[RESEND PATCH v4] ARM: at91: fix at91_sysirq_mask_rtc for sam9x5 SoCs

[Johan Hovold]

On Fri, May 09, 2014 at 04:43:30PM +0200, Boris BREZILLON wrote:
> sam9x5 SoCs have the following errata:
> "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 IRQs.
> 
> Cc: Andrew Morton <akpm at linux-foundation.org>
> Cc: <stable at vger.kernel.org> # v3.10+
> Signed-off-by: Boris BREZILLON <boris.brezillon at free-electrons.com>
> Acked-by: Nicolas Ferre <nicolas.ferre at atmel.com>

Reviewed-by: Johan Hovold <jhovold at gmail.com>

Looks good, but for the future: Why do you break the comment lines you
added at column 60?

Thanks,
Johan

> ---
> Hello,
> 
> Again, sorry for the noise, but I forgot to add Nicolas' ack and to keep
> Andrew and the stable ML in cc.
> 
> Best Regards,
> 
> Boris
> 
> Changes since v3:
> - fix commit message and comment
> 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..f8bc351 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 */
> -	}
> +	/*
> +	 * sam9x5 SoCs have the following errata:
> +	 * "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);
>  }