The current poll interval is enough to ensure that rising and falling
edge events are not lost for a 1 PPS signal with 50% duty cycle.
But when we deliver the events to user space, it will try to infer if
they were corresponding to a rising or to a falling edge (the kernel
driver doesn't know that either). User space will try to make that
inference based on the time at which the PPS master had emitted the
pulse (i.e. if it's a .0 time, it's rising edge, if it's .5 time, it's
falling edge).
But there is no in-kernel API for retrieving the precise timestamp
corresponding to a PPS master (aka perout) pulse. So user space has to
guess even that. It will read the PTP time on the PPS master right after
we've delivered the extts event, and declare that the PPS master time
was just the closest integer second, based on 2 thresholds (lower than
.25, or higher than .75, and ignore anything else).
Except that, if we poll for extts events (and our hardware doesn't
really help us, by not providing an interrupt), then there is a risk
that the poll period (and therefore the time at which the event is
delivered) might confuse user space.
Because we are always scheduling the next extts poll at
SJA1105_EXTTS_INTERVAL "from now" (that's the only thing that the
schedule_delayed_work() API gives us), it means that the start time of
the next delayed workqueue will always be shifted to the right a little
bit (shifted with the SPI access duration of this workqueue run).
In turn, because user space sees extts events that are non-periodic
compared to the PPS master's time, this means that it might start making
wrong guesses about rising/falling edge.
To understand the effect, here is the output of ts2phc currently. Notice
the 'src' timestamps of the 'SKIP extts' events, and how they have a
large wander. They keep increasing until the upper limit for the ignore
threshold (.75 seconds), after which the application starts ignoring the
_other_ edge.
ts2phc[26.624]: /dev/ptp3 SKIP extts index 0 at 21.449898912 src 21.657784518
ts2phc[27.133]: adding tstamp 21.949894240 to clock /dev/ptp3
ts2phc[27.133]: adding tstamp 22.000000000 to clock /dev/ptp1
ts2phc[27.133]: /dev/ptp3 offset 640 s2 freq +5112
ts2phc[27.636]: /dev/ptp3 SKIP extts index 0 at 22.449889360 src 22.669398022
ts2phc[28.140]: adding tstamp 22.949884376 to clock /dev/ptp3
ts2phc[28.140]: adding tstamp 23.000000000 to clock /dev/ptp1
ts2phc[28.140]: /dev/ptp3 offset 96 s2 freq +4760
ts2phc[28.644]: /dev/ptp3 SKIP extts index 0 at 23.449879504 src 23.677420422
ts2phc[29.153]: adding tstamp 23.949874704 to clock /dev/ptp3
ts2phc[29.153]: adding tstamp 24.000000000 to clock /dev/ptp1
ts2phc[29.153]: /dev/ptp3 offset -264 s2 freq +4429
ts2phc[29.656]: /dev/ptp3 SKIP extts index 0 at 24.449870008 src 24.689407238
ts2phc[30.160]: adding tstamp 24.949865376 to clock /dev/ptp3
ts2phc[30.160]: adding tstamp 25.000000000 to clock /dev/ptp1
ts2phc[30.160]: /dev/ptp3 offset -280 s2 freq +4334
ts2phc[30.664]: /dev/ptp3 SKIP extts index 0 at 25.449860760 src 25.697449926
ts2phc[31.168]: adding tstamp 25.949856176 to clock /dev/ptp3
ts2phc[31.168]: adding tstamp 26.000000000 to clock /dev/ptp1
ts2phc[31.168]: /dev/ptp3 offset -176 s2 freq +4354
ts2phc[31.672]: /dev/ptp3 SKIP extts index 0 at 26.449851584 src 26.705433606
ts2phc[32.180]: adding tstamp 26.949846992 to clock /dev/ptp3
ts2phc[32.180]: adding tstamp 27.000000000 to clock /dev/ptp1
ts2phc[32.180]: /dev/ptp3 offset -80 s2 freq +4397
ts2phc[32.684]: /dev/ptp3 SKIP extts index 0 at 27.449842384 src 27.717415110
ts2phc[33.192]: adding tstamp 27.949837768 to clock /dev/ptp3
ts2phc[33.192]: adding tstamp 28.000000000 to clock /dev/ptp1
ts2phc[33.192]: /dev/ptp3 offset 0 s2 freq +4453
ts2phc[33.696]: /dev/ptp3 SKIP extts index 0 at 28.449833128 src 28.729412902
ts2phc[34.200]: adding tstamp 28.949828472 to clock /dev/ptp3
ts2phc[34.200]: adding tstamp 29.000000000 to clock /dev/ptp1
ts2phc[34.200]: /dev/ptp3 offset 8 s2 freq +4461
ts2phc[34.704]: /dev/ptp3 SKIP extts index 0 at 29.449823816 src 29.737416038
ts2phc[35.208]: adding tstamp 29.949819152 to clock /dev/ptp3
ts2phc[35.208]: adding tstamp 30.000000000 to clock /dev/ptp1
ts2phc[35.208]: /dev/ptp3 offset -8 s2 freq +4447
ts2phc[35.712]: /dev/ptp3 SKIP extts index 0 at 30.449814496 src 30.745554982
ts2phc[36.216]: adding tstamp 30.949809840 to clock /dev/ptp3
ts2phc[36.216]: adding tstamp 31.000000000 to clock /dev/ptp1
ts2phc[36.216]: /dev/ptp3 offset -8 s2 freq +4445
ts2phc[36.468]: /dev/ptp3 SKIP extts index 0 at 31.449805184 src 31.501109446
ts2phc[36.972]: adding tstamp 31.949800536 to clock /dev/ptp3
ts2phc[36.972]: adding tstamp 32.000000000 to clock /dev/ptp1
ts2phc[36.972]: /dev/ptp3 offset -8 s2 freq +4442
ts2phc[37.480]: /dev/ptp3 SKIP extts index 0 at 32.449795896 src 32.513320070
ts2phc[37.984]: adding tstamp 32.949791248 to clock /dev/ptp3
ts2phc[37.984]: adding tstamp 33.000000000 to clock /dev/ptp1
ts2phc[37.984]: /dev/ptp3 offset 0 s2 freq +4448
Fix that by taking the following measures:
- Schedule the poll from a timer. Because we are really scheduling the
timer periodically, the extts events delivered to user space are
periodic too, and don't suffer from the "shift-to-the-right" effect.
- Increase the poll period to 6 times a second. This imposes a smaller
upper bound to the shift that can occur to the delivery time of extts
events, and makes user space (ts2phc) to always interpret correctly
which events should be skipped and which shouldn't.
- Move the SPI readout itself to the main PTP kernel thread, instead of
the generic workqueue. This is because the timer runs in atomic
context, but is also better than before, because if needed, we can
chrt & taskset this kernel thread, to ensure it gets enough priority
under load.
After this patch, one can notice that the wander is greatly reduced, and
that the latencies of one extts poll are not propagated to the next. The
'src' timestamp that is skipped is never larger than .65 seconds (which
means .15 seconds larger than the time at which the real event occurred
at, and .10 seconds smaller than the .75 upper threshold for ignoring
the falling edge):
ts2phc[40.076]: adding tstamp 34.949261296 to clock /dev/ptp3
ts2phc[40.076]: adding tstamp 35.000000000 to clock /dev/ptp1
ts2phc[40.076]: /dev/ptp3 offset 48 s2 freq +4631
ts2phc[40.568]: /dev/ptp3 SKIP extts index 0 at 35.449256496 src 35.595791078
ts2phc[41.064]: adding tstamp 35.949251744 to clock /dev/ptp3
ts2phc[41.064]: adding tstamp 36.000000000 to clock /dev/ptp1
ts2phc[41.064]: /dev/ptp3 offset -224 s2 freq +4374
ts2phc[41.552]: /dev/ptp3 SKIP extts index 0 at 36.449247088 src 36.579825574
ts2phc[42.044]: adding tstamp 36.949242456 to clock /dev/ptp3
ts2phc[42.044]: adding tstamp 37.000000000 to clock /dev/ptp1
ts2phc[42.044]: /dev/ptp3 offset -240 s2 freq +4290
ts2phc[42.536]: /dev/ptp3 SKIP extts index 0 at 37.449237848 src 37.563828774
ts2phc[43.028]: adding tstamp 37.949233264 to clock /dev/ptp3
ts2phc[43.028]: adding tstamp 38.000000000 to clock /dev/ptp1
ts2phc[43.028]: /dev/ptp3 offset -144 s2 freq +4314
ts2phc[43.520]: /dev/ptp3 SKIP extts index 0 at 38.449228656 src 38.547823238
ts2phc[44.012]: adding tstamp 38.949224048 to clock /dev/ptp3
ts2phc[44.012]: adding tstamp 39.000000000 to clock /dev/ptp1
ts2phc[44.012]: /dev/ptp3 offset -80 s2 freq +4335
ts2phc[44.508]: /dev/ptp3 SKIP extts index 0 at 39.449219432 src 39.535846118
ts2phc[44.996]: adding tstamp 39.949214816 to clock /dev/ptp3
ts2phc[44.996]: adding tstamp 40.000000000 to clock /dev/ptp1
ts2phc[44.996]: /dev/ptp3 offset -32 s2 freq +4359
ts2phc[45.488]: /dev/ptp3 SKIP extts index 0 at 40.449210192 src 40.515824678
ts2phc[45.980]: adding tstamp 40.949205568 to clock /dev/ptp3
ts2phc[45.980]: adding tstamp 41.000000000 to clock /dev/ptp1
ts2phc[45.980]: /dev/ptp3 offset 8 s2 freq +4390
ts2phc[46.636]: /dev/ptp3 SKIP extts index 0 at 41.449200928 src 41.664176902
ts2phc[47.132]: adding tstamp 41.949196288 to clock /dev/ptp3
ts2phc[47.132]: adding tstamp 42.000000000 to clock /dev/ptp1
ts2phc[47.132]: /dev/ptp3 offset 0 s2 freq +4384
ts2phc[47.620]: /dev/ptp3 SKIP extts index 0 at 42.449191656 src 42.648117190
ts2phc[48.112]: adding tstamp 42.949187016 to clock /dev/ptp3
ts2phc[48.112]: adding tstamp 43.000000000 to clock /dev/ptp1
ts2phc[48.112]: /dev/ptp3 offset 0 s2 freq +4384
ts2phc[48.604]: /dev/ptp3 SKIP extts index 0 at 43.449182384 src 43.632112582
ts2phc[49.100]: adding tstamp 43.949177736 to clock /dev/ptp3
ts2phc[49.100]: adding tstamp 44.000000000 to clock /dev/ptp1
ts2phc[49.100]: /dev/ptp3 offset -8 s2 freq +4376
ts2phc[49.588]: /dev/ptp3 SKIP extts index 0 at 44.449173096 src 44.616136774
ts2phc[50.080]: adding tstamp 44.949168464 to clock /dev/ptp3
ts2phc[50.080]: adding tstamp 45.000000000 to clock /dev/ptp1
ts2phc[50.080]: /dev/ptp3 offset 8 s2 freq +4390
ts2phc[50.572]: /dev/ptp3 SKIP extts index 0 at 45.449163816 src 45.600134662
ts2phc[51.064]: adding tstamp 45.949159160 to clock /dev/ptp3
ts2phc[51.064]: adding tstamp 46.000000000 to clock /dev/ptp1
ts2phc[51.064]: /dev/ptp3 offset -8 s2 freq +4376
ts2phc[51.556]: /dev/ptp3 SKIP extts index 0 at 46.449154528 src 46.584588550
ts2phc[52.048]: adding tstamp 46.949149896 to clock /dev/ptp3
ts2phc[52.048]: adding tstamp 47.000000000 to clock /dev/ptp1
ts2phc[52.048]: /dev/ptp3 offset 0 s2 freq +4382
ts2phc[52.540]: /dev/ptp3 SKIP extts index 0 at 47.449145256 src 47.568132198
ts2phc[53.032]: adding tstamp 47.949140616 to clock /dev/ptp3
ts2phc[53.032]: adding tstamp 48.000000000 to clock /dev/ptp1
ts2phc[53.032]: /dev/ptp3 offset 0 s2 freq +4382
ts2phc[53.524]: /dev/ptp3 SKIP extts index 0 at 48.449135968 src 48.552121446
ts2phc[54.016]: adding tstamp 48.949131320 to clock /dev/ptp3
ts2phc[54.016]: adding tstamp 49.000000000 to clock /dev/ptp1
ts2phc[54.016]: /dev/ptp3 offset 0 s2 freq +4382
ts2phc[54.512]: /dev/ptp3 SKIP extts index 0 at 49.449126680 src 49.540147014
ts2phc[55.000]: adding tstamp 49.949122040 to clock /dev/ptp3
ts2phc[55.000]: adding tstamp 50.000000000 to clock /dev/ptp1
ts2phc[55.000]: /dev/ptp3 offset 0 s2 freq +4382
ts2phc[55.492]: /dev/ptp3 SKIP extts index 0 at 50.449117400 src 50.520119078
ts2phc[55.988]: adding tstamp 50.949112768 to clock /dev/ptp3
ts2phc[55.988]: adding tstamp 51.000000000 to clock /dev/ptp1
ts2phc[55.988]: /dev/ptp3 offset 8 s2 freq +4390
ts2phc[56.476]: /dev/ptp3 SKIP extts index 0 at 51.449108120 src 51.504175910
ts2phc[57.132]: adding tstamp 51.949103480 to clock /dev/ptp3
ts2phc[57.132]: adding tstamp 52.000000000 to clock /dev/ptp1
ts2phc[57.132]: /dev/ptp3 offset 0 s2 freq +4384
ts2phc[57.624]: /dev/ptp3 SKIP extts index 0 at 52.449098840 src 52.651833574
ts2phc[58.116]: adding tstamp 52.949094200 to clock /dev/ptp3
ts2phc[58.116]: adding tstamp 53.000000000 to clock /dev/ptp1
ts2phc[58.116]: /dev/ptp3 offset 8 s2 freq +4392
ts2phc[58.612]: /dev/ptp3 SKIP extts index 0 at 53.449089560 src 53.639826918
ts2phc[59.100]: adding tstamp 53.949084920 to clock /dev/ptp3
ts2phc[59.100]: adding tstamp 54.000000000 to clock /dev/ptp1
ts2phc[59.100]: /dev/ptp3 offset 8 s2 freq +4394
ts2phc[59.592]: /dev/ptp3 SKIP extts index 0 at 54.449080272 src 54.619842278
ts2phc[60.084]: adding tstamp 54.949075624 to clock /dev/ptp3
ts2phc[60.084]: adding tstamp 55.000000000 to clock /dev/ptp1
ts2phc[60.084]: /dev/ptp3 offset 8 s2 freq +4397
ts2phc[60.576]: /dev/ptp3 SKIP extts index 0 at 55.449070968 src 55.603885542
ts2phc[61.068]: adding tstamp 55.949066312 to clock /dev/ptp3
ts2phc[61.068]: adding tstamp 56.000000000 to clock /dev/ptp1
ts2phc[61.068]: /dev/ptp3 offset 0 s2 freq +4391
ts2phc[61.560]: /dev/ptp3 SKIP extts index 0 at 56.449061680 src 56.587885798
ts2phc[62.052]: adding tstamp 56.949057032 to clock /dev/ptp3
ts2phc[62.052]: adding tstamp 57.000000000 to clock /dev/ptp1
ts2phc[62.052]: /dev/ptp3 offset -8 s2 freq +4383
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Restrict the TTEthernet hardware support on this switch to operate as
closely as possible to IEEE 802.1Qci as possible. This means that it can
perform PTP-time-based ingress admission control on streams identified
by {DMAC, VID, PCP}, which is useful when trying to ensure the
determinism of traffic scheduled via IEEE 802.1Qbv.
The oddity comes from the fact that in hardware (and in TTEthernet at
large), virtual links always need a full-blown action, including not
only the type of policing, but also the list of destination ports. So in
practice, a single tc-gate action will result in all packets getting
dropped. Additional actions (either "trap" or "redirect") need to be
specified in the same filter rule such that the conforming packets are
actually forwarded somewhere.
Apart from the VL Lookup, Policing and Forwarding tables which need to
be programmed for each flow (virtual link), the Schedule engine also
needs to be told to open/close the admission gates for each individual
virtual link. A fairly accurate (and detailed) description of how that
works is already present in sja1105_tas.c, since it is already used to
trigger the egress gates for the tc-taprio offload (IEEE 802.1Qbv). Key
point here, we remember that the schedule engine supports 8
"subschedules" (execution threads that iterate through the global
schedule in parallel, and that no 2 hardware threads must execute a
schedule entry at the same time). For tc-taprio, each egress port used
one of these 8 subschedules, leaving a total of 4 subschedules unused.
In principle we could have allocated 1 subschedule for the tc-gate
offload of each ingress port, but actually the schedules of all virtual
links installed on each ingress port would have needed to be merged
together, before they could have been programmed to hardware. So
simplify our life and just merge the entire tc-gate configuration, for
all virtual links on all ingress ports, into a single subschedule. Be
sure to check that against the usual hardware scheduling conflicts, and
program it to hardware alongside any tc-taprio subschedule that may be
present.
The following scenarios were tested:
1. Quantitative testing:
tc qdisc add dev swp2 clsact
tc filter add dev swp2 ingress flower skip_sw \
dst_mac 42:be:24:9b:76:20 \
action gate index 1 base-time 0 \
sched-entry OPEN 1200 -1 -1 \
sched-entry CLOSE 1200 -1 -1 \
action trap
ping 192.168.1.2 -f
PING 192.168.1.2 (192.168.1.2) 56(84) bytes of data.
.............................
--- 192.168.1.2 ping statistics ---
948 packets transmitted, 467 received, 50.7384% packet loss, time 9671ms
2. Qualitative testing (with a phase-aligned schedule - the clocks are
synchronized by ptp4l, not shown here):
Receiver (sja1105):
tc qdisc add dev swp2 clsact
now=$(phc_ctl /dev/ptp1 get | awk '/clock time is/ {print $5}') && \
sec=$(echo $now | awk -F. '{print $1}') && \
base_time="$(((sec + 2) * 1000000000))" && \
echo "base time ${base_time}"
tc filter add dev swp2 ingress flower skip_sw \
dst_mac 42:be:24:9b:76:20 \
action gate base-time ${base_time} \
sched-entry OPEN 60000 -1 -1 \
sched-entry CLOSE 40000 -1 -1 \
action trap
Sender (enetc):
now=$(phc_ctl /dev/ptp0 get | awk '/clock time is/ {print $5}') && \
sec=$(echo $now | awk -F. '{print $1}') && \
base_time="$(((sec + 2) * 1000000000))" && \
echo "base time ${base_time}"
tc qdisc add dev eno0 parent root taprio \
num_tc 8 \
map 0 1 2 3 4 5 6 7 \
queues 1@0 1@1 1@2 1@3 1@4 1@5 1@6 1@7 \
base-time ${base_time} \
sched-entry S 01 50000 \
sched-entry S 00 50000 \
flags 2
ping -A 192.168.1.1
PING 192.168.1.1 (192.168.1.1): 56 data bytes
...
^C
--- 192.168.1.1 ping statistics ---
1425 packets transmitted, 1424 packets received, 0% packet loss
round-trip min/avg/max = 0.322/0.361/0.990 ms
And just for comparison, with the tc-taprio schedule deleted:
ping -A 192.168.1.1
PING 192.168.1.1 (192.168.1.1): 56 data bytes
...
^C
--- 192.168.1.1 ping statistics ---
33 packets transmitted, 19 packets received, 42% packet loss
round-trip min/avg/max = 0.336/0.464/0.597 ms
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The SJA1105 switch family has a PTP_CLK pin which emits a signal with
fixed 50% duty cycle, but variable frequency and programmable start time.
On the second generation (P/Q/R/S) switches, this pin supports even more
functionality. The use case described by the hardware documents talks
about synchronization via oneshot pulses: given 2 sja1105 switches,
arbitrarily designated as a master and a slave, the master emits a
single pulse on PTP_CLK, while the slave is configured to timestamp this
pulse received on its PTP_CLK pin (which must obviously be configured as
input). The difference between the timestamps then exactly becomes the
slave offset to the master.
The only trouble with the above is that the hardware is very much tied
into this use case only, and not very generic beyond that:
- When emitting a oneshot pulse, instead of being told when to emit it,
the switch just does it "now" and tells you later what time it was,
via the PTPSYNCTS register. [ Incidentally, this is the same register
that the slave uses to collect the ext_ts timestamp from, too. ]
- On the sync slave, there is no interrupt mechanism on reception of a
new extts, and no FIFO to buffer them, because in the foreseen use
case, software is in control of both the master and the slave pins,
so it "knows" when there's something to collect.
These 2 problems mean that:
- We don't support (at least yet) the quirky oneshot mode exposed by
the hardware, just normal periodic output.
- We abuse the hardware a little bit when we expose generic extts.
Because there's no interrupt mechanism, we need to poll at double the
frequency we expect to receive a pulse. Currently that means a
non-configurable "twice a second".
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Because the PTP_CLK pin starts toggling only at a time higher than the
current PTP clock, this helper from the time-aware shaper code comes in
handy here as well. We'll use it to transform generic user input for the
perout request into valid input for the sja1105 hardware.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
And move the queue of skb's waiting for RX timestamps into the ptp_data
structure, since it isn't needed if PTP is not compiled.
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Tested using the following bash script and the tc from iproute2-next:
#!/bin/bash
set -e -u -o pipefail
NSEC_PER_SEC="1000000000"
gatemask() {
local tc_list="$1"
local mask=0
for tc in ${tc_list}; do
mask=$((${mask} | (1 << ${tc})))
done
printf "%02x" ${mask}
}
if ! systemctl is-active --quiet ptp4l; then
echo "Please start the ptp4l service"
exit
fi
now=$(phc_ctl /dev/ptp1 get | gawk '/clock time is/ { print $5; }')
# Phase-align the base time to the start of the next second.
sec=$(echo "${now}" | gawk -F. '{ print $1; }')
base_time="$(((${sec} + 1) * ${NSEC_PER_SEC}))"
tc qdisc add dev swp5 parent root handle 100 taprio \
num_tc 8 \
map 0 1 2 3 5 6 7 \
queues 1@0 1@1 1@2 1@3 1@4 1@5 1@6 1@7 \
base-time ${base_time} \
sched-entry S $(gatemask 7) 100000 \
sched-entry S $(gatemask "0 1 2 3 4 5 6") 400000 \
clockid CLOCK_TAI flags 2
The "state machine" is a workqueue invoked after each manipulation
command on the PTP clock (reset, adjust time, set time, adjust
frequency) which checks over the state of the time-aware scheduler.
So it is not monitored periodically, only in reaction to a PTP command
typically triggered from a userspace daemon (linuxptp). Otherwise there
is no reason for things to go wrong.
Now that the timecounter/cyclecounter has been replaced with hardware
operations on the PTP clock, the TAS Kconfig now depends upon PTP and
the standalone clocksource operating mode has been removed.
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The PTPSTRTSCH and PTPSTOPSCH bits are actually readable and indicate
whether the time-aware scheduler is running or not. We will be using
that for monitoring the scheduler in the next patch, so refactor the PTP
command API in order to allow that.
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The PTP time of the switch is not preserved when uploading a new static
configuration. Work around this hardware oddity by reading its PTP time
before a static config upload, and restoring it afterwards.
Static config changes are expected to occur at runtime even in scenarios
directly related to PTP, i.e. the Time-Aware Scheduler of the switch is
programmed in this way.
Perhaps the larger implication of this patch is that the PTP .gettimex64
and .settime functions need to be exposed to sja1105_main.c, where the
PTP lock needs to be held during this entire process. So their core
implementation needs to move to some common functions which get exposed
in sja1105_ptp.h.
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Adjusting the hardware clock (PTPCLKVAL, PTPCLKADD, PTPCLKRATE) is a
requirement for the auxiliary PTP functionality of the switch
(TTEthernet, PPS input, PPS output).
Therefore we need to switch to using these registers to keep a
synchronized time in hardware, instead of the timecounter/cyclecounter
implementation, which is reliant on the free-running PTPTSCLK.
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This patch corrects the SPDX License Identifier style
in header files related to Distributed Switch Architecture
drivers for NXP SJA1105 series Ethernet switch support.
It uses an expilict block comment for the SPDX License
Identifier.
Changes made by using a script provided by Joe Perches here:
https://lkml.org/lkml/2019/2/7/46.
Suggested-by: Joe Perches <joe@perches.com>
Signed-off-by: Nishad Kamdar <nishadkamdar@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
The PTP command register contains enable bits for:
- Putting the 64-bit PTPCLKVAL register in add/subtract or write mode
- Taking timestamps off of the corrected vs free-running clock
- Starting/stopping the TTEthernet scheduling
- Starting/stopping PPS output
- Resetting the switch
When a command needs to be issued (e.g. "change the PTPCLKVAL from write
mode to add/subtract mode"), one cannot simply write to the command
register setting the PTPCLKADD bit to 1, because that would zeroize the
other settings. One also cannot do a read-modify-write (that would be
too easy for this hardware) because not all bits of the command register
are readable over SPI.
So this leaves us with the only option of keeping the value of the PTP
command register in the driver, and operating on that.
Actually there are 2 types of PTP operations now:
- Operations that modify the cached PTP command. These operate on
ptp_data->cmd as a pointer.
- Operations that apply all previously cached PTP settings, but don't
otherwise cache what they did themselves. The sja1105_ptp_reset
function is such an example. It copies the ptp_data->cmd on stack
before modifying and writing it to SPI.
This practically means that struct sja1105_ptp_cmd is no longer an
implementation detail, since it needs to be stored in full into struct
sja1105_ptp_data, and hence in struct sja1105_private. So the (*ptp_cmd)
function prototype can change and take struct sja1105_ptp_cmd as second
argument now.
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This is a non-functional change with 2 goals (both for the case when
CONFIG_NET_DSA_SJA1105_PTP is not enabled):
- Reduce the size of the sja1105_private structure.
- Make the PTP code more self-contained.
Leaving priv->ptp_data.lock to be initialized in sja1105_main.c is not a
leftover: it will be used in a future patch "net: dsa: sja1105: Restore
PTP time after switch reset".
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The new rule (as already started for sja1105_tas.h) is for functions of
optional driver components (ones which may be disabled via Kconfig - PTP
and TAS) to take struct dsa_switch *ds instead of struct sja1105_private
*priv as first argument.
This is so that forward-declarations of struct sja1105_private can be
avoided.
So make sja1105_ptp.h the second user of this rule.
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
On TX, timestamping is performed synchronously from the
port_deferred_xmit worker thread.
In management routes, the switch is requested to take egress timestamps
(again partial), which are reconstructed and appended to a clone of the
skb that was just sent. The cloning is done by DSA and we retrieve the
pointer from the structure that DSA keeps in skb->cb.
Then these clones are enqueued to the socket's error queue for
application-level processing.
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The design of this PHC driver is influenced by the switch's behavior
w.r.t. timestamping. It exposes two PTP counters, one free-running
(PTPTSCLK) and the other offset- and frequency-corrected in hardware
through PTPCLKVAL, PTPCLKADD and PTPCLKRATE. The MACs can sample either
of these for frame timestamps.
However, the user manual warns that taking timestamps based on the
corrected clock is less than useful, as the switch can deliver corrupted
timestamps in a variety of circumstances.
Therefore, this PHC uses the free-running PTPTSCLK together with a
timecounter/cyclecounter structure that translates it into a software
time domain. Thus, the settime/adjtime and adjfine callbacks are
hardware no-ops.
The timestamps (introduced in a further patch) will also be translated
to the correct time domain before being handed over to the userspace PTP
stack.
The introduction of a second set of PHC operations that operate on the
hardware PTPCLKVAL/PTPCLKADD/PTPCLKRATE in the future is somewhat
unavoidable, as the TTEthernet core uses the corrected PTP time domain.
However, the free-running counter + timecounter structure combination
will suffice for now, as the resulting timestamps yield a sub-50 ns
synchronization offset in steady state using linuxptp.
For this patch, in absence of frame timestamping, the operations of the
switch PHC were tested by syncing it to the system time as a local slave
clock with:
phc2sys -s CLOCK_REALTIME -c swp2 -O 0 -m -S 0.01
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
