Am 19.01.24 um 13:07 schrieb Josua Mayer: > Am 18.01.24 um 17:07 schrieb Russell King (Oracle): >> On Thu, Jan 18, 2024 at 04:01:10PM +0100, Josua Mayer wrote: >>> HummingBoard has two RTCs, first integrated within SoC that can be used to >>> wake up from sleep - and a second on the carrier board including back-up >>> battery which is intended for keeping time during power-off. >>> >>> Add aliases for both, ensuring that the battery-backed clock is primary >>> rtc and used by default during boot for restoring system time. >> Given that the snvs RTC isn't battery backed, should we even be enabling >> that in DT? > In imx6qdl.dtsi it is not disabled. > According to Jon it is useful because it can wake up the soc from sleep, > whereas the external rtc can't. >> Also, have you seen any issues such as: >> >> [ 0.933249] rtc-pcf8523 0-0068: failed to set xtal load capacitance: -11 >> [ 0.933505] rtc-pcf8523: probe of 0-0068 failed with error -11 >> >> which seems to be exhibiting itself on my SolidSense board? > Not on my HummingBoard Gate Rev. 1.4., but indeed on my solidsense > unit too, which is probably same age as yours. > Only tested imx6dl-hummingboard2-emmc-som-v15.dtb, > but solidsense one should make no difference. I was reading control registers 1-3: debian@sr-imx6:~$ sudo i2cget -y -a -f 0 0x68 0x00 0x00 debian@sr-imx6:~$ sudo i2cget -y -a -f 0 0x68 0x01 0x00 debian@sr-imx6:~$ sudo i2cget -y -a -f 0 0x68 0x02 0x04 ^^ This means low voltage on back up battery After a few power-cycles that error went away. Why pcf8523_load_capacitance would ever return EAGAIN I don't see. In any case now that probe succeeded, I read these values: 0x80 0x00 0x04 And consequently when trying to read or write time I receive [ 88.844038] rtc-pcf8523 0-0068: low voltage detected, time is unreliable Apparently all of my HummingBoard-2 / SolidSense have completely drained their backup batteries to 0.1V over the past 4 years while not in use. FYI replacement part is MS621T. Long story short I don't think the EAGAIN during probe is related to adding aliases. HOWEVER imo pcf8523_probe should return an error when pcf8523_load_capacitance fails.
