From mboxrd@z Thu Jan 1 00:00:00 1970 From: linux@arm.linux.org.uk (Russell King - ARM Linux) Date: Tue, 23 Feb 2010 11:41:16 +0000 Subject: [PATCH 1/4] ARM: Change the mandatory barriers implementation In-Reply-To: References: <20100223110105.11048.8143.stgit@e102109-lin.cambridge.arm.com> Message-ID: <20100223114116.GB10501@n2100.arm.linux.org.uk> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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.