Re: [Linuxptp-users] HWTSTAMP_TX_ONESTEP_SYNC vs HWTSTAMP_TX_ON

[Miroslav L. <mli...@re...>]

On Tue, Jul 30, 2013 at 10:32:50AM +0200, Richard Cochran wrote:
> On Tue, Jul 30, 2013 at 10:12:51AM +0200, Miroslav Lichvar wrote:
> > 
> > Just curious, would it be possible to use the launch time feature of
> > i210 to do onestep in software?
> 
> I thought about this, but it might be tricky:
> 
> 1. user sends an event message.
> 2. network stack passes skb to driver.
> 3. driver picks a future time to send, updates the skb data.
> 4. driver places skb into the special queue.
> 
> The tricky part is to pick a safe future transmit time.

I was thinking about collecting statistics for successful delays and
aiming for a percentage. I'm wondering what is the maximum packet rate
one can get with it. Also, if it's not a reply, it might be necessary
to read the PTP clock over the bus to calculate the launch time or
perhaps it could be derived from the system clock.

-- 
Miroslav Lichvar