RTC issue

RTC issue

[JH]

Hi,

I built Yocto iMX6ULL image on Zeus kernel 4.19, but I have following
RTC errors:

[ 3494.446265] rtc rtc0: Timeout trying to get valid LPSRT Counter read
[ 4190.088406] rtc rtc0: Timeout trying to get valid LPSRT Counter read
[ 4885.740595] rtc rtc0: Timeout trying to get valid LPSRT Counter read

I measured iMX6ULL RTC_XTALI and RTC_XTALO signals connecting to a
32.768 kHz 90 kΩ ESR crystal, all good, not sure if it is caused by
kernel or Yocto build.

Someone suggested that I should remove the external RTC, the rationale
is that Linux is not really a real time OS, there is no battery for
supporting RTC. Appreciate your comments.

My apology if it is an off topic.

Thank you.

Kind regards,

- jupiter

Re: [yocto] RTC issue

[Matthias Klein]

Hello jupiter,

I have seen the same message on an i.MX6S7 (https://www.karo-electronics.com/fileadmin/download/Datasheets/TX6S-Datasheet.pdf) with kernel 5.10 (in a dunfell Yocto after I upgraded from kernel 4.14).

Since we use an external RTC on the I2C bus, I disabled the internal RTC ("snvs_rtc") in the device tree, and did not analyze the problem further.

I think it is a kernel problem, since in my case the Yocto version has not changed.

Please inform me if you find out something.

Many greetings,
Matthias

Re: [yocto] RTC issue

[JH]

Hello Matthias,

Thanks for your kind response.

> I have seen the same message on an i.MX6S7
> (https://www.karo-electronics.com/fileadmin/download/Datasheets/TX6S-Datasheet.pdf)
> with kernel 5.10 (in a dunfell Yocto after I upgraded from kernel 4.14).
>
> Since we use an external RTC on the I2C bus, I disabled the internal RTC
> ("snvs_rtc") in the device tree, and did not analyze the problem further.

How did you disable snvs_rtc? My device tree to include imx6ull.dtsi
which don't have snvs_rtc, only has snvs-rtc-lp, so I added status =
"disabled"; to the snvs-rtc-lp node:

snvs-rtc-lp {
    compatible = "fsl,sec-v4.0-mon-rtc-lp";
     regmap = <0x16>;
     offset = <0x34>;
    status = "disabled";
}

that must be wrong, it crashed in kernel booting.

[    9.478754] ---[ end trace dc624b5857965e18 ]---
[    9.483962] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0b
[    9.483962]
[    9.493223] ---[ end Kernel panic - not syncing: Attempted to kill init! exib
[    9.493223]  ]---


Thank you.

Kind regards,

- jupiter

Re: [yocto] RTC issue

[Matthias Klein]

Hello Jupiter,

>How did you disable snvs_rtc? My device tree to include imx6ull.dtsi which don't have snvs_rtc, only has snvs-rtc-lp, so I added status = "disabled"; to the snvs-rtc-lp node:
>
>snvs-rtc-lp {
>    compatible = "fsl,sec-v4.0-mon-rtc-lp";
>     regmap = <0x16>;
>     offset = <0x34>;
>    status = "disabled";
>}
>
>that must be wrong, it crashed in kernel booting.

I only added status = "disabled": https://github.com/optimeas/linux-tx6-5.10/blob/tx6-5.10/arch/arm/boot/dts/imx6dl-tx6s-8035-smartmini-v2p3.dts#L77

Best regards,
Matthias