linuxptp-users

[Linuxptp-users] Can phc2sys sync two physical clocks?

[John H. <jhu...@no...>]

As I understand it the phc2sys package is generally responsible for 
synchronizing a physical clock to the system time or vice versa.  Is it 
possible to use the package to synchronize two physical clocks?

In my case I'm looking to take wall time as determined by a NIC that 
supports hardware timestamping using the ptp4l package and write that 
time to a DIO card that has its own internal clock.  We were using a 
previous version of the DIO card which had an ethernet input and was 
capable of synchronizing itself to PTP. The new version lacks that 
feature.  In case it helps the card in question is a Spectracom TSync 
PCIe; we are using the cards input time stamping, and output match time 
features.

My hope is that you, who are more knowledgeable on time than I, might 
have suggestions on the best way to synchronize the card's time with the 
incoming PTP time.  Is my best bet to read the system time via 
std::chrono::system_clock::now() and then write that time to my DIO 
card.  Is there some way to read the current time directly from 
/dev/ptp0?  Is there an easy way to extend phc2sys to write the time to 
my DIO card?

Thanks in advance for any suggestions.

-- 
-john

To be or not to be, that is the question
                 2b || !2b
(0b10)*(0b1100010) || !(0b10)*(0b1100010)
         0b11000100 || !0b11000100
         0b11000100 ||  0b00111011
                0b11111111
255, that is the answer.

Re: [Linuxptp-users] Can phc2sys sync two physical clocks?

[Ledda W. E. <Wil...@it...>]

In general phch2sys can be used to synchronize two “POSIX” clocks. So you can synchronize system clock with /dev/ptp0, /dev/ptp0 with system clock, or e.g.  /dev/ptp0 with /dev/ptp1 if you have two ptp devices.

For sure you can easily get the time from /dev/ptp0. You can look into the ptp4l/ph2sys source code to find how you can open the device to get its clock_id and read its time with a standard clock_gettime.

As far as I know, to control the clock of your DIO from phc2sys you need to “expose” the clock implementing the PHC kernel interface in the driver…

HTH
William


From: John Hubbard [mailto:jhu...@no...]
Sent: 17 March 2016 23:03
To: lin...@li...
Subject: [Linuxptp-users] Can phc2sys sync two physical clocks?

As I understand it the phc2sys package is generally responsible for synchronizing a physical clock to the system time or vice versa.  Is it possible to use the package to synchronize two physical clocks?

In my case I'm looking to take wall time as determined by a NIC that supports hardware timestamping using the ptp4l package and write that time to a DIO card that has its own internal clock.  We were using a previous version of the DIO card which had an ethernet input and was capable of synchronizing itself to PTP.  The new version lacks that feature.  In case it helps the card in question is a Spectracom TSync PCIe; we are using the cards input time stamping, and output match time features.

My hope is that you, who are more knowledgeable on time than I, might have suggestions on the best way to synchronize the card's time with the incoming PTP time.  Is my best bet to read the system time via std::chrono::system_clock::now() and then write that time to my DIO card.  Is there some way to read the current time directly from /dev/ptp0?  Is there an easy way to extend phc2sys to write the time to my DIO card?

Thanks in advance for any suggestions.

--

-john



To be or not to be, that is the question

                2b || !2b

(0b10)*(0b1100010) || !(0b10)*(0b1100010)

        0b11000100 || !0b11000100

        0b11000100 ||  0b00111011

               0b11111111

255, that is the answer.

Re: [Linuxptp-users] Can phc2sys sync two physical clocks?

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

On Fri, Mar 18, 2016 at 08:07:10AM +0000, Ledda William EXT wrote:

> As far as I know, to control the clock of your DIO from phc2sys you
> need to “expose” the clock implementing the PHC kernel interface in
> the driver…

Yes, but the DIO card doesn't need to be a PHC (= PTP Hardware Clock),
it only needs to be a "Dynamic" POSIX clock.

The driver interface is defined in include/linux/posix-clock.h in the
Linux kernel sources.  Right now, the only driver implementing this
feature is the PHC layer (see drivers/ptp/ptp_clock.c).

So the DIO card needs a device driver that implements a dynamic clock.
In addition to getting and setting the time, the card and driver will
need to support frequency adjustment.

Once you have the DIO driver, then the phc2sys program will work
without modifications.

HTH
Richard