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Subject: Re: [PATCH v2] rtc: zynqmp: Clear alarm interrupt status before
 interrupt enable
To:     Srinivas Neeli <srinivas.neeli@xilinx.com>, a.zummo@towertech.it,
        alexandre.belloni@bootlin.com, michal.simek@xilinx.com,
        sgoud@xilinx.com, shubhraj@xilinx.com
Cc:     linux-rtc@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, git@xilinx.com
References: <1581503079-387-1-git-send-email-srinivas.neeli@xilinx.com>
From:   Michal Simek <michal.simek@xilinx.com>
Message-ID: <efe5e4e9-5c4b-fbbf-b333-b8bcaed82ada@xilinx.com>
Date:   Wed, 12 Feb 2020 11:48:46 +0100
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On 12. 02. 20 11:24, Srinivas Neeli wrote:
> Fix multiple occurring interrupts for alarm interrupt. RTC module doesn't
> clear the alarm interrupt status bit immediately after the interrupt is
> triggered.This is due to the sticky nature of the alarm interrupt status
> register. The alarm interrupt status register can be cleared only after
> the second counter outruns the set alarm value. To fix multiple spurious
> interrupts, disable alarm interrupt in the handler and clear the status
> bit before enabling the alarm interrupt.
> 
> Fixes: 11143c19eb57 ("rtc: add xilinx zynqmp rtc driver")
> Signed-off-by: Srinivas Neeli <srinivas.neeli@xilinx.com>
> ---
> Changes in V2:
> Addressed Michal Simek comments
>  - Removed new line in declartion part.
>  - Added new line before return.
> ---
>  drivers/rtc/rtc-zynqmp.c | 27 +++++++++++++++++++++++----
>  1 file changed, 23 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/rtc/rtc-zynqmp.c b/drivers/rtc/rtc-zynqmp.c
> index 5786866c09e9..4b1077e2f826 100644
> --- a/drivers/rtc/rtc-zynqmp.c
> +++ b/drivers/rtc/rtc-zynqmp.c
> @@ -38,6 +38,8 @@
>  
>  #define RTC_CALIB_DEF		0x198233
>  #define RTC_CALIB_MASK		0x1FFFFF
> +#define RTC_ALRM_MASK          BIT(1)
> +#define RTC_MSEC               1000
>  
>  struct xlnx_rtc_dev {
>  	struct rtc_device	*rtc;
> @@ -123,11 +125,28 @@ static int xlnx_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
>  static int xlnx_rtc_alarm_irq_enable(struct device *dev, u32 enabled)
>  {
>  	struct xlnx_rtc_dev *xrtcdev = dev_get_drvdata(dev);
> +	unsigned int status;
> +	ulong timeout;
> +
> +	timeout = jiffies + msecs_to_jiffies(RTC_MSEC);
> +
> +	if (enabled) {
> +		while (1) {
> +			status = readl(xrtcdev->reg_base + RTC_INT_STS);
> +			if (!((status & RTC_ALRM_MASK) == RTC_ALRM_MASK))
> +				break;
> +
> +			if (time_after_eq(jiffies, timeout)) {
> +				dev_err(dev, "Time out occur, while clearing alarm status bit\n");
> +				return -ETIMEDOUT;
> +			}
> +			writel(RTC_INT_ALRM, xrtcdev->reg_base + RTC_INT_STS);
> +		}
>  
> -	if (enabled)
>  		writel(RTC_INT_ALRM, xrtcdev->reg_base + RTC_INT_EN);
> -	else
> +	} else {
>  		writel(RTC_INT_ALRM, xrtcdev->reg_base + RTC_INT_DIS);
> +	}
>  
>  	return 0;
>  }
> @@ -183,8 +202,8 @@ static irqreturn_t xlnx_rtc_interrupt(int irq, void *id)
>  	if (!(status & (RTC_INT_SEC | RTC_INT_ALRM)))
>  		return IRQ_NONE;
>  
> -	/* Clear RTC_INT_ALRM interrupt only */
> -	writel(RTC_INT_ALRM, xrtcdev->reg_base + RTC_INT_STS);
> +	/* Disable RTC_INT_ALRM interrupt only */
> +	writel(RTC_INT_ALRM, xrtcdev->reg_base + RTC_INT_DIS);
>  
>  	if (status & RTC_INT_ALRM)
>  		rtc_update_irq(xrtcdev->rtc, 1, RTC_IRQF | RTC_AF);
> 

Acked-by: Michal Simek <michal.simek@xilinx.com>

Thanks,
Michal