[PATCH 3/4] include asm-mips add missing edac h file

[PATCH 3/4] include asm-mips add missing edac h file

[dougthompson]

From:	Doug Thompson <dougthompson@xmission.h>

EDAC has a foundation to perform software memory scrubbing, but it
requires a per architecture (atomic_scrub) function for performing an atomic
update operation.  Under X86, this is done with a 

lock:  add  [addr],0

in the file asm-x86/edac.h

This patch provides the MIPS arch with that atomic function, atomic_scrub() in

asm-mips/edac.h

Cc:             Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc:		Ralf Baechle <ralf@linux-mips.org>
Signed-off-by:	Doug Thompson <dougthompson@xmission.com>
---
 edac.h |   35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

Index: linux-2.6.23-rc1/include/asm-mips/edac.h
===================================================================
--- /dev/null
+++ linux-2.6.23-rc1/include/asm-mips/edac.h
@@ -0,0 +1,35 @@
+#ifndef ASM_EDAC_H
+#define ASM_EDAC_H
+
+/* ECC atomic, DMA, SMP and interrupt safe scrub function */
+
+static __inline__ void atomic_scrub(void *va, u32 size)
+{
+	unsigned long *virt_addr = va;
+	unsigned long temp;
+	u32 i;
+
+	for (i = 0; i < size / sizeof(unsigned long); i++, virt_addr++) {
+
+		/*
+		 * Very carefully read and write to memory atomically
+		 * so we are interrupt, DMA and SMP safe.
+		 *
+		 * Intel: asm("lock; addl $0, %0"::"m"(*virt_addr));
+		 */
+
+		__asm__ __volatile__ (
+		"       .set    mips3                                   \n"
+		"1:     ll      %0, %1          # atomic_add            \n"
+		"       ll      %0, %1          # atomic_add            \n"
+		"       addu    %0, $0                                  \n"
+		"       sc      %0, %1                                  \n"
+		"       beqz    %0, 1b                                  \n"
+		"       .set    mips0                                   \n"
+		: "=&r" (temp), "=m" (*virt_addr)
+		: "m" (*virt_addr));
+
+	}
+}
+
+#endif

Re: [PATCH 3/4] include asm-mips add missing edac h file

[Andrew Morton]

On Wed, 25 Jul 2007 14:55:01 -0600 dougthompson@xmission.com wrote:

> --- /dev/null
> +++ linux-2.6.23-rc1/include/asm-mips/edac.h
> @@ -0,0 +1,35 @@
> +#ifndef ASM_EDAC_H
> +#define ASM_EDAC_H
> +
> +/* ECC atomic, DMA, SMP and interrupt safe scrub function */
> +
> +static __inline__ void atomic_scrub(void *va, u32 size)

Please don't use __inline__ or __inline.  Good old "inline" will do.

<cc's the checkpatch maintainer>

<edits the diff>

> +{
> +	unsigned long *virt_addr = va;
> +	unsigned long temp;
> +	u32 i;
> +
> +	for (i = 0; i < size / sizeof(unsigned long); i++, virt_addr++) {
> +
> +		/*
> +		 * Very carefully read and write to memory atomically
> +		 * so we are interrupt, DMA and SMP safe.
> +		 *
> +		 * Intel: asm("lock; addl $0, %0"::"m"(*virt_addr));
> +		 */
> +
> +		__asm__ __volatile__ (
> +		"       .set    mips3                                   \n"
> +		"1:     ll      %0, %1          # atomic_add            \n"
> +		"       ll      %0, %1          # atomic_add            \n"
> +		"       addu    %0, $0                                  \n"
> +		"       sc      %0, %1                                  \n"
> +		"       beqz    %0, 1b                                  \n"
> +		"       .set    mips0                                   \n"
> +		: "=&r" (temp), "=m" (*virt_addr)
> +		: "m" (*virt_addr));
> +
> +	}
> +}

hm, I'd have thought that we could us plain old atomic_add() for this.

Re: [PATCH 3/4] include asm-mips add missing edac h file

[Doug Thompson]

--- Andrew Morton <akpm@linux-foundation.org> wrote:

> On Wed, 25 Jul 2007 14:55:01 -0600 dougthompson@xmission.com wrote:
> 
> > --- /dev/null
> > +++ linux-2.6.23-rc1/include/asm-mips/edac.h
> > @@ -0,0 +1,35 @@
> > +#ifndef ASM_EDAC_H
> > +#define ASM_EDAC_H
> > +
> > +/* ECC atomic, DMA, SMP and interrupt safe scrub function */
> > +
> > +static __inline__ void atomic_scrub(void *va, u32 size)
> 
> Please don't use __inline__ or __inline.  Good old "inline" will do.

ok, thanks.

I have to admit, since I don't know MIPS assembly, the guys at Sicortex.com developed
this function.

> 
> <cc's the checkpatch maintainer>
> 
> <edits the diff>

thanks

> 
> > +{
> > +	unsigned long *virt_addr = va;
> > +	unsigned long temp;
> > +	u32 i;
> > +
> > +	for (i = 0; i < size / sizeof(unsigned long); i++, virt_addr++) {
> > +
> > +		/*
> > +		 * Very carefully read and write to memory atomically
> > +		 * so we are interrupt, DMA and SMP safe.
> > +		 *
> > +		 * Intel: asm("lock; addl $0, %0"::"m"(*virt_addr));
> > +		 */
> > +
> > +		__asm__ __volatile__ (
> > +		"       .set    mips3                                   \n"
> > +		"1:     ll      %0, %1          # atomic_add            \n"
> > +		"       ll      %0, %1          # atomic_add            \n"
> > +		"       addu    %0, $0                                  \n"
> > +		"       sc      %0, %1                                  \n"
> > +		"       beqz    %0, 1b                                  \n"
> > +		"       .set    mips0                                   \n"
> > +		: "=&r" (temp), "=m" (*virt_addr)
> > +		: "m" (*virt_addr));
> > +
> > +	}
> > +}
> 
> hm, I'd have thought that we could us plain old atomic_add() for this.

This code is used as a primitive to perform software memory scrubbing.

We (many people as I remember) had a discussion a couple of years ago on lkml on this, 
so this is where this implementation pattern came from.

It might be that your thought just could be correct now after some more research.

doug t