From mboxrd@z Thu Jan 1 00:00:00 1970 From: u.kleine-koenig@pengutronix.de (Uwe =?iso-8859-1?Q?Kleine-K=F6nig?=) Date: Wed, 5 Dec 2012 20:51:34 +0100 Subject: [PATCH] nommu: Enable the strict alignment (CR_A) bit only if ARCH < v6 In-Reply-To: <20121203174617.GL20074@mudshark.cambridge.arm.com> References: <1354187042-28568-1-git-send-email-armando.visconti@st.com> <50BCD6DB.2030200@st.com> <20121203172553.GC14363@n2100.arm.linux.org.uk> <20121203174617.GL20074@mudshark.cambridge.arm.com> Message-ID: <20121205195134.GD3384@pengutronix.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hello, On Mon, Dec 03, 2012 at 05:46:17PM +0000, Will Deacon wrote: > On Mon, Dec 03, 2012 at 05:25:53PM +0000, Russell King - ARM Linux wrote: > > On Mon, Dec 03, 2012 at 05:44:11PM +0100, Armando Visconti wrote: > > > On 11/29/2012 12:04 PM, Armando VISCONTI wrote: > > >> This patch keeps disabled the strict alignment CP15 bit for > > >> all armv6 and armv7 processor without the mmu. This behaviour > > >> is now same as in the mmu case. > > >> > > >> Signed-off-by: Armando Visconti > > >> --- > > >> arch/arm/kernel/head-nommu.S | 2 +- > > >> 1 files changed, 1 insertions(+), 1 deletions(-) > > >> > > >> diff --git a/arch/arm/kernel/head-nommu.S b/arch/arm/kernel/head-nommu.S > > >> index 278cfc1..2c228a0 100644 > > >> --- a/arch/arm/kernel/head-nommu.S > > >> +++ b/arch/arm/kernel/head-nommu.S > > >> @@ -68,7 +68,7 @@ __after_proc_init: > > >> * CP15 system control register value returned in r0 from > > >> * the CPU init function. > > >> */ > > >> -#ifdef CONFIG_ALIGNMENT_TRAP > > >> +#if defined(CONFIG_ALIGNMENT_TRAP)&& __LINUX_ARM_ARCH__< 6 > > >> orr r0, r0, #CR_A > > >> #else > > >> bic r0, r0, #CR_A > > > > > > Any feedback on this simple patch? > > > > Well, it brings the nommu version into line with the mmu version, so > > it's sensible. Please put it in the patch system, thanks. > > In which case, I'll definitely dust-off the patches to prevent unaligned > accesses to strongly-ordered memory because that results in good ol' > UNPREDICTABLE behaviour. > > I think Uwe also requires some of the stuff there for his M3 port. I didn't check more context than available in the patch and I also didn't double-check the M3-docs, but AFAIK the M3 doesn't have a cp15 and I noopt this code out. Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-K?nig | Industrial Linux Solutions | http://www.pengutronix.de/ |