On 09/01/2025 16:29:52+0100, Alexandre Mergnat wrote:
> Removing the RTC_MIN_YEAR_OFFSET addition and subtraction has
> introduced a regression.
>
> ~# hwclock -r --verbose
> hwclock from util-linux 2.37.4
> System Time: 1262312013.143552
> Trying to open: /dev/rtc0
> Using the rtc interface to the clock.
> Assuming hardware clock is kept in UTC time.
> Waiting for clock tick...
> hwclock: select() to /dev/rtc0 to wait for clock tick timed out
> ...synchronization failed
>
> Bring back the RTC_MIN_YEAR_OFFSET to fix the RTC.
>
NAK, you'd have to investigate a bit more, I want to get rid of the
RTC_MIN_YEAR_OFFSET insanity.
> Fixes: 34bbdc12d04e ("rtc: mt6359: Add RTC hardware range and add support for start-year")
> Signed-off-by: Alexandre Mergnat <amergnat@xxxxxxxxxxxx>
> ---
> drivers/rtc/rtc-mt6397.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/drivers/rtc/rtc-mt6397.c b/drivers/rtc/rtc-mt6397.c
> index 55e75712edd4..9930b6bdb6ca 100644
> --- a/drivers/rtc/rtc-mt6397.c
> +++ b/drivers/rtc/rtc-mt6397.c
> @@ -96,6 +96,12 @@ static int mtk_rtc_read_time(struct device *dev, struct rtc_time *tm)
> goto exit;
> } while (sec < tm->tm_sec);
>
> + /* HW register use 7 bits to store year data, minus
> + * RTC_MIN_YEAR_OFFSET before write year data to register, and plus
> + * RTC_MIN_YEAR_OFFSET back after read year from register
> + */
> + tm->tm_year += RTC_MIN_YEAR_OFFSET;
> +
> /* HW register start mon/wday from one, but tm_mon/tm_wday start from zero. */
> tm->tm_mon--;
> tm->tm_wday--;
> @@ -110,6 +116,7 @@ static int mtk_rtc_set_time(struct device *dev, struct rtc_time *tm)
> int ret;
> u16 data[RTC_OFFSET_COUNT];
>
> + tm->tm_year -= RTC_MIN_YEAR_OFFSET;
> tm->tm_mon++;
> tm->tm_wday++;
>
> @@ -167,6 +174,7 @@ static int mtk_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alm)
> tm->tm_mon = data[RTC_OFFSET_MTH] & RTC_AL_MTH_MASK;
> tm->tm_year = data[RTC_OFFSET_YEAR] & RTC_AL_YEA_MASK;
>
> + tm->tm_year += RTC_MIN_YEAR_OFFSET;
> tm->tm_mon--;
>
> return 0;
> @@ -182,6 +190,7 @@ static int mtk_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alm)
> int ret;
> u16 data[RTC_OFFSET_COUNT];
>
> + tm->tm_year -= RTC_MIN_YEAR_OFFSET;
> tm->tm_mon++;
>
> mutex_lock(&rtc->lock);
>
> --
> 2.25.1
>
--
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
