Re: [Linuxptp-users] AM571x linuxptp support

[Richard C. <ric...@gm...>]

On Sat, Nov 19, 2016 at 11:40:03AM -0500, Dale Smith wrote:
> Interesting.  Do you think it's possible to rewrite the driver to
> use whatever HW support is available?  Or is the HW so broken that
> they had to do it in SW?

The HW PLLs on the am335x are not stable, and so when you dial a
non-zero frequency adjustment, the clock goes bonkers.  There is no SW
work around that I am aware of.

> Yeah, if you can't wiggle an I/o pin precisely based of the 1588
> clock, what's the point of the clock?

Well, you can synchronize this PHC reasonably well via PTP, and then
use phc2sys to get the system time globally correct to within a few
microseconds, so it is not totally useless.  but you are right, it is
a shame that this HW unit is so poorly designed.

Thanks,
Richard