linux-kernel - Re: [PATCH v3] ARM: at91: fix startup rtc irq mask for sam9g25 and sam9g35 SoCs

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Date:	Fri, 9 May 2014 15:03:11 +0200
From:	Nicolas Ferre <nicolas.ferre@...el.com>
To:	Boris BREZILLON <boris.brezillon@...e-electrons.com>
CC:	Bryan Evenson <bevenson@...inkcorp.com>,
	Andrew Victor <linux@...im.org.za>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>,
	Mark Roszko <mark.roszko@...il.com>,
	"Johan Hovold" <jhovold@...il.com>,
	Douglas Gilbert <dgilbert@...erlog.com>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	<stable@...r.kernel.org>
Subject: Re: [PATCH v3] ARM: at91: fix startup rtc irq mask for sam9g25 and
 sam9g35 SoCs

On 09/05/2014 13:01, Boris BREZILLON :
> The sam9g25 and sam9g35 have the following errata:

Cf. below...

> "RTC: Interrupt Mask Register cannot be used
>  Interrupt Mask Register read always returns 0."
> 
> Hence we should not rely on what IMR claims about already masked irqs
> and just disable all the IRQs.
> 
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: <stable@...r.kernel.org> # v3.10+
> Signed-off-by: Boris BREZILLON <boris.brezillon@...e-electrons.com>
> ---
> Hello,
> 
> Sorry for the noise, I just forgot to remove the mask variable in my
> previous version.
> 
> Best Regards,
> 
> Boris
> 
> Changes since v2:
> - removed unused variable 'mask'
> Changes since v1:
> - use a macro to define IRQs bitmask
> - read IMR register to ensure the write to IDR has been flushed
> - quote atmel's datasheet errata in commit message
> - comment the code to describe why we're not using IMR to disable
>   the interrupts
> 
>  arch/arm/mach-at91/sysirq_mask.c | 22 +++++++++++++---------
>  1 file changed, 13 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/arm/mach-at91/sysirq_mask.c b/arch/arm/mach-at91/sysirq_mask.c
> index 2ba694f..1527dda 100644
> --- a/arch/arm/mach-at91/sysirq_mask.c
> +++ b/arch/arm/mach-at91/sysirq_mask.c
> @@ -25,24 +25,28 @@
>  
>  #include "generic.h"
>  
> -#define AT91_RTC_IDR	0x24	/* Interrupt Disable Register */
> -#define AT91_RTC_IMR	0x28	/* Interrupt Mask Register */
> +#define AT91_RTC_IDR		0x24	/* Interrupt Disable Register */
> +#define AT91_RTC_IMR		0x28	/* Interrupt Mask Register */
> +#define AT91_RTC_IRQ_MASK	0x1f	/* Available IRQs mask */
>  
>  void __init at91_sysirq_mask_rtc(u32 rtc_base)
>  {
>  	void __iomem *base;
> -	u32 mask;
>  
>  	base = ioremap(rtc_base, 64);
>  	if (!base)
>  		return;
>  
> -	mask = readl_relaxed(base + AT91_RTC_IMR);
> -	if (mask) {
> -		pr_info("AT91: Disabling rtc irq\n");
> -		writel_relaxed(mask, base + AT91_RTC_IDR);
> -		(void)readl_relaxed(base + AT91_RTC_IMR);	/* flush */
> -	}
> +	/*
> +	 * The sam9g25 and sam9g35 have the following errata:

Actually all chips in what we call the "5 series" or "sam9x5" (sam9g15,
sam9g25, sam9x25, sam9g35 and sam9x35). And... no, the sam9g45 is not
part of that series ;-)

> +	 * "RTC: Interrupt Mask Register cannot be used
> +	 *  Interrupt Mask Register read always returns 0."
> +	 *
> +	 * Hence we're not relying on IMR values to disable
> +	 * interrupts.
> +	 */
> +	writel_relaxed(AT91_RTC_IRQ_MASK, base + AT91_RTC_IDR);
> +	(void)readl_relaxed(base + AT91_RTC_IMR);	/* flush */
>  
>  	iounmap(base);
>  }

Okay for me (maybe change the comment as it can puzzle some users):

Acked-by: Nicolas Ferre <nicolas.ferre@...el.com>

Thanks, bye,
-- 
Nicolas Ferre
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