Re: ioremap_nocache problem?

[Roman Zippel]

Hi,

On Tue, 23 Jan 2001, Mark Mokryn wrote:

> ioremap_nocache does the following:
> 	return __ioremap(offset, size, _PAGE_PCD);
> 
> However, in drivers/char/mem.c (2.4.0), we see the following:
> 
> 	/* On PPro and successors, PCD alone doesn't always mean 
> 	    uncached because of interactions with the MTRRs. PCD | PWT
> 	    means definitely uncached. */ 
> 	if (boot_cpu_data.x86 > 3)
> 		prot |= _PAGE_PCD | _PAGE_PWT;
> 
> Does this mean ioremap_nocache() may not do the job?

ioremap creates a new mapping that shouldn't interfere with MTRR, whereas
you can map a MTRR mapped area into userspace. But I'm not sure if it's
correct that no flag is set for boot_cpu_data.x86 <= 3...

bye, Roman