netdev - Re: [PATCH net V4 2/2] igb: offer a PTP Hardware Clock instead of the timecompare method

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Date:	Mon, 26 Mar 2012 11:07:40 -0400
From:	chetan loke <loke.chetan@...il.com>
To:	Richard Cochran <richardcochran@...il.com>
Cc:	"Keller, Jacob E" <jacob.e.keller@...el.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"e1000-devel@...ts.sourceforge.net" 
	<e1000-devel@...ts.sourceforge.net>,
	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	"Ronciak, John" <john.ronciak@...el.com>,
	"john.stultz@...aro.org" <john.stultz@...aro.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>
Subject: Re: [PATCH net V4 2/2] igb: offer a PTP Hardware Clock instead of the
 timecompare method

On Sat, Mar 24, 2012 at 2:51 AM, Richard Cochran
<richardcochran@...il.com> wrote:
> On Fri, Mar 23, 2012 at 03:39:08PM -0400, chetan loke wrote:
>>
>> So, how is it working today? Because we could have tx and rx
>> completions on different CPUs. Is it not possible to have the
>> following race today - between timecompare_update->timecompare_offset
>> -> timecounter_readdelta of say Rx and timecounter_cyc2time from Tx?
>
> I works (in the igb) because of the spinlock. You know, that thing
> that you are so against using.
>

I meant, was there a lock before the PHC functionality in igb?

>
>> How about rate limiting at the PHC class driver level? And then it
>> will work across the board for all the adapters at the device level.
>
> No, don't go there. Enough bikeshedding already. If you have a serious

can a user without root privileges use get/adj/set time ioctls for the
PHC functionality?


> Thanks,
> Richard

Chetan
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