linux-kernel - Re: [PATCH v2 2/2] rtc: rtc-pic32: Add PIC32 real time clock driver

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Message-ID: <20160225165449.GH12073@piout.net>
Date:	Thu, 25 Feb 2016 17:54:49 +0100
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Joshua Henderson <joshua.henderson@...rochip.com>
Cc:	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	rtc-linux@...glegroups.com
Subject: Re: [PATCH v2 2/2] rtc: rtc-pic32: Add PIC32 real time clock driver

On 25/02/2016 at 09:23:55 -0700, Joshua Henderson wrote :
> On 02/24/2016 03:25 PM, Alexandre Belloni wrote:
> > Hi,
> > 
> > On 19/02/2016 at 11:09:45 -0700, Joshua Henderson wrote :
> >> +static int pic32_rtc_gettime(struct device *dev, struct rtc_time *rtc_tm)
> >> +{
> >> +	struct pic32_rtc_dev *pdata = dev_get_drvdata(dev);
> >> +	void __iomem *base = pdata->reg_base;
> >> +	unsigned int tries = 0;
> >> +
> >> +	clk_enable(pdata->clk);
> >> +
> >> +	do {
> >> +		rtc_tm->tm_hour = readb(base + PIC32_RTCHOUR);
> >> +		rtc_tm->tm_min = readb(base + PIC32_RTCMIN);
> >> +		rtc_tm->tm_mon  = readb(base + PIC32_RTCMON);
> >> +		rtc_tm->tm_mday = readb(base + PIC32_RTCDAY);
> >> +		rtc_tm->tm_year = readb(base + PIC32_RTCYEAR);
> >> +		rtc_tm->tm_sec  = readb(base + PIC32_RTCSEC);
> >> +
> >> +		/*
> >> +		 * The only way to work out whether the system was mid-update
> >> +		 * when we read it is to check the second counter, and if it
> >> +		 * is zero, then we re-try the entire read.
> >> +		 */
> >> +		tries = 1;
> >> +	} while (rtc_tm->tm_sec == 0 && tries < 2);
> >> +
> > 
> > This doesn't seem right. It will wait up to a second as tries will
> > always be less than 2, this is probably not what you want.
> 
> Dang good catch.  When fixed, it will work as expected:
> 
> # hwclock
> tries 1
> Sun Oct 17 19:23:59 2010  0.000000 seconds
> # hwclock
> tries 1
> tries 2
> Sun Oct 17 19:24:00 2010  0.000000 seconds
> # hwclock
> tries 1
> Sun Oct 17 19:24:01 2010  0.000000 seconds
> 

Sure, just send v3, I'll apply it right away ;)


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