Re: Cubox i4pro real time clock(s)

[Karsten Merker <merker@debian.org>]

On Fri, Apr 10, 2015 at 03:07:31AM -0700, Rick Thomas wrote:

> Whenever I reset my cubox-i4Pro by disconnecting the power
> plug, the hardware real-time-clock gets reset to midnight UTC,
> Dec 31, 1970.  Even though the SolidRun literature says that
> the i4Pro has a battery backed RTC.
> 
> A bit of googling reveals that this is related to the following
> fact (Quoted from the SolidRun forums)
> 
> > There are two RTC inside CuBox-i 
> > 1. One connected to the SNVS rail (internal i.MX6) which is
> > not battery backed and typically goes to /dev/rtc0
> > 2. Second is NXP PFC8523 based and that one has battery
> > backup (/dev/rtc1)
[...]
> Curiously, when I look at the Debian Jessie system running on
> the box, I find that there is only one /dev/rtc* device, and
> that seems to be associated with the SNVS clock.  The PFC8523
> clock is not available…
> 
> Checking /boot/config-3.16.0-4-armmp, I see what I think is an
> explanation, because
> 
> > # CONFIG_RTC_DRV_PCF8523 is not set
> 
> and
> 
> > CONFIG_RTC_DRV_SNVS=y
> 
> Other Linux systems (e.g. Arch) appear (according to the above
> mentioned googling) to have their kernel compiled so as to
> provide both /dev/rtc0 attached to the SNVS clock, and
> /dev/rtc1 attached to the PFC8523 clock.
> 
> Would it be possible to configure the default Debian Jessie
> kernel to do the same?

Yes, that should just need enabling the appropriate module.
The device-tree instantiates the pcf8523 clock chip:

&i2c3 {
        pinctrl-names = "default";
        pinctrl-0 = <&pinctrl_cubox_i_i2c3>;

        status = "okay";

        rtc: pcf8523@68 {
                compatible = "nxp,pcf8523";
                reg = <0x68>;
        };
};

So if the module is available, it should be loaded automatically.

Please file a wishlist bug against "Source: linux, Version: 
3.16.7-ckt9-1" so that the kernel maintainers can enable the
module for the next kernel upload.

Regards,
Karsten
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