From mboxrd@z Thu Jan  1 00:00:00 1970
From: will.deacon@arm.com (Will Deacon)
Date: Mon, 25 Nov 2013 18:20:02 +0000
Subject: [PATCH v2] arm64: enable EDAC on arm64
In-Reply-To: <1385154308-31335-1-git-send-email-robherring2@gmail.com>
References: <1385154308-31335-1-git-send-email-robherring2@gmail.com>
Message-ID: <20131125182002.GD28201@mudshark.cambridge.arm.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Fri, Nov 22, 2013 at 09:05:08PM +0000, Rob Herring wrote:
> diff --git a/arch/arm64/include/asm/edac.h b/arch/arm64/include/asm/edac.h
> new file mode 100644
> index 0000000..6d2d262
> --- /dev/null
> +++ b/arch/arm64/include/asm/edac.h
> @@ -0,0 +1,43 @@
> +/*
> + * Copyright 2013 Calxeda, Inc.
> + * Based on PPC version Copyright 2007 MontaVista Software, Inc.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along with
> + * this program.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +#ifndef ASM_EDAC_H
> +#define ASM_EDAC_H
> +/*
> + * ECC atomic, DMA, SMP and interrupt safe scrub function.
> + * Implements the per arch atomic_scrub() that EDAC use for software
> + * ECC scrubbing.  It reads memory and then writes back the original
> + * value, allowing the hardware to detect and correct memory errors.
> + */
> +static inline void atomic_scrub(void *va, u32 size)
> +{
> +	unsigned int *virt_addr = va;
> +	unsigned int i;
> +
> +	for (i = 0; i < size / sizeof(*virt_addr); i++, virt_addr++) {
> +		long result;
> +		unsigned long tmp;
> +
> +		asm volatile("// atomic_scrub\n"
> +		"1:	ldxr	%w0, %2\n"
> +		"	stxr	%w1, %w0, %2\n"
> +		"	cbnz	%w1, 1b"
> +			: "=&r" (result), "=&r" (tmp), "+Q" (*virt_addr)
> +			: : "cc");

You still don't need the "cc" clobber (cbnz doesn't update the flags and,
yes, we have redundant clobbers in our atomic.h which I'll fix...).

Will