[ntp:questions] Timing issue with Linux and kernel PPS?

Miroslav Lichvar mlichvar at redhat.com
Mon Nov 19 09:44:04 UTC 2012

On Mon, Nov 19, 2012 at 09:02:12AM +0000, David Taylor wrote:
> On 18/11/2012 15:20, Uwe Klein wrote:
> >what happens if you "insmod pps_ldisc" into the "not ready" system?
> (1) I get Error: could not load pps_ldisc module: No such file or directory

insmod needs full path to the module, it's better to call "modprobe pps_ldisc".

> I looked at the article you referenced, but in this case the
> Raspberry Pi is not using the DCD line, but a separate GPIO pin.
> lsmod shows pps_gpio as present.

>From the original post it seems you have two pps devices, one for gpio
and the other for ldisc which is created two minutes later (some USB

Do you see two /dev/pps* devices and are you sure ntpd is using the
gpio one? Perhaps there is an ordering problem?

Miroslav Lichvar

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