Re: [PATCH] rtc: rzn1: Fix RTC_RD_TIME: Invalid argument

[Alexandre Belloni <alexandre.belloni@bootlin.com>]

Hello,

On 06/07/2022 13:07:56+0100, Biju Das wrote:
> This patch fixes the issue RTC_RD_TIME: Invalid argument with the below
> use case.
> 
> Steps to reproduce:
> ------------------
> date -s "2022-12-31 23:59:55";hwclock -w
> hwclock; sleep 10; hwclock
> 
> Original result:
> ---------------
> Sat Dec 31 23:59:55 UTC 2022
> Sat Dec 31 23:59:56 2022  0.000000 seconds
> hwclock: RTC_RD_TIME: Invalid argument
> 
> Result after the fix:
> --------------------
> Sat Dec 31 23:59:55 UTC 2022
> Sat Dec 31 23:59:56 2022  0.000000 seconds
> Sun Jan  1 00:00:06 2023  0.000000 seconds
> 
> Fixes: deeb4b5393e1 ("rtc: rzn1: Add new RTC driver")
> Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
> ---
> This patch fix is based on [1]
> [1] https://github.com/renesas-rz/rzn1_linux/blob/rzn1-stable-v4.19/drivers/rtc/rtc-rzn1.c
> ---
>  drivers/rtc/rtc-rzn1.c | 47 ++++++++++++++++++++++++++++--------------
>  1 file changed, 32 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/rtc/rtc-rzn1.c b/drivers/rtc/rtc-rzn1.c
> index ac788799c8e3..0f99b4fd3c4b 100644
> --- a/drivers/rtc/rtc-rzn1.c
> +++ b/drivers/rtc/rtc-rzn1.c
> @@ -88,6 +88,35 @@ static unsigned int rzn1_rtc_tm_to_wday(struct rtc_time *tm)
>  	return (days + 4) % 7;
>  }
>  
> +static void bcd2tm(struct rtc_time *tm)
> +{
> +	tm->tm_sec = bcd2bin(tm->tm_sec);
> +	tm->tm_min = bcd2bin(tm->tm_min);
> +	tm->tm_hour = bcd2bin(tm->tm_hour);
> +	tm->tm_wday = bcd2bin(tm->tm_wday);
> +	tm->tm_mday = bcd2bin(tm->tm_mday);
> +	tm->tm_mon = bcd2bin(tm->tm_mon) - 1;

I guess this is the actual fix, I'm not sure creating the bcd2tm and
tm2bcd functions is useful, it obfuscates more than it helps.


> +	/* epoch == 1900 */
> +	tm->tm_year = bcd2bin(tm->tm_year) + 100;

Is it really the epoch of the RTC?

> +}
> +
> +static int tm2bcd(struct rtc_time *tm)
> +{
> +	if (rtc_valid_tm(tm) != 0)
> +		return -EINVAL;
> +

This will never fail, I'm not sure why you need to check here.

> +	tm->tm_sec = bin2bcd(tm->tm_sec);
> +	tm->tm_min = bin2bcd(tm->tm_min);
> +	tm->tm_hour = bin2bcd(tm->tm_hour);
> +	tm->tm_wday = bin2bcd(rzn1_rtc_tm_to_wday(tm));
> +	tm->tm_mday = bin2bcd(tm->tm_mday);
> +	tm->tm_mon = bin2bcd(tm->tm_mon + 1);
> +	/* epoch == 1900 */
> +	tm->tm_year = bin2bcd(tm->tm_year - 100);
> +
> +	return 0;
> +}
> +
>  static int rzn1_rtc_read_time(struct device *dev, struct rtc_time *tm)
>  {
>  	struct rzn1_rtc *rtc = dev_get_drvdata(dev);
> @@ -106,14 +135,7 @@ static int rzn1_rtc_read_time(struct device *dev, struct rtc_time *tm)
>  	if (tm->tm_sec != secs)
>  		rzn1_rtc_get_time_snapshot(rtc, tm);
>  
> -	tm->tm_sec = bcd2bin(tm->tm_sec);
> -	tm->tm_min = bcd2bin(tm->tm_min);
> -	tm->tm_hour = bcd2bin(tm->tm_hour);
> -	tm->tm_wday = bcd2bin(tm->tm_wday);
> -	tm->tm_mday = bcd2bin(tm->tm_mday);
> -	tm->tm_mon = bcd2bin(tm->tm_mon);
> -	tm->tm_year = bcd2bin(tm->tm_year);
> -
> +	bcd2tm(tm);
>  	return 0;
>  }
>  
> @@ -123,13 +145,8 @@ static int rzn1_rtc_set_time(struct device *dev, struct rtc_time *tm)
>  	u32 val;
>  	int ret;
>  
> -	tm->tm_sec = bin2bcd(tm->tm_sec);
> -	tm->tm_min = bin2bcd(tm->tm_min);
> -	tm->tm_hour = bin2bcd(tm->tm_hour);
> -	tm->tm_wday = bin2bcd(rzn1_rtc_tm_to_wday(tm));
> -	tm->tm_mday = bin2bcd(tm->tm_mday);
> -	tm->tm_mon = bin2bcd(tm->tm_mon);
> -	tm->tm_year = bin2bcd(tm->tm_year);
> +	if (tm2bcd(tm) < 0)
> +		return -EINVAL;
>  
>  	val = readl(rtc->base + RZN1_RTC_CTL2);
>  	if (!(val & RZN1_RTC_CTL2_STOPPED)) {
> -- 
> 2.25.1
> 

-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com