Write combining for PowerPC processors?

[Benjamin Herrenschmidt]

On Fri, 2004-12-10 at 14:12 -0800, Kendall Bennett wrote:

> Which would work if we flushed the CPU cache after we have compeleted all 
> software rendering, right? We have to support that anyway as a lot of 
> modern cards have write buffers that need to be flushed after software 
> rendering is done, so we could put that the same place in the code.

You can't easily "flush the CPU cache". You have to flush the cache
lines you have written....

> How do we enable caching? Is that something that needs to be done in the 
> northbridge also? 

No, that is done via the page tables attributes on the MMU, I suspect
you can control that with mprotect, but I'm not too sure.

> I assume either caching or write combining would be something for the 
> platform specific code in the Linux kernel, right?

Yes.