[H-GEN] help! problem with real time clock

[Russell Stuart]

On Tue, 2016-12-06 at 10:43 +1000, Peter Robinson wrote:
> If I do a "cold boot" i.e. leave the RPi unplugged for some time (10
> mins seems to be enough in some experiments) then /dev/rtc is not
> created and so the scrip for initializing the rtc and setting the
> time from the rtc fails. If I then do a shutdown and boot within say
> 5 mins then it works fine.
> I have attached dmesg for when it works and doesn't work. I think
> line 281 is where things first go pear shaped
> 
> cold: rtc-ds1307: probe of 1-006f failed with error -5
> warm: rtc-ds1307 1-006f: rtc core: registered mcp7941x as rtc0
> 
> Any thoughts much appreciated.

-5 ie EIO, which translates to "the hardware is misbehaving".  And
apparently that is the usual cause in this case:

https://www.raspberrypi.org/forums/viewtopic.php?f=28&t=58848