Re: [Linuxptp-users] Hardware PTP clock synchronization

[Richard C. <ric...@gm...>]

On Sat, Aug 03, 2013 at 05:33:29PM +0300, Alex Gavrilov wrote:

> 1 time hardware clock was synchronized, and in the application i see
> what time "/dev/ptp0" synchronizes (through clock_gettime). But again
> it did not work.

What did not work?

> I also thought that if the synchronization happens
> sometimes, even with errors, we would arrange this option. But the
> synchronization is no longer happening, how much we try to.

Are you talking about the Linux system time?  If so, you can
sychronize it to /dev/ptp0 using the phc2sys program.

> In what could be the reason? Switch sync time is too long (2 sec).
> My boss does not believe that the Intel certified card can not be
> fully tested and have a hardware error.
 
Hardware ships with bugs. It is a fact of life.

When bugs are discovered, an erratum is published that tells you that
the bug does exist. Intel calls their errata "Specification Update".
You should look if there is one for the 82576.

Even if none have been published, that doesn't mean there aren't
hardware bugs. You and your boss might find this document interesting.
It describes an Intel PTP hardware implementation with bugs.

http://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/ixp4xx-product-line-network-processors-spec-update.pdf

Look especially at Item #40 on page 39:

   40. IEEE-1588 Time Sync Lock-up Fails to Time-Stamp a Second PTP Message

   Problem:     A lock-up condition has been identified in the
                IEEE-1588 Time Sync block that prevents all subsequent
                messages form being time-stamped. It occurs when a
                message has been time-stamped and the registers are
                locked, after which - if a new message comes in before
                the previous time stamp is read and the lock bit is
                cleared - the Time Sync block enters a lock-up
                condition and prevents all furthers messages from
                being time-stamped. This occurs for both received and
                transmitted messages.

   Implication: Under very typical usage scenarios, the IEEE-1588 unit
                can lock up and will not capture time stamps after the
                initial one is locked.

   Workaround:  If IEEE-1588 functionality is required, it must be
                implemented with external hardware.

This says that PTP function in the silicon is totally useless.

> Can I get an official response from Intel about this card (or any
> official response to convince my boss, they 2 months not responding).

Maybe you can, but don't hold your breath.

Thanks,
Richard