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

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Message-ID: <20160224222555.GA12073@piout.net>
Date:	Wed, 24 Feb 2016 23:25:55 +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

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.

> +	rtc_tm->tm_sec = bcd2bin(rtc_tm->tm_sec);
> +	rtc_tm->tm_min = bcd2bin(rtc_tm->tm_min);
> +	rtc_tm->tm_hour = bcd2bin(rtc_tm->tm_hour);
> +	rtc_tm->tm_mday = bcd2bin(rtc_tm->tm_mday);
> +	rtc_tm->tm_mon = bcd2bin(rtc_tm->tm_mon) - 1;
> +	rtc_tm->tm_year = bcd2bin(rtc_tm->tm_year);
> +
> +	rtc_tm->tm_year += 100;
> +
> +	dev_dbg(dev, "read time %04d.%02d.%02d %02d:%02d:%02d\n",
> +		1900 + rtc_tm->tm_year, rtc_tm->tm_mon, rtc_tm->tm_mday,
> +		rtc_tm->tm_hour, rtc_tm->tm_min, rtc_tm->tm_sec);
> +
> +	clk_disable(pdata->clk);
> +	return rtc_valid_tm(rtc_tm);
> +}
> +

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