rtc-pcf8563: STOP bit usage during time update?

rtc-pcf8563: STOP bit usage during time update?

[David Müller (ELSOFT AG)]

Hello

According to the example on page 30 of the EPSON datasheet
https://support.epson.biz/td/api/doc_check.php?dl=app_RTC-8564JE&lang=en
for the 8564 version of this chip, the time update sequence is as follows:

- set CTRLSTS1[STOP] bit to 1
- update time registers
- set CTRLSTS1[STOP] bit to 0

The NXP datasheet is not so explicit regarding STOP bit handling.

Nevertheless I don't see any STOP bit related action in the driver:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/rtc/rtc-pcf8563.c?h=v5.14#n244

Am I overlooking or missing something here?

Re: rtc-pcf8563: STOP bit usage during time update?

[Alexandre Belloni]

On 25/09/2021 09:00:00+0200, David Müller (ELSOFT AG) wrote:
> According to the example on page 30 of the EPSON datasheet
> https://support.epson.biz/td/api/doc_check.php?dl=app_RTC-8564JE&lang=en
> for the 8564 version of this chip, the time update sequence is as follows:
> 
> - set CTRLSTS1[STOP] bit to 1
> - update time registers
> - set CTRLSTS1[STOP] bit to 0
> 
> The NXP datasheet is not so explicit regarding STOP bit handling.
> 
> Nevertheless I don't see any STOP bit related action in the driver:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/rtc/rtc-pcf8563.c?h=v5.14#n244
> 
> Am I overlooking or missing something here?

You are not missing anything, the driver is not stopping the clock while
updating it. The hym8563 driver (which is compatible) does it.


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