Re: [PATCH] starfire reads irq before pci_enable_device.

[Jes Sorensen]

>>>>> "Gérard" == Gérard Roudier <[e-mail]> writes:

Gérard> On Fri, 9 Feb 2001, Alan Cox wrote:

>> DMA to main memory normally invalidates those lines in the CPU
>> cache rather than the cache snooping and updating its view of them.

Gérard> In PCI, it is the Memory Write and Invalidate PCI transaction
Gérard> that is intended to allow core-logics to optimize DMA this
Gérard> way. For normal Memory Write PCI transactions or when the
Gérard> core-logic is aliasing MWI to MW, the snooping may well
Gérard> happen. All that stuff, very probably, varies a lot depending
Gérard> on the core-logic.

In fact one has to look out for this and disable the feature in some
cases. On the acenic not disabling Memory Write and Invalidate costs
~20% on performance on some systems.

Jes