1.
But it(to get 1pps signal out of sdp via FREQOUT) seems to be undoable, due to
the following reasons:
Let's say TIMINCA.Incvalue = 0xCCCCCC(default value from the driver for 82599)
and TIMINCA.Incperiod=2(T=6,4ns), than
to get 1Hz(T=10^9 ns) we need 10^9/12,8 cycles to generate 1Hz and value to be
written to the FREQOUT register must be
(10^9/12,8)*0xCCCCCC and it's turned out to be larger then maximum value for 32
bit register.
2.
For generating frequency out of sdp via FREQOUT, is FREQOUT register must be
rewritten every time it reaches zero?
> <http://sourceforge.net>Does exist any way to generate PPS signal on sdp for
> 82599?
> I mean, some software, like ptp4l, adjusts SYSTIM of 82599, using TIMINCA and
> it generate PPS signal on one of sdp(out).
> It seems, ixgbe has such solution for X540 (ixgbe_ptp.c
> ixgbe_ptp_setup_sdp_X540())
>
> Regards, Maksim
>
> > In NIC 82599, there is option to generate frequency via sdp(configured
> > as out) - in data sheet it appears in red in 2.png . That frequency is
> > determined by FREQOUT0/1 register, as it appears in blue in
> > 1.png(attached here). I could not understand how that RLV is set. For
> > example, if I need 1Hz to be out via that sdp.
> > Thanks for advance, and sorry to bother.
> >
> > Regards, Maksim
You can generate frequency outputs on SDP pins, using this feature,
however it depends on how you set the TIMINCA register, that determines
how fast SYSTIM advanced.
There is a limitation on this as well, that any period output of the SDP
has to be an exact multiple of twice the internal clock period that
drives the TimeSync features. For the 82599, that is documented in the
datasheet as 6.4 nanoseconds, which means the minimum period for the SDP
output will be 12.8 nanoseconds. In addition, NO period which is not an
exact multiple of 12.8 nanoseconds will be able to be generated. You
would have to keep that in mind when determining exactly what output
frequency you wanted.
Generally, the clock works by adding TIMINCA register value to SYSTIME
every internal clock tick. It also subtracts the TIMINCA value from the
FREQOUT register, storing it in an internal countdown. Once the
countdown register reaches 0, it will perform a level change on the SDP.
You would have to determine the FREQOUT value as a multiple of TIMINCA
for best behavior of a periodic output on the SDP.
Regards,
Jake
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