5.1beta2 on Alpha ES40 w/ 32GB pys ram

[Bernd Walter]

On Mon, Jun 16, 2003 at 09:19:19PM -0400, Andrew Gallatin wrote:
> 
> Jeff Roberson writes:
>  > On Wed, 4 Jun 2003, Andrew Gallatin wrote:
>  > 
>  > >
>  > >
>  > > Andrea Cocito writes:
>  > >  > Hallo,
>  > >  >
>  > >  > I have a little (??) problem trying to boot FreeBSD 5.1beta2
>  > >  > on an ES40 with 32 gigs of  physical RAM, this is the status:
>  > >  >
>  > >
>  > > You have to limit physical memory to 2GB or less.  Otherwise, DMAs
>  > > won't work.
>  > >
>  > > Drew
>  > 
>  > Is this because we dont program the TLB on the DMA controller?  I heard
>  > rumors that sparc64 has code to handle all of this for their chipsets.  If
>  > they have the infrastructure it may not be hard to port.
>  > 
> 
> We program it, but we do not take full advantage of it:
> 
> Most alphas have 4 DMA windows.  We typically use 1 window for ISA

Do you have an overview of which ones don't have 4 windows?
Is the direct map sufficient for them or can we increase the ISA map
size in such a case?

> dma, meaning we can do zero-copy (no bounce buffer) DMA to any ISA
> device.  This is only 16MB in size.
> 
> We use another window as a 'direct map' window, meaning we map
> physical addresses 0..1GB (or 0..2GB) into PCI address space,
> generally at offset 1GB in PCI address space.

What are the reasons for this difference?
Is it just because of SRM interaction or some chipset limitation?

> We should use another window for 32-bit PCI DMA, and we should enable
> the "monster window" bit, so that devices which are DAC (64-bit)
> address capable don't need to deal with the TLB on the DMA
> controller.   We don't currently do either.

In the first step I would say we should start checking cards for DAC
support and if there are enough of them then do the monster window
thing first.
I asume it's not that critical for >2G machine owners to replace non DAC
cards, especially as I believe many non DAC cards have currently non
busdma drivers as well.

The S/G map can be done later if still required.
Maybe with a tuneable size as a 4G map takes 4M map - checked for 21172.

-- 
B.Walter                   BWCT                http://www.bwct.de
ticso at bwct.de                                  info at bwct.de