netdev - Re: [PATCH net-next v2 1/8] net-timestamp: explicit SO

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Date:	Mon, 07 Jul 2014 14:08:57 -0700
From:	Chad Reese <kreese@...ium.com>
To:	Richard Cochran <richardcochran@...il.com>
CC:	Willem de Bruijn <willemb@...gle.com>, netdev@...r.kernel.org,
	David Miller <davem@...emloft.net>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Stephen Hemminger <stephen@...workplumber.org>,
	Chad Reese <kreese@...iumnetworks.com>,
	David Daney <david.daney@...ium.com>
Subject: Re: [PATCH net-next v2 1/8] net-timestamp: explicit SO_TIMESTAMPING
 ancillary data struct

On 07/07/2014 01:18 PM, Richard Cochran wrote:
> On Mon, Jul 07, 2014 at 12:44:44PM -0700, Chad Reese wrote:
>>
>> For Octeon, you can optionally use the hardware timestamp as the
>> system clock reference. Most people don't, but it is the only way to
>> get the system time to be accurate. 1588 can synchronize two Octeon
>> boards to less than 1ns for the hardware timer. The Linux software
>> timers is always farther off.
>
> Did you mean 1us ?

No, it was 1ns. Who would go through all this effort if all you wanted 
was 1us?  Our requirement was within 20ns, but me managed to get 1ns 
with a lab setup. We had to be careful that the scope probes used in the 
measurement were the same length.

Chad

-- 

Chad Reese <kreese@...ium.com>
Cavium Networks
Phone: 408 - 943 - 7183
Cell: 321 - 438 - 7753

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