Re: [Linux-ia64] Re: PCI DAC routines for SN

From: Grant Grundler <grundler_at_cup.hp.com>
Date: 2002-04-24 07:11:37
Jesse Barnes wrote:
> He was the one that implemented it I thought.  His assertion was that
> since most chipsets don't handle 64 bit coherent allocations well, the
> consistent interface should be forced to return a 32 bit address (is
> that right Dave?).

Right - HP recently changed ZX1 support based on the same assertion.
And for the drivers I'm aware of (eg tg3, sym53c8xx), Dave is right.

...
> otherwise I'd like to leave it up to the platform
> (i.e. ia64/sn could return a 64 bit address and sparc64 could do 32).

This is not feasible. The driver/device will use/support the same number
of address bits regardless of architecture. If the architecture provides
fewer bits than the driver/device supports, no problem obviously.

I'm curious to see what happens with the pci_dac_alloc_consistent() idea.

grant
Received on Wed Apr 24 10:46:47 2002

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