possible off-by-one error on month counting in rtc rv8803 driver
Oliver Graute
oliver.graute at gmail.com
Mon Apr 25 14:55:39 CEST 2022
Hello,
I stumbled across the following possible off-by-one error in counting the
month in RTC driver rv8803.
I'am using struct rtc_time to define a EOL date for my U-Boots. So after
this date U-Boot stops booting by reading the RTC before with rtc_get().
I'am using the same EOL code for two different imx boards with different
RTCs and therefore different RTC drivers. On both boards I have set the
same EOL date.
So the EOL Date is 25.09.2022 23:59:59
The board with rv3029 stopps booting on 26.09.2022 0:00:00
The board with rv8803 stopps booting on 26.08.2022 0:00:00
U-Boot Code:
(drivers/rtc/rv3029.c)
v3029_rtc_set()
...
regs[RV3029_W_MONTHS - RV3029_W_SEC] = bin2bcd(tm->tm_mon + 1);
...
rv3029_rtc_get()
...
tm->tm_mon = bcd2bin(regs[RV3029_W_MONTHS - RV3029_W_SEC]) - 1;
...
(drivers/rtc/rv8803.c)
rv8803_rtc_set()
...
buf[RTC_MON_REG_ADDR] = bin2bcd(tm->tm_mon)
...
rv8803_rtc_get()
...
tm->tm_mon = bcd2bin(buf[RTC_MON_REG_ADDR] & 0x1F);
...
I assume that the error is here and increase and decrease by one is also
required here like in the Linux driver code for RTC 8803.
Linux Code:
rv3029_set_time()
...
regs[RV3029_W_MONTHS - RV3029_W_SEC] = bin2bcd(tm->tm_mon + 1);
...
rv3029_read_time()
...
tm->tm_mon = bcd2bin(regs[RV3029_W_MONTHS - RV3029_W_SEC]) - 1;
...
rv8803_set_time()
...
date[RV8803_MONTH] = bin2bcd(tm->tm_mon + 1);
...
rv8803_get_time()
...
tm->tm_mon = bcd2bin(date[RV8803_MONTH] & 0x1f) - 1;
...
Can someone verify and comment on this. Then I would prepare a patch
later on.
Best Regards,
Oliver
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