[PATCH 1/4] ARM: Change the mandatory barriers implementation

[linux@arm.linux.org.uk (Russell King - ARM Linux)]

On Tue, Feb 23, 2010 at 05:05:31PM +0530, Shilimkar, Santosh wrote:
> OMAP3 and family would be ok with this much needed mandatory barriers
> but for OMAP4, we need platform specified barriers as you mentioned. Will
> have a look at this series and do some testing on OMAP4. Will send
> a follow up patch then.

Wait for v2 - it introduces barriers onto the older CPUs which do not
need it, and therefore is definitely not right.

Eg, ARMv4 CPUs don't need the drain-write-buffer instruction for mb()
and wmb() - we have no relaxed behaviours on those CPUs, so this is
pointless.  As I also pointed out, it breaks ARMv3 because the drain-
write-buffer instruction there is an undefined instruction.

Plus, non-coherent Xscale has the same requirements as ARMv4, so getting
rid of the arch_is_coherent() stuff was completely wrong.

Basically, the patch is not suitable as it currently stands, and is in
need of rework.