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Re: [PATCH 8/8] LinuxPPS: pps_gen_parport: Add check for bad clocksource.

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  Re: [PATCH 8/8] LinuxPPS: pps_gen_parport: Add check for bad  clocksource. Alexander Gerasiov <gq@cs.msu.su> - 2017-03-04 10:40 +0100
    Re: [PATCH 8/8] LinuxPPS: pps_gen_parport: Add check for bad  clocksource. Rodolfo Giometti <giometti@enneenne.com> - 2017-03-04 14:30 +0100

#1592438 — Re: [PATCH 8/8] LinuxPPS: pps_gen_parport: Add check for bad clocksource.

Hello Rodolfo,

I should say, that I found this solution is not the best. For example on
high speed PCs (I think over 3GHz) 5 iteration is not enough and module
stops working after several hours. That makes it not user-friendly,
cause user had to calibrate and set failure_iterations manually.

It would be better to use pre-measured loops_per_jiffy (from delay.h)
some way.

On Sat, 4 Mar 2017 08:44:03 +0100
Rodolfo Giometti <giometti@enneenne.com> wrote:

> On 02/15/17 15:31, Andrey Drobyshev wrote:
> > From: Nikita Edward Baruzdin <nebaruzdin@gmail.com>
> >
> > This commit is supposed to resolve the issue with hard lockups on
> > systems using jiffies as their clock source. Namely, it sets limits
> > on number of iterations clock source may remain unchanged (i. e.
> > not being updated for one reason or another, as it is with jiffies
> > clock source), and on unsuccessful getnstimeofday() polls as well.
> > In case limit is reached, we consider clock source incompatible
> > with this driver or unstable.
> >
> > Considering this issue to be fixed, un-BROKEN pps_gen_parport.
> >
> > For explanation of the problem see this thread on lkml:
> > https://lkml.org/lkml/2011/2/18/310
> >
> > Signed-off-by: Nikita Edward Baruzdin <nebaruzdin@lvk.cs.msu.su>
> > Signed-off-by: Alexander GQ Gerasiov <gq@cs.msu.su>  
> 
> Acked-by: Rodolfo Giometti <giometti@enneenne.com>



-- 
Best regards,
 Alexander Gerasiov

 Contacts:
 e-mail: gq@cs.msu.su  Homepage: http://gerasiov.net  Skype: gerasiov
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#1592497

On 03/04/17 10:19, Alexander Gerasiov wrote:
> Hello Rodolfo,
>
> I should say, that I found this solution is not the best. For example on
> high speed PCs (I think over 3GHz) 5 iteration is not enough and module
> stops working after several hours. That makes it not user-friendly,
> cause user had to calibrate and set failure_iterations manually.
>
> It would be better to use pre-measured loops_per_jiffy (from delay.h)
> some way.

I see... however I cannot test the patch so if you tried it and you noticed 
these issues we should consider to add it but with the experimental warning?

Ciao,

Rodolfo

-- 

HCE Engineering                      e-mail: giometti@hce-engineering.com
GNU/Linux Solutions                          giometti@enneenne.com
Linux Device Driver                          giometti@linux.it
Embedded Systems                     phone:  +39 349 2432127
UNIX programming                     skype:  rodolfo.giometti
Cosino Project - the quick prototyping embedded system - www.cosino.io
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