linux-kernel - Re: [Patch v3 10/11] driver/edac/layerscape

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Date:	Mon, 8 Aug 2016 19:06:52 +0100
From:	Marc Zyngier <marc.zyngier@....com>
To:	York Sun <york.sun@....com>
Cc:	<linux-edac@...r.kernel.org>, <morbidrsa@...il.com>,
	<oss@...error.net>, <stuart.yoder@....com>, <bp@...en8.de>,
	Russell King <linux@...linux.org.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	"Will Deacon" <will.deacon@....com>,
	Doug Thompson <dougthompson@...ssion.com>,
	<mchehab@...nel.org>, James Morse <james.morse@....com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	AKASHI Takahiro <takahiro.akashi@...aro.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [Patch v3 10/11] driver/edac/layerscape_edac: Add Layerscape
 EDAC support

On Thu, 4 Aug 2016 15:58:35 -0700
York Sun <york.sun@....com> wrote:

> Add DDR EDAC for ARM-based compatible controllers. Both big-endian
> and little-endian are supported.
> 
> Signed-off-by: York Sun <york.sun@....com>
> 
> ---
> Change log
>   v3: no change
>   v2: Create new driver using shared DDR object
> 
>  arch/arm64/Kconfig.platforms           |  1 +
>  arch/{arm => arm64}/include/asm/edac.h | 21 +++++------
>  arch/arm64/include/asm/irq.h           |  4 ++
>  drivers/edac/Kconfig                   |  7 ++++
>  drivers/edac/Makefile                  |  3 ++
>  drivers/edac/fsl_ddr_edac.c            |  1 +
>  drivers/edac/layerscape_edac.c         | 67 ++++++++++++++++++++++++++++++++++
>  7 files changed, 92 insertions(+), 12 deletions(-)
>  copy arch/{arm => arm64}/include/asm/edac.h (79%)
>  create mode 100644 drivers/edac/layerscape_edac.c
> 
> diff --git a/arch/arm64/Kconfig.platforms b/arch/arm64/Kconfig.platforms
> index 7ef1d05..185a215 100644
> --- a/arch/arm64/Kconfig.platforms
> +++ b/arch/arm64/Kconfig.platforms
> @@ -41,6 +41,7 @@ config ARCH_EXYNOS
>  
>  config ARCH_LAYERSCAPE
>  	bool "ARMv8 based Freescale Layerscape SoC family"
> +	select EDAC_SUPPORT
>  	help
>  	  This enables support for the Freescale Layerscape SoC family.
>  
> diff --git a/arch/arm/include/asm/edac.h b/arch/arm64/include/asm/edac.h
> similarity index 79%
> copy from arch/arm/include/asm/edac.h
> copy to arch/arm64/include/asm/edac.h
> index 5189fa8..36a226c 100644
> --- a/arch/arm/include/asm/edac.h
> +++ b/arch/arm64/include/asm/edac.h
> @@ -18,16 +18,15 @@
>  #define ASM_EDAC_H
>  /*
>   * ECC atomic, DMA, SMP and interrupt safe scrub function.
> - * Implements the per arch edac_atomic_scrub() that EDAC use for software
> + * 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 edac_atomic_scrub(void *va, u32 size)
> +static inline void atomic_scrub(void *va, u32 size)
>  {
> -#if __LINUX_ARM_ARCH__ >= 6
> -	unsigned int *virt_addr = va;
> -	unsigned int temp, temp2;
> +	unsigned long *virt_addr = va;
> +	unsigned long temp;
> +	unsigned int temp2;
>  	unsigned int i;
>  
>  	for (i = 0; i < size / sizeof(*virt_addr); i++, virt_addr++) {
> @@ -35,15 +34,13 @@ static inline void edac_atomic_scrub(void *va, u32 size)
>  		 * so we are interrupt, DMA and SMP safe.
>  		 */
>  		__asm__ __volatile__("\n"
> -			"1:	ldrex	%0, [%2]\n"
> -			"	strex	%1, %0, [%2]\n"
> -			"	teq	%1, #0\n"
> -			"	bne	1b\n"
> +			"1:	ldxr	%0, [%2]\n"
> +			"	stxr	%w1, %0, [%2]\n"
> +			"	cbnz	%w1, 1b\n"

Hiding architecture code in a driver, are we? Hmmm.

Also, how can this be safe if you have non cache-coherent DMA going on?

>  			: "=&r"(temp), "=&r"(temp2)
>  			: "r"(virt_addr)
> -			: "cc");
> +			: "memory");
>  	}
> -#endif
>  }
>  
>  #endif
> diff --git a/arch/arm64/include/asm/irq.h b/arch/arm64/include/asm/irq.h
> index b77197d..d09c008 100644
> --- a/arch/arm64/include/asm/irq.h
> +++ b/arch/arm64/include/asm/irq.h
> @@ -11,6 +11,10 @@
>  #include <asm-generic/irq.h>
>  #include <asm/thread_info.h>
>  
> +#ifndef NO_IRQ
> +#define NO_IRQ	((unsigned int)(-1))
> +#endif

NAK.

NO_IRQ shouldn't exist at all, and if it had to exist, it would have
the value 0. This really is a leftover of a distant past that has no
real relevance on recent architectures.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny.