Re: [Linuxptp-users] Is LinuxPTP and LinuxPPS mutually exclusive?

[<Bri...@L3...>]

> -----Original Message-----
> From: Richard Cochran <ric...@gm...>
> Sent: Friday, February 5, 2021 9:58 PM
> To: Hutchinson, Brian (US) <Bri...@L3...>
> Cc: lin...@li...
> Subject: [EXTERNAL] Re: [Linuxptp-users] Is LinuxPTP and LinuxPPS mutually
> exclusive?
> 
> On Fri, Feb 05, 2021 at 02:45:07PM +0000, Brian.Hutchinson--- via Linuxptp-
> users wrote:
> 
> > ... which got me to thinking, could LinuxPPS be getting in the way of the
> 1PPS we're trying to generate with our fec_ptp imx8mm driver?
> 
> No, certainly not.
> 
> > Wondering if CONFIG_PPS should be turned off in kernel if we are doing
> 1PPS with imx8 fec_php driver or is it needed?
> 
> The CONFIG_PPS is selected by PTP, and so you cannot turn it off.
> 
> 	config PTP_1588_CLOCK
> 		tristate "PTP clock support"
> 		depends on NET && POSIX_TIMERS
> 		select PPS
> 
> The reason for this is that some PTP Hardware Clock drivers generate events
> for the PPS sub-system.  However these are "software" time stamps and are
> totally unrelated to actual "hardware" output signals.

Good to know.

> 
> I'm not familiar with the IMX's FEC hardware, but IIRC it actually does not
> support proper periodic output signals at all.  I could be wrong, though.

Yeah, it is a funky timer arrangement that results in the jitter I believe everyone (including me) complains about.

Regards,

Brian

  

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