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Re: [PATCH 4/6] net: ethernet: ti: cpts: add ptp pps support

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On Mon, Nov 28, 2016 at 05:04:26PM -0600, Grygorii Strashko wrote:
> +static cycle_t cpts_cc_ns2cyc(struct cpts *cpts, u64 nsecs)
> +{
> +	cycle_t cyc = (nsecs << cpts->cc.shift) + nsecs;
> +
> +	do_div(cyc, cpts->cc.mult);
> +
> +	return cyc;
> +}

So you set the comparison value once per second, based on cc.mult.
But when the clock is being actively synchronized, user space calls to
clock_adjtimex() will change cc.mult.  This can happen several times
per second, depending on the PTP Sync rate.

In order to produce the PPS edge correctly, you would have to adjust
the comparison value whenever cc.mult changes, but of course this is
unworkable.

So I'll have to say NAK for this patch.

Thanks,
Richard

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[PATCH 0/6] net: ethernet: ti: cpts: update and enable support on keystone 2 socs Grygorii Strashko <grygorii.strashko@ti.com> - 2016-11-29 00:10 +0100
  [PATCH 2/6] net: ethernet: ti: cpts: add support for ext rftclk selection Grygorii Strashko <grygorii.strashko@ti.com> - 2016-11-29 00:10 +0100
    Re: [PATCH 2/6] net: ethernet: ti: cpts: add support for ext rftclk  selection Richard Cochran <richardcochran@gmail.com> - 2016-11-30 11:00 +0100
      Re: [PATCH 2/6] net: ethernet: ti: cpts: add support for ext rftclk  selection Grygorii Strashko <grygorii.strashko@ti.com> - 2016-11-30 18:40 +0100
        Re: [PATCH 2/6] net: ethernet: ti: cpts: add support for ext rftclk  selection Grygorii Strashko <grygorii.strashko@ti.com> - 2016-12-06 20:50 +0100
          Re: [PATCH 2/6] net: ethernet: ti: cpts: add support for ext rftclk  selection Richard Cochran <richardcochran@gmail.com> - 2016-12-06 21:30 +0100
            Re: [PATCH 2/6] net: ethernet: ti: cpts: add support for ext rftclk  selection Grygorii Strashko <grygorii.strashko@ti.com> - 2016-12-06 21:50 +0100
          Re: [PATCH 2/6] net: ethernet: ti: cpts: add support for ext rftclk  selection Stephen Boyd <sboyd@codeaurora.org> - 2016-12-09 01:50 +0100
            Re: [PATCH 2/6] net: ethernet: ti: cpts: add support for ext rftclk  selection Grygorii Strashko <grygorii.strashko@ti.com> - 2016-12-10 00:40 +0100
    Re: [PATCH 2/6] net: ethernet: ti: cpts: add support for ext rftclk  selection Rob Herring <robh@kernel.org> - 2016-12-05 16:00 +0100
  [PATCH 4/6] net: ethernet: ti: cpts: add ptp pps support Grygorii Strashko <grygorii.strashko@ti.com> - 2016-11-29 00:10 +0100
    Re: [PATCH 4/6] net: ethernet: ti: cpts: add ptp pps support Richard Cochran <richardcochran@gmail.com> - 2016-11-30 11:10 +0100
      Re: [PATCH 4/6] net: ethernet: ti: cpts: add ptp pps support Richard Cochran <richardcochran@gmail.com> - 2016-12-06 19:10 +0100
        Re: [PATCH 4/6] net: ethernet: ti: cpts: add ptp pps support Grygorii Strashko <grygorii.strashko@ti.com> - 2016-12-06 23:40 +0100
    Re: [PATCH 4/6] net: ethernet: ti: cpts: add ptp pps support Jan Lübbe <jlu@pengutronix.de> - 2016-11-30 12:10 +0100
    Re: [PATCH 4/6] net: ethernet: ti: cpts: add ptp pps support Richard Cochran <richardcochran@gmail.com> - 2016-11-30 19:50 +0100
      Re: [PATCH 4/6] net: ethernet: ti: cpts: add ptp pps support Grygorii Strashko <grygorii.strashko@ti.com> - 2016-11-30 21:50 +0100
        Re: [PATCH 4/6] net: ethernet: ti: cpts: add ptp pps support Richard Cochran <richardcochran@gmail.com> - 2016-11-30 23:20 +0100
          Re: [PATCH 4/6] net: ethernet: ti: cpts: add ptp pps support Richard Cochran <richardcochran@gmail.com> - 2016-12-02 11:00 +0100
            Re: [PATCH 4/6] net: ethernet: ti: cpts: add ptp pps support Grygorii Strashko <grygorii.strashko@ti.com> - 2016-12-02 19:00 +0100
              Re: [PATCH 4/6] net: ethernet: ti: cpts: add ptp pps support Richard Cochran <richardcochran@gmail.com> - 2016-12-02 20:30 +0100
  [PATCH 1/6] net: ethernet: ti: netcp: add support of cpts Grygorii Strashko <grygorii.strashko@ti.com> - 2016-11-29 00:10 +0100
    Re: [PATCH 1/6] net: ethernet: ti: netcp: add support of cpts Richard Cochran <richardcochran@gmail.com> - 2016-11-30 10:50 +0100
      Re: [PATCH 1/6] net: ethernet: ti: netcp: add support of cpts Grygorii Strashko <grygorii.strashko@ti.com> - 2016-11-30 18:40 +0100
        Re: [PATCH 1/6] net: ethernet: ti: netcp: add support of cpts Richard Cochran <richardcochran@gmail.com> - 2016-11-30 19:30 +0100
    Re: [PATCH 1/6] net: ethernet: ti: netcp: add support of cpts Rob Herring <robh@kernel.org> - 2016-12-05 15:50 +0100
      Re: [PATCH 1/6] net: ethernet: ti: netcp: add support of cpts Grygorii Strashko <grygorii.strashko@ti.com> - 2016-12-05 19:30 +0100
        Re: [PATCH 1/6] net: ethernet: ti: netcp: add support of cpts Richard Cochran <richardcochran@gmail.com> - 2016-12-05 20:40 +0100

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