[RFC] Prohibit ioremap() on kernel managed RAM
George G. Davis
gdavis at mvista.com
Fri Apr 30 12:33:56 EDT 2010
On Fri, Apr 23, 2010 at 03:40:58PM +0100, Russell King wrote:
> > Above change is necessary but what an alternative approach is for this.
> > There are many use case where ioremap* is needed.
> This is a very difficult issue to answer; the only way we can safely
> remap RAM with different attributes is if we disable the existing
> mappings - but since we create those with 1MB sections, that's far
> from easy to achieve.
> I think a viable safe solution is to set aside some RAM at boot (which
> the kernel doesn't manage at all) and then use ioremap on that; that
> approach will still work with this patch in place.
So cases such as the omapfb driver which use reserve_bootmem() (in
arch/arm/plat-omap/fb.c) and then later use ioremap_wc() to remap
reserved memory (in drivers/video/omap2/omapfb/omapfb-main.c)
will no longer work with this change.
Is that correct?
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