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
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