrote:
> On Wed, Jan 17, 2001 at 09:54:55PM +0100, Olaf Seibert wrote:
> > It seems that even in 1.5 the Pyxis DMA workaround is not perfect yet.
> > I was careful to try the netbsd.ram kernel, and it did not work properly
> There are multiple ECO levels on the MX5 so you might have hardware that is
> not up to the latest rev. Just a guess of course

That is of course quite possible.

When browsing through the source, I found the following comment a bit

 * Flush the scatter/gather TLB on broken Pyxis chips.
         * Now, read from PCI dense memory space at offset 128M (our
         * target window base), skipping 64k on each read.  This forces
         * S/G TLB misses.
         * XXX Looks like the TLB entries are `not quite LRU'.  We need
         * XXX to read more times than there are actual tags!
in arch/alpha/pci/cia_dma.c. A thing like this sounds like it could differ
between revisions - maybe my version needs still more forced TLB misses?
Or am I talking nonsense here?

> W/
___ Olaf 'Rhialto' Seibert - rhialto@polder --Soep van de dag, wat zal dat zijn
\X/     --wat kan dat wezen, beter maar het ergste vrezen -Boy Bensdorp