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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>
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These fields configure the destination and source MAC address that the
switch will put in the Ethernet frames sent towards the CPU port that
contain RX timestamps for PTP.
These fields do not enable the feature itself, that is configured via
SEND_META0 and SEND_META1 in the General Params table.
The implication of this patch is that the AVB Params table will always
be present in the static config. Which doesn't really hurt.
This is needed because in a future patch, we will add another field from
this table, CAS_MASTER, for configuring the PTP_CLK pin function. That
can be configured irrespective of whether RX timestamping is enabled or
not, so always having this table present is going to simplify things a
bit.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Simple overlapping changes in bpf land wrt. bpf_helper_defs.h
handling.
Signed-off-by: David S. Miller <davem@davemloft.net>
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When disabling PTP timestamping, don't reset the switch with the new
static config until all existing PTP frames have been timestamped on the
RX path or dropped. There's nothing we can do with these afterwards.
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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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>
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When activating tc-taprio offload on the switch ports, the TAS state
machine will try to check whether it is running or not, but will find
both the STARTED and STOPPED bits as false in the
sja1105_tas_check_running function. So the function will return -EINVAL
(an abnormal situation) and the kernel will keep printing this from the
TAS FSM workqueue:
[ 37.691971] sja1105 spi0.1: An operation returned -22
The reason is that the underlying function that gets called,
sja1105_ptp_commit, does not actually do a SPI_READ, but a SPI_WRITE. So
the command buffer remains initialized with zeroes instead of retrieving
the hardware state. Fix that.
Fixes: 41603d78b362 ("net: dsa: sja1105: Make the PTP command read-write")
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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The PTP egress timestamp N must be captured from register PTPEGR_TS[n],
where n = 2 * PORT + TSREG. There are 10 PTPEGR_TS registers, 2 per
port. We are only using TSREG=0.
As opposed to the management slots, which are 4 in number
(SJA1105_NUM_PORTS, minus the CPU port). Any management frame (which
includes PTP frames) can be sent to any non-CPU port through any
management slot. When the CPU port is not the last port (#4), there will
be a mismatch between the slot and the port number.
Luckily, the only mainline occurrence with this switch
(arch/arm/boot/dts/ls1021a-tsn.dts) does have the CPU port as #4, so the
issue did not manifest itself thus far.
Fixes: 47ed985e97f5 ("net: dsa: sja1105: Add logic for TX timestamping")
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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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>
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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>
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Sometimes it can be quite opaque even for me why the driver decided to
reset the switch. So instead of adding dump_stack() calls each time for
debugging, just add a reset reason to sja1105_static_config_reload
calls which gets printed to the console.
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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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>
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Through the PTP_SYS_OFFSET_EXTENDED ioctl, it is possible for userspace
applications (i.e. phc2sys) to compensate for the delays incurred while
reading the PHC's time.
The task itself of taking the software timestamp is delegated to the SPI
subsystem, through the newly introduced API in struct spi_transfer. The
goal is to cross-timestamp I/O operations on the switch's PTP clock with
values in the local system clock (CLOCK_REALTIME). For that we need to
understand a bit of the hardware internals.
The 'read PTP time' message is a 12 byte structure, first 4 bytes of
which represent the SPI header, and the last 8 bytes represent the
64-bit PTP time. The switch itself starts processing the command
immediately after receiving the last bit of the address, i.e. at the
middle of byte 3 (last byte of header). The PTP time is shadowed to a
buffer register in the switch, and retrieved atomically during the
subsequent SPI frames.
A similar thing goes on for the 'write PTP time' message, although in
that case the switch waits until the 64-bit PTP time becomes fully
available before taking any action. So the byte that needs to be
software-timestamped is byte 11 (last) of the transfer.
The patch creates a common (and local) sja1105_xfer implementation for
the SPI I/O, and offers 3 front-ends:
- sja1105_xfer_u32 and sja1105_xfer_u64: these are capable of optionally
requesting a PTP timestamp
- sja1105_xfer_buf: this is for large transfers (e.g. the static config
buffer) and other misc data, and there is no point in giving
timestamping capabilities to this.
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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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>
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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>
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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>
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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>
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We need priv->ptp_caps to hold a structure and not just a pointer,
because we use container_of in the various PTP callbacks.
Therefore, the sja1105_ptp_caps structure declared in the global memory
of the driver serves no further purpose after copying it into
priv->ptp_caps.
So just populate priv->ptp_caps with the needed operations and remove
sja1105_ptp_caps.
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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The most commonly called function in the driver is long due for a
rename. The "packed" word is redundant (it doesn't make sense to
transfer an unpacked structure, since that is in CPU endianness yadda
yadda), and the "spi" word is also redundant since argument 2 of the
function is SPI_READ or SPI_WRITE.
As for the sja1105_spi_send_long_packed_buf function, it is only being
used from sja1105_spi.c, so remove its global prototype.
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Having a function that takes a variable number of unpacked bytes which
it generically calls an "int" is confusing and makes auditing patches
next to impossible.
We only use spi_send_int with the int sizes of 32 and 64 bits. So just
make the spi_send_int function less generic and replace it with the
appropriate two explicit functions, which can now type-check the int
pointer type.
Note that there is still a small weirdness in the u32 function, which
has to convert it to a u64 temporary. This is because of how the packing
API works at the moment, but the weirdness is at least hidden from
callers of sja1105_xfer_u32 now.
Suggested-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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The IS_ERR_OR_NULL(priv->clock) check inside
sja1105_ptp_clock_unregister() is preventing cancel_delayed_work_sync
from actually being run.
Additionally, sja1105_ptp_clock_unregister() does not actually get run,
when placed in sja1105_remove(). The DSA switch gets torn down, but the
sja1105 module does not get unregistered. So sja1105_ptp_clock_unregister
needs to be moved to sja1105_teardown, to be symmetrical with
sja1105_ptp_clock_register which is called from the DSA sja1105_setup.
It is strange to fix a "fixes" patch, but the probe failure can only be
seen when the attached PHY does not respond to MDIO (issue which I can't
pinpoint the reason to) and it goes away after I power-cycle the board.
This time the patch was validated on a failing board, and the kernel
panic from the fixed commit's message can no longer be seen.
Fixes: 29dd908d355f ("net: dsa: sja1105: Cancel PTP delayed work on unregister")
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Currently when the driver unloads and PTP is enabled, the delayed work
that prevents the timecounter from expiring becomes a ticking time bomb.
The kernel will schedule the work thread within 60 seconds of driver
removal, but the work handler is no longer there, leading to this
strange and inconclusive stack trace:
[ 64.473112] Unable to handle kernel paging request at virtual address 79746970
[ 64.480340] pgd = 008c4af9
[ 64.483042] [79746970] *pgd=00000000
[ 64.486620] Internal error: Oops: 80000005 [#1] SMP ARM
[ 64.491820] Modules linked in:
[ 64.494871] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.2.0-rc5-01634-ge3a2773ba9e5 #1246
[ 64.503007] Hardware name: Freescale LS1021A
[ 64.507259] PC is at 0x79746970
[ 64.510393] LR is at call_timer_fn+0x3c/0x18c
[ 64.514729] pc : [<79746970>] lr : [<c03bd734>] psr: 60010113
[ 64.520965] sp : c1901de0 ip : 00000000 fp : c1903080
[ 64.526163] r10: c1901e38 r9 : ffffe000 r8 : c19064ac
[ 64.531363] r7 : 79746972 r6 : e98dd260 r5 : 00000100 r4 : c1a9e4a0
[ 64.537859] r3 : c1900000 r2 : ffffa400 r1 : 79746972 r0 : e98dd260
[ 64.544359] Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none
[ 64.551460] Control: 10c5387d Table: a8a2806a DAC: 00000051
[ 64.557176] Process swapper/0 (pid: 0, stack limit = 0x1ddb27f0)
[ 64.563147] Stack: (0xc1901de0 to 0xc1902000)
[ 64.567481] 1de0: eb6a4918 3d60d7c3 c1a9e554 e98dd260 eb6a34c0 c1a9e4a0 ffffa400 c19064ac
[ 64.575616] 1e00: ffffe000 c03bd95c c1901e34 c1901e34 eb6a34c0 c1901e30 c1903d00 c186f4c0
[ 64.583751] 1e20: c1906488 29e34000 c1903080 c03bdca4 00000000 eaa6f218 00000000 eb6a45c0
[ 64.591886] 1e40: eb6a45c0 20010193 00000003 c03c0a68 20010193 3f7231be c1903084 00000002
[ 64.600022] 1e60: 00000082 00000001 ffffe000 c1a9e0a4 00000100 c0302298 02b64722 0000000f
[ 64.608157] 1e80: c186b3c8 c1877540 c19064ac 0000000a c186b350 ffffa401 c1903d00 c1107348
[ 64.616292] 1ea0: 00200102 c0d87a14 ea823c00 ffffe000 00000012 00000000 00000000 ea810800
[ 64.624427] 1ec0: f0803000 c1876ba8 00000000 c034c784 c18774b8 c039fb50 c1906c90 c1978aac
[ 64.632562] 1ee0: f080200c f0802000 c1901f10 c0709ca8 c03091a0 60010013 ffffffff c1901f44
[ 64.640697] 1f00: 00000000 c1900000 c1876ba8 c0301a8c 00000000 000070a0 eb6ac1a0 c031da60
[ 64.648832] 1f20: ffffe000 c19064ac c19064f0 00000001 00000000 c1906488 c1876ba8 00000000
[ 64.656967] 1f40: ffffffff c1901f60 c030919c c03091a0 60010013 ffffffff 00000051 00000000
[ 64.665102] 1f60: ffffe000 c0376aa4 c1a9da37 ffffffff 00000037 3f7231be c1ab20c0 000000cc
[ 64.673238] 1f80: c1906488 c1906480 ffffffff 00000037 c1ab20c0 c1ab20c0 00000001 c0376e1c
[ 64.681373] 1fa0: c1ab2118 c1700ea8 ffffffff ffffffff 00000000 c1700754 c17dfa40 ebfffd80
[ 64.689509] 1fc0: 00000000 c17dfa40 3f7733be 00000000 00000000 c1700330 00000051 10c0387d
[ 64.697644] 1fe0: 00000000 8f000000 410fc075 10c5387d 00000000 00000000 00000000 00000000
[ 64.705788] [<c03bd734>] (call_timer_fn) from [<c03bd95c>] (expire_timers+0xd8/0x144)
[ 64.713579] [<c03bd95c>] (expire_timers) from [<c03bdca4>] (run_timer_softirq+0xe4/0x1dc)
[ 64.721716] [<c03bdca4>] (run_timer_softirq) from [<c0302298>] (__do_softirq+0x130/0x3c8)
[ 64.729854] [<c0302298>] (__do_softirq) from [<c034c784>] (irq_exit+0xbc/0xd8)
[ 64.737040] [<c034c784>] (irq_exit) from [<c039fb50>] (__handle_domain_irq+0x60/0xb4)
[ 64.744833] [<c039fb50>] (__handle_domain_irq) from [<c0709ca8>] (gic_handle_irq+0x58/0x9c)
[ 64.753143] [<c0709ca8>] (gic_handle_irq) from [<c0301a8c>] (__irq_svc+0x6c/0x90)
[ 64.760583] Exception stack(0xc1901f10 to 0xc1901f58)
[ 64.765605] 1f00: 00000000 000070a0 eb6ac1a0 c031da60
[ 64.773740] 1f20: ffffe000 c19064ac c19064f0 00000001 00000000 c1906488 c1876ba8 00000000
[ 64.781873] 1f40: ffffffff c1901f60 c030919c c03091a0 60010013 ffffffff
[ 64.788456] [<c0301a8c>] (__irq_svc) from [<c03091a0>] (arch_cpu_idle+0x38/0x3c)
[ 64.795816] [<c03091a0>] (arch_cpu_idle) from [<c0376aa4>] (do_idle+0x1bc/0x298)
[ 64.803175] [<c0376aa4>] (do_idle) from [<c0376e1c>] (cpu_startup_entry+0x18/0x1c)
[ 64.810707] [<c0376e1c>] (cpu_startup_entry) from [<c1700ea8>] (start_kernel+0x480/0x4ac)
[ 64.818839] Code: bad PC value
[ 64.821890] ---[ end trace e226ed97b1c584cd ]---
[ 64.826482] Kernel panic - not syncing: Fatal exception in interrupt
[ 64.832807] CPU1: stopping
[ 64.835501] CPU: 1 PID: 0 Comm: swapper/1 Tainted: G D 5.2.0-rc5-01634-ge3a2773ba9e5 #1246
[ 64.845013] Hardware name: Freescale LS1021A
[ 64.849266] [<c0312394>] (unwind_backtrace) from [<c030cc74>] (show_stack+0x10/0x14)
[ 64.856972] [<c030cc74>] (show_stack) from [<c0ff4138>] (dump_stack+0xb4/0xc8)
[ 64.864159] [<c0ff4138>] (dump_stack) from [<c0310854>] (handle_IPI+0x3bc/0x3dc)
[ 64.871519] [<c0310854>] (handle_IPI) from [<c0709ce8>] (gic_handle_irq+0x98/0x9c)
[ 64.879050] [<c0709ce8>] (gic_handle_irq) from [<c0301a8c>] (__irq_svc+0x6c/0x90)
[ 64.886489] Exception stack(0xea8cbf60 to 0xea8cbfa8)
[ 64.891514] bf60: 00000000 0000307c eb6c11a0 c031da60 ffffe000 c19064ac c19064f0 00000002
[ 64.899649] bf80: 00000000 c1906488 c1876ba8 00000000 00000000 ea8cbfb0 c030919c c03091a0
[ 64.907780] bfa0: 600d0013 ffffffff
[ 64.911250] [<c0301a8c>] (__irq_svc) from [<c03091a0>] (arch_cpu_idle+0x38/0x3c)
[ 64.918609] [<c03091a0>] (arch_cpu_idle) from [<c0376aa4>] (do_idle+0x1bc/0x298)
[ 64.925967] [<c0376aa4>] (do_idle) from [<c0376e1c>] (cpu_startup_entry+0x18/0x1c)
[ 64.933496] [<c0376e1c>] (cpu_startup_entry) from [<803025cc>] (0x803025cc)
[ 64.940422] Rebooting in 3 seconds..
In this case, what happened is that the DSA driver failed to probe at
boot time due to a PHY issue during phylink_connect_phy:
[ 2.245607] fsl-gianfar soc:ethernet@2d90000 eth2: error -19 setting up slave phy
[ 2.258051] sja1105 spi0.1: failed to create slave for port 0.0
Fixes: bb77f36ac21d ("net: dsa: sja1105: Add support for the PTP clock")
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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As Arnd Bergmann pointed out in commit 78fe8a28fb96 ("net: dsa: sja1105:
fix ptp link error"), there is no point in having PTP support as a
separate loadable kernel module.
So remove the exported symbols and make sja1105.ko contain PTP support
or not based on CONFIG_NET_DSA_SJA1105_PTP.
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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This enables the PTP support towards userspace applications such as
linuxptp.
The switches can timestamp only trapped multicast MAC frames, and
therefore only the profiles of 1588 over L2 are supported.
TX timestamping can be enabled per port, but RX timestamping is enabled
globally. As long as RX timestamping is enabled, the switch will emit
metadata follow-up frames that will be processed by the tagger. It may
be a problem that linuxptp does not restore the RX timestamping settings
when exiting.
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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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>
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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>
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