linux-kernel - RE: [Intel-wired-lan] [PATCH net-next v3 1/2] e1000e: factor out systim sanitization

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Date:	Thu, 4 Aug 2016 19:34:35 +0000
From:	"Brown, Aaron F" <aaron.f.brown@...el.com>
To:	"Woodford, Timothy W." <Timothy.Woodford@...apl.edu>,
	"Avargil, Raanan" <raanan.avargil@...el.com>,
	Jarod Wilson <jarod@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Hall, Christopher S" <christopher.s.hall@...el.com>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>
Subject: RE: [Intel-wired-lan] [PATCH net-next v3 1/2] e1000e: factor out
 systim	sanitization

> From: Intel-wired-lan [mailto:intel-wired-lan-bounces@...ts.osuosl.org] On
> Behalf Of Woodford, Timothy W.
> Sent: Friday, July 29, 2016 7:41 AM
> To: Woodford, Timothy W. <Timothy.Woodford@...apl.edu>; Avargil,
> Raanan <raanan.avargil@...el.com>; Jarod Wilson <jarod@...hat.com>;
> linux-kernel@...r.kernel.org; Hall, Christopher S
> <christopher.s.hall@...el.com>
> Cc: netdev@...r.kernel.org; intel-wired-lan@...ts.osuosl.org
> Subject: Re: [Intel-wired-lan] [PATCH net-next v3 1/2] e1000e: factor out
> systim sanitization
> 
> >>> This is prepatory work for an expanding list of adapter families that have
> occasional ~10 hour clock jumps when being used for PTP. Factor out the
> sanitization function and convert to using a feature (bug) flag, per suggestion
> from Jesse Brandeburg.
> >>>
> >>> Littering functional code with device-specific checks is much messier than
> simply checking a flag, and having device-specific init set flags as needed.
> >>> There are probably a number of other cases in the e1000e code that
> could/should be converted similarly.
> >>
> >> Looks ok to me.
> >> Adding Chris who asked what happens if we reach the max retry counter
> (E1000_MAX_82574_SYSTIM_REREAD)?
> >> This counter is set to 50.
> >> Can you, for testing purposes, decreased this value (or even set it to 0)
> and see what happens?
> >  I'll set the max retry counter to 1 and run an overnight test to see what
> happens.
> 
> After running with this configuration for about 36 hours, I haven't seen any
> timing jumps.  Either this configuration eliminates the error, or it makes it
> significantly less likely to occur.
> 
> Tim Woodford

Feel free to throw a Tested-by: on it if you like.  Not a big deal either way, I managed to get enough cycles in on it I'm pretty happy with it as well.

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