From mboxrd@z Thu Jan 1 00:00:00 1970 From: nicolas.pitre@linaro.org (Nicolas Pitre) Date: Thu, 11 Oct 2012 11:58:15 -0400 (EDT) Subject: [PATCH] ARM: decompressor: clear SCTLR.A bit for v7 cores In-Reply-To: <20121011135925.GR4625@n2100.arm.linux.org.uk> References: <1349959402-24164-1-git-send-email-robherring2@gmail.com> <20121011130955.GP4625@n2100.arm.linux.org.uk> <5076CA43.9070503@gmail.com> <20121011135925.GR4625@n2100.arm.linux.org.uk> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, 11 Oct 2012, Russell King - ARM Linux wrote: > On Thu, Oct 11, 2012 at 08:31:47AM -0500, Rob Herring wrote: > > This only affects v7 cores. It should not vary for v7 cores as unaligned > > access is a required feature. So how is it going to vary on v7 CPUs? > > We've got bigger problems if there are v7 cores that don't handle > > unaligned accesses. > > Oh, and this gives me a third reason to NAK this patch. Why only ensure > that the A bit is clear for v7 CPUs? Why not v6, v5, v4 too? Why does > ARMv7 get this special treatment? As I said, gcc knows that ARMv7 can perform word sized accesses even with misaligned pointers. So when it is passed a pointer marked with the packed attribute, it will generate a series of byte accesses when compiling for anything but ARMv7, and use a single ldr or str when compiling for ARMv7. Nicolas