linux-kernel - Re: [PATCH 3/3] RTC: Update seconds time programming logic

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20160419223109.GF29844@piout.net>
Date:	Wed, 20 Apr 2016 00:31:09 +0200
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Anurag Kumar Vulisha <anurag.kumar.vulisha@...inx.com>
Cc:	Alessandro Zummo <a.zummo@...ertech.it>,
	soren.brinkmann@...inx.com, Michal Simek <michal.simek@...inx.com>,
	rtc-linux@...glegroups.com, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Punnaiah Choudary Kalluri <punnaia@...inx.com>,
	Anirudha Sarangi <anirudh@...inx.com>,
	Srikanth Vemula <svemula@...inx.com>,
	Anurag Kumar Vulisha <anuragku@...inx.com>
Subject: Re: [PATCH 3/3] RTC: Update seconds time programming logic


Hi,

Please use rtc: zynqmp in your subject line.

On 12/04/2016 at 17:45:46 +0530, Anurag Kumar Vulisha wrote :
> @@ -78,6 +85,17 @@ static int xlnx_rtc_set_time(struct device *dev, struct rtc_time *tm)
>  
>  	writel(new_time, xrtcdev->reg_base + RTC_SET_TM_WR);
>  
> +	/*
> +	 * Clear the rtc interrupt status register after setting the
> +	 * time. During a read_time function, the code should read the
> +	 * RTC_INT_STATUS register and if bit 0 is still 0, it means
> +	 * that one second has not elapsed yet since RTC was set and
> +	 * the current time should be read from SET_TIME_READ register;
> +	 * otherwise, CURRENT_TIME register is read to report the time
> +	 */
> +	writel(RTC_INT_SEC | RTC_INT_ALRM, xrtcdev->reg_base + RTC_INT_STS);

You probably shouldn't clear RTC_INT_ALRM here but it should be done in
the init and when enabling/disabling alarm. Or maybe easier would be to
ignore RTC_INT_ALRM in xlnx_rtc_interrupt when it is not set in
RTC_INT_MASK.

Or, instead of using interrupts, can't you simply read RTC_INT_STS in
xlnx_rtc_read_time()? Is it updated even when the interrupt is not
enabled?

> +	xrtcdev->time_updated = 0;
> +
>  	return 0;
>  }
>  
> @@ -85,7 +103,17 @@ static int xlnx_rtc_read_time(struct device *dev, struct rtc_time *tm)
>  {
>  	struct xlnx_rtc_dev *xrtcdev = dev_get_drvdata(dev);
>  
> -	rtc_time64_to_tm(readl(xrtcdev->reg_base + RTC_CUR_TM), tm);
> +	if (xrtcdev->time_updated == 0) {
> +		/*
> +		 * Time written in SET_TIME_WRITE has not yet updated into
> +		 * the seconds read register, so read the time from the
> +		 * SET_TIME_WRITE instead of CURRENT_TIME register.
> +		 */
> +		rtc_time64_to_tm(readl(xrtcdev->reg_base + RTC_SET_TM_RD), tm);
> +		tm->tm_sec -= 1;
> +	} else {
> +		rtc_time64_to_tm(readl(xrtcdev->reg_base + RTC_CUR_TM), tm);
> +	}
>  
>  	return rtc_valid_tm(tm);
>  }
> @@ -133,6 +161,9 @@ static void xlnx_init_rtc(struct xlnx_rtc_dev *xrtcdev)
>  {
>  	u32 rtc_ctrl;
>  
> +	/* Enable RTC SEC interrupts */
> +	writel(RTC_INT_SEC, xrtcdev->reg_base + RTC_INT_EN);
> +
>  	/* Enable RTC switch to battery when VCC_PSAUX is not available */
>  	rtc_ctrl = readl(xrtcdev->reg_base + RTC_CTRL);
>  	rtc_ctrl |= RTC_BATT_EN;
> @@ -169,8 +200,13 @@ static irqreturn_t xlnx_rtc_interrupt(int irq, void *id)
>  	/* Clear interrupt */
>  	writel(status, xrtcdev->reg_base + RTC_INT_STS);
>  
> -	if (status & RTC_INT_SEC)
> +	if (status & RTC_INT_SEC) {
> +		if (xrtcdev->time_updated == 0) {
> +			/* RTC updated the seconds read register */
> +			xrtcdev->time_updated = 1;
> +		}
>  		rtc_update_irq(xrtcdev->rtc, 1, RTC_IRQF | RTC_UF);
> +	}
>  	if (status & RTC_INT_ALRM)
>  		rtc_update_irq(xrtcdev->rtc, 1, RTC_IRQF | RTC_AF);
>  
> -- 
> 2.1.2
> 

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com