[PATCH] ARM: fix highmem with VIPT cache and DMA

[Russell King - ARM Linux]

On Fri, May 28, 2010 at 08:45:01PM +0100, Russell King - ARM Linux wrote:
> On Fri, May 28, 2010 at 03:26:21PM -0400, Nicolas Pitre wrote:
> > That is exactly the observed behavior on OMAP and Dove when this patch 
> > is _not_ applied.
> 
> I'm about to test this on my OMAP4 board, which will be a DMA-based test,
> which will be using the same filesystem.

Confirmed - on the OMAP4 board _with_ DMA, this patch fixes a problem
causing various faults in userspace - though it's nowhere near as bad
as the Versatile Express board.

So, we seem to have this behaviour:

- with PIO drivers, with this patch breaks userspace, without fixes userspace
- with DMA drivers, with this patch fixes userspace, without breaks userspace

Note that MMCI does do flush_dcache_page() on PIO read.

Maybe there's something wrong in __flush_dcache_page()?