Re: [Linuxptp-users] Can ptp4l be used without phc2sys?

[Brian.Hutchinson--- via Linuxptp-users]

> -----Original Message-----
> From: Irene Kravets <ire...@sapling-inc.com>
> Sent: Tuesday, August 18, 2020 8:35 AM
> To: Richard Cochran <richardcoch...@gmail.com>
> Cc: linuxptp-users@lists.sourceforge.net
> Subject: [SUSPICIOUS] Re: [Linuxptp-users] Can ptp4l be used without
> phc2sys?
> 
> Richard,
> I'd still like to understand why I get synchronized 1PPS signals (with 2 usec
> delay) when I run both ptp4l and phc2sys, but if I only run ptp4l, the 1PPS
> signals are not synchronized?  To clarify, with only ptp4l running, the 1PPS
> signals from master and slave don't drift relative to each other, but the 
> delay
> between the signals is totally random on each boot.  However, if I run ptp4l
> and phc2sync, the delay is always between 2 and 3 usec.  Any ideas on why
> this is happening?
> 
> Thank you,
> Irene.
> 
> -----Original Message-----
> From: Irene Kravets
> Sent: Monday, August 17, 2020 4:55 PM
> To: 'Richard Cochran' <richardcoch...@gmail.com>
> Cc: linuxptp-users@lists.sourceforge.net
> Subject: RE: [Linuxptp-users] Can ptp4l be used without phc2sys?
> 
> Thank you, Richard.  I will follow up with the hardware manufacturer.
> Perhaps it's just a hardware configuration issue.
> 
> -----Original Message-----
> From: Richard Cochran [mailto:richardcoch...@gmail.com]
> Sent: Monday, August 17, 2020 4:51 PM
> To: Irene Kravets <ire...@sapling-inc.com>
> Cc: linuxptp-users@lists.sourceforge.net
> Subject: Re: [Linuxptp-users] Can ptp4l be used without phc2sys?
> 
> On Mon, Aug 17, 2020 at 08:34:29PM +0000, Irene Kravets wrote:
> > Output of phc_ctl eth0:
> >
> > phc_ctl[28.658]:
> > capabilities:
> >   250000000 maximum frequency adjustment (ppb)
> >   0 programable alarms
> >   0 external time stamp channels
> >   0 programmable periodic signals
> 
> Your PHC has zero periodic output signals available.  This means that this
> hardware cannot produce a high quality PPS output.
> 
> >   has pulse per second support
> 
> This a "virtual" PPS time stamp delivered to the kernel.  It can be used by
> phc2sys or ntpd in order to discipline the Linux system time.
> However, it is not a great source of an output PPS signal.  I guess your PPS
> comes from here, and the 2-3 microsecond delay is to be expected.
> 

I also get the exact same results as the OP when I run phc_ctl.

I'm using an IMX8M Mini SoC that has an EMAC with hardware timestamping 
capability as well as a Ethernet switch with hardware timestamping ability too.

I'm using the FEC_ptp driver so I don't understand why phc_ctl is reporting 
zeros.  Do I need to do something in device tree to tell FEC_ptp more about my 
hardware?

Before we made our custom board, we used the NXP IMX8 Mini EVK and had the 
exact same results on that platform too.

Not quite sure what to do about this.

Regards,

Brian

  

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