From: Richard Cochran <richardcochran@gmail.com>
To: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Cc: davem@davemloft.net, Jacob Keller <jacob.e.keller@intel.com>,
netdev@vger.kernel.org, nhorman@redhat.com, sassmann@redhat.com,
Andrew Bowers <andrewx.bowers@intel.com>
Subject: Re: [net-next 06/15] ixgbe: fix PTP SDP pin setup on X540 hardware
Date: Wed, 5 Jun 2019 20:20:50 -0700 [thread overview]
Message-ID: <20190606032050.4uwzcc7rdx3dkw5x@localhost> (raw)
In-Reply-To: <20190605202358.2767-7-jeffrey.t.kirsher@intel.com>
On Wed, Jun 05, 2019 at 01:23:49PM -0700, Jeff Kirsher wrote:
> + * It calculates when the system time will be on an exact second, and then
> + * aligns the start of the PPS signal to that value.
> + *
> + * This works by using the cycle counter shift and mult values in reverse, and
> + * assumes that the values we're shifting will not overflow.
So I guess that this device can't adjust the frequency in hardware,
and that is why the driver uses a timecounter.
BUT your PPS will not be correct. You use the 'mult' to calculate the
future counter time of the PPS, but as soon as the PTP stack adjusts
the frequency (and changes 'mult') the PPS will occur at the wrong
time.
Sorry to say it,
Richard
next prev parent reply other threads:[~2019-06-06 3:20 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-05 20:23 [net-next 00/15][pull request] 10GbE Intel Wired LAN Driver Updates 2019-06-05 Jeff Kirsher
2019-06-05 20:23 ` [net-next 01/15] ixgbe: add tracking of AF_XDP zero-copy state for each queue pair Jeff Kirsher
2019-06-05 20:23 ` [net-next 02/15] ixgbe: remove umem from adapter Jeff Kirsher
2019-06-05 20:23 ` [net-next 03/15] ixgbe: fix AF_XDP tx byte count Jeff Kirsher
2019-06-05 20:23 ` [net-next 04/15] ixgbe: fix AF_XDP tx packet count Jeff Kirsher
2019-06-05 20:23 ` [net-next 05/15] ixgbe: reduce PTP Tx timestamp timeout to 1 second Jeff Kirsher
2019-06-05 20:23 ` [net-next 06/15] ixgbe: fix PTP SDP pin setup on X540 hardware Jeff Kirsher
2019-06-06 3:20 ` Richard Cochran [this message]
2019-06-06 20:37 ` Keller, Jacob E
2019-06-07 3:34 ` Richard Cochran
2019-06-07 17:27 ` Keller, Jacob E
2019-06-05 20:23 ` [net-next 07/15] ixgbe: use 'cc' instead of 'hw_cc' for local variable Jeff Kirsher
2019-06-05 20:23 ` [net-next 08/15] ixgbe: add a kernel documentation comment for ixgbe_ptp_get_ts_config Jeff Kirsher
2019-06-05 20:23 ` [net-next 09/15] net: Add a define for LLDP ethertype Jeff Kirsher
2019-06-05 20:23 ` [net-next 10/15] i40e: Use LLDP ethertype define ETH_P_LLDP Jeff Kirsher
2019-06-05 20:23 ` [net-next 11/15] ixgbe: " Jeff Kirsher
2019-06-05 20:23 ` [net-next 12/15] ice: " Jeff Kirsher
2019-06-05 20:23 ` [net-next 13/15] net: hns3: " Jeff Kirsher
2019-06-05 20:23 ` [net-next 14/15] ixgbe: implement support for SDP/PPS output on X550 hardware Jeff Kirsher
2019-06-05 20:23 ` [net-next 15/15] net: ixgbevf: fix a missing check of ixgbevf_write_msg_read_ack Jeff Kirsher
2019-06-05 23:44 ` [net-next 00/15][pull request] 10GbE Intel Wired LAN Driver Updates 2019-06-05 David Miller
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