[Letux-kernel] Where does RTC actually work

Andreas Kemnade andreas at kemnade.info
Mon Jan 30 20:40:36 CET 2017


Hi,

On Mon, 30 Jan 2017 19:28:58 +0100
"H. Nikolaus Schaller" <hns at goldelico.com> wrote:

> 
> > Am 30.01.2017 um 19:16 schrieb Andreas Kemnade
> > <andreas at kemnade.info>:
> > 
> > Hi,
> > 
> > I cannot remember when I saw a device with a working RTC last time.
> > On my semi-broken GTA04A4 it is kept across reboots at least with
> > 3.7. Not when the battery is even removed for a short time.
> > On the fresh GTA04A5 board it is not even kept across reboots with
> > 4.10rc-4.
> > 
> > So what are the known-good combinations (kernel + device)?
> 
> I think on the 3.12 kernel it was tested and did work.
> 
I just tested what I have without bulding or copying stuff around...

I tested further and narrow it a bit:
on my gta04a4 (with old uboot) time is kept with 4.7.0 across powerdown
(not battery removal)
root at gta04:~# for i in 1 2 3 4 5 6 7 8 ; do
cat /sys/bus/iio/devices/iio\:device1/in_voltage9_input  ; sleep 1 ;
done 3030 2863
3431
3466
3382
2727
3316
3171

And the backup battery stuff looks somewhat broken (probably hardware).
The same kernel + same modules on a letux3704 (with new uboot):
Voltages stable,
clock does not survive reboots.

Verdict:
1. gta04a4 backup capacitor is broken
2. new uboot conflicts with rtc.

Regards,
Andreas
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