Using an external RTC in BBGG

[jose...@gmail.com]

Hi,

I have a custom Cape that has a PCF2129 RTC chip.

I've set a device tree overlay like this:

&{/} {

aliases {

rtc0 = &extrtc;

rtc1 = "/ocp/rtc@44e3e000";

};

};

&i2c1 {

extrtc: pcf2129@51 {

compatible = "nxp,pcf2129";

reg = <0x51>;

};

}

and this setup works fine in a BB Green Wireless:

debian@bbgw:~$ dmesg | grep rtc

[    1.032100] omap_rtc 44e3e000.rtc: already running

[    1.032598] omap_rtc 44e3e000.rtc: registered as rtc1

[    1.133896] rtc-pcf2127-i2c 1-0051: rtc core: registered rtc-pcf2127-i2c as rtc0

[    1.140557] rtc-pcf2127-i2c 1-0051: setting system clock to 2020-09-25 15:27:03 UTC (1601047623)

Nevertheless, trying to use that Cape in a BB Green Gateway (that has another RTC builtin), I'm unable to set the Cape's RTC as default, because it's set as rtc2, instead of rtc0 (using the same overlay file):

 debian@bbgg:~$ dmesg | grep rtc

[    1.084958] omap_rtc 44e3e000.rtc: already running

[    1.085461] omap_rtc 44e3e000.rtc: registered as rtc1

[    1.152108] rtc-ds1307 0-0068: registered as rtc0

[    1.187459] rtc-pcf2127-i2c 1-0051: oscillator stop detected, date/time is not reliable

[    1.187691] rtc-pcf2127-i2c 1-0051: rtc core: registered rtc-pcf2127-i2c as rtc2

[    1.194605] rtc-ds1307 0-0068: setting system clock to 2020-09-25 17:23:30 UTC (1601054610)

Is there any way that I could setup my Cape's DTS file in order the Cape's RTC is used  on a BB Green Gateway?

Best regards,

José Gonçalves

[jose...@gmail.com]

Found it! Just needed to add another alias in the DTS file:

rtc2 = "/ocp/i2c@44e0b000/rtc@68";

and afterwards, my Cape's RTC is used:

debian@bbgg:~$ dmesg | grep rtc

[    1.067904] omap_rtc 44e3e000.rtc: already running

[    1.068392] omap_rtc 44e3e000.rtc: registered as rtc1

[    1.132459] rtc-ds1307 0-0068: registered as rtc2

[    1.172017] rtc-pcf2127-i2c 1-0051: rtc core: registered rtc-pcf2127-i2c as rtc0

[    1.178840] rtc-pcf2127-i2c 1-0051: setting system clock to 2020-09-27 07:40:07 UTC (1601192407)