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author | Ben Hutchings <bhutchings@solarflare.com> | 2014-02-12 18:58:46 +0000 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2014-02-12 17:53:34 -0500 |
commit | 92d8f766ecce190dc2aa5d1aa9a5f5381e831641 (patch) | |
tree | 667ccab328087bc603b872f2dd4b8f1e9d4f6f4f /drivers/net/ethernet/sfc | |
parent | ce320f44d677549a29ae8d6ae79e66d1c997f87a (diff) | |
download | op-kernel-dev-92d8f766ecce190dc2aa5d1aa9a5f5381e831641.zip op-kernel-dev-92d8f766ecce190dc2aa5d1aa9a5f5381e831641.tar.gz |
sfc: Rewrite adjustment of PPS event in a clearer way
There is substantial latency in generation and handling of PPS events
from the NIC, which we have to correct for before passing a host
timestamp to the PPS subsystem. We compare clocks with the MC,
giving us two offsets to subtract from the timestamp generated by
pps_get_ts():
(a) Time from the last good sync (where we got host and NIC timestamps
for nearly the same instant) to the time we called pps_get_ts()
(b) Time from NIC top of second to the last good sync
We currently calculate (a) + (b) in a quite confusing way.
Instead, calculate (a) completely, then add (b) to it.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/ethernet/sfc')
-rw-r--r-- | drivers/net/ethernet/sfc/ptp.c | 47 |
1 files changed, 23 insertions, 24 deletions
diff --git a/drivers/net/ethernet/sfc/ptp.c b/drivers/net/ethernet/sfc/ptp.c index 7d0de50..28275e3 100644 --- a/drivers/net/ethernet/sfc/ptp.c +++ b/drivers/net/ethernet/sfc/ptp.c @@ -766,37 +766,36 @@ efx_ptp_process_times(struct efx_nic *efx, MCDI_DECLARE_STRUCT_PTR(synch_buf), return -EAGAIN; } - /* Convert the NIC time into kernel time. No correction is required- - * this time is the output of a firmware process. - */ - mc_time = ptp->nic_to_kernel_time(ptp->timeset[last_good].major, - ptp->timeset[last_good].minor, 0); - - /* Calculate delay from actual PPS to last_time */ - delta = ktime_to_timespec(mc_time); - delta.tv_nsec += - last_time->ts_real.tv_nsec - - (ptp->timeset[last_good].host_start & MC_NANOSECOND_MASK); - - /* It is possible that the seconds rolled over between taking + /* Calculate delay from last good sync (host time) to last_time. + * It is possible that the seconds rolled over between taking * the start reading and the last value written by the host. The * timescales are such that a gap of more than one second is never - * expected. + * expected. delta is *not* normalised. */ start_sec = ptp->timeset[last_good].host_start >> MC_NANOSECOND_BITS; last_sec = last_time->ts_real.tv_sec & MC_SECOND_MASK; - if (start_sec != last_sec) { - if (((start_sec + 1) & MC_SECOND_MASK) != last_sec) { - netif_warn(efx, hw, efx->net_dev, - "PTP bad synchronisation seconds\n"); - return -EAGAIN; - } else { - delta.tv_sec = 1; - } - } else { - delta.tv_sec = 0; + if (start_sec != last_sec && + ((start_sec + 1) & MC_SECOND_MASK) != last_sec) { + netif_warn(efx, hw, efx->net_dev, + "PTP bad synchronisation seconds\n"); + return -EAGAIN; } + delta.tv_sec = (last_sec - start_sec) & 1; + delta.tv_nsec = + last_time->ts_real.tv_nsec - + (ptp->timeset[last_good].host_start & MC_NANOSECOND_MASK); + + /* Convert the NIC time at last good sync into kernel time. + * No correction is required - this time is the output of a + * firmware process. + */ + mc_time = ptp->nic_to_kernel_time(ptp->timeset[last_good].major, + ptp->timeset[last_good].minor, 0); + + /* Calculate delay from NIC top of second to last_time */ + delta.tv_nsec += ktime_to_timespec(mc_time).tv_nsec; + /* Set PPS timestamp to match NIC top of second */ ptp->host_time_pps = *last_time; pps_sub_ts(&ptp->host_time_pps, delta); |