linux-kernel - Re: [rtc-linux] [PATCH] rtc: mt6397: fix build on some 32bits platforms

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Date:	Thu, 14 May 2015 23:55:04 +0200
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Eddie Huang <eddie.huang@...iatek.com>
Cc:	rtc-linux@...glegroups.com, linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [rtc-linux] [PATCH] rtc: mt6397: fix build on some 32bits
 platforms

Hi,

On 14/05/2015 at 22:51:18 +0200, Alexandre Belloni wrote :
> On some !ARM 32bits platforms, the following compilation error happens
> because of the division on a 64bits value in mtk_rtc_read_time():
> 
> drivers/built-in.o: In function `mtk_rtc_read_time':
> rtc-mt6397.c:(.text+0x265d13f): undefined reference to `__divdi3'
> rtc-mt6397.c:(.text+0x265d150): undefined reference to `__moddi3'
> 
> Use div_s64() as done in rtc_time64_to_tm() to solve that.
> 
> Reported-by: kbuild test robot <fengguang.wu@...el.com>
> Signed-off-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>

I've already pushed that patch to rtc-next to repair the build for i386
and m68k but feel free to comment if you see anything wrong.

> ---
>  drivers/rtc/rtc-mt6397.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/rtc/rtc-mt6397.c b/drivers/rtc/rtc-mt6397.c
> index 8bed852e4961..c0090b698ff3 100644
> --- a/drivers/rtc/rtc-mt6397.c
> +++ b/drivers/rtc/rtc-mt6397.c
> @@ -150,7 +150,7 @@ static int mtk_rtc_read_time(struct device *dev, struct rtc_time *tm)
>  {
>  	time64_t time;
>  	struct mt6397_rtc *rtc = dev_get_drvdata(dev);
> -	int sec, ret;
> +	int days, sec, ret;
>  
>  	do {
>  		ret = __mtk_rtc_read_time(rtc, tm, &sec);
> @@ -171,7 +171,8 @@ static int mtk_rtc_read_time(struct device *dev, struct rtc_time *tm)
>  	/* rtc_tm_to_time64 covert Gregorian date to seconds since
>  	 * 01-01-1970 00:00:00, and this date is Thursday.
>  	 */
> -	tm->tm_wday = (time / 86400 + 4) % 7;
> +	days = div_s64(time, 86400);
> +	tm->tm_wday = (days + 4) % 7;
>  
>  exit:
>  	return ret;
> -- 
> 2.1.4
> 
> -- 
> -- 
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> before submitting a driver.
> --- 
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-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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