linux-kernel - Re: [PATCH] ARM: at91: fix rtc irq mask for sam9x5 SoCs

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Date:	Thu, 8 May 2014 17:49:12 +0200
From:	Johan Hovold <johan@...old.com>
To:	Boris BREZILLON <boris.brezillon@...e-electrons.com>
Cc:	Bryan Evenson <bevenson@...inkcorp.com>,
	Andrew Victor <linux@...im.org.za>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM: at91: fix rtc irq mask for sam9x5 SoCs

On Wed, May 07, 2014 at 06:20:49PM +0200, Boris BREZILLON wrote:
> The RTC IMR register is not reliable on sam9x5 SoCs, hence why me have to
> mask all interrupts no matter what IMR claims about already masked irqs.

Crap, I totally forgot about this. Doug reported the problem off-list
back in December, but it got lost somehow. Sorry.

> Signed-off-by: Boris BREZILLON <boris.brezillon@...e-electrons.com>
> Reported-by: Bryan Evenson <bevenson@...inkcorp.com>
> ---
> Hello Bryan,
> 
> Yet another patch for you ;-).
> 
> As usual, could you tell me if it fixes your bug.
> 
> BTW, thanks for your tests.
> 
> Best Regards,
> 
> Boris
> 
>  arch/arm/mach-at91/sysirq_mask.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/arch/arm/mach-at91/sysirq_mask.c b/arch/arm/mach-at91/sysirq_mask.c
> index 2ba694f..eb3d2a5 100644
> --- a/arch/arm/mach-at91/sysirq_mask.c
> +++ b/arch/arm/mach-at91/sysirq_mask.c
> @@ -37,12 +37,7 @@ void __init at91_sysirq_mask_rtc(u32 rtc_base)
>  	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 */
> -	}
> +	writel_relaxed(0x1f, base + AT91_RTC_IDR);

I believe this is the right way to handle this hardware bug (IMR is
always read as 0 on one particular SoC), but please document this in a
comment.

You should also keep the flush (read of IMR) regardless (to make sure
the write has reached the peripheral), and remember to remove the now
unused mask variable.

>  	iounmap(base);
>  }

Thanks,
Johan
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