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From: "Matthias Weißer" <m.weisser.m@gmail.com>
To: Oliver Hartkopp <socketcan@hartkopp.net>, linux-can@vger.kernel.org
Subject: Re: sjw in can_calc_bittiming
Date: Wed, 3 Nov 2021 08:12:34 +0100	[thread overview]
Message-ID: <CAO8h3eEijXsgTN0hyxuCuhDms=z-W_8hj1UHWV3544HugsuoPA@mail.gmail.com> (raw)
In-Reply-To: <0a539c49-b92e-892e-5848-613ff745c283@hartkopp.net>

Hi Oliver

Thanks for your answer.

Am Di., 2. Nov. 2021 um 16:36 Uhr schrieb Oliver Hartkopp
<socketcan@hartkopp.net>:
>
> > We can fix this quite easily by specifying a higher sjw value.
>
> You can specify the sjw value with the ip command (for CAN FD there is
> also a dsjw). And IIRC you can set it to the max. value for your CAN
> controller if you define sjw to be 4.

I know that and this is my current solution. And I am totally happy with that.
Sorry if this wasn't clear in my original message.

My question was if it makes sense to change the default in can_calc_bittiming()
to something more adaptive than just 1 depending on the total number of tq.
This may prevent others from hitting the same problem as I did.

If you can take some time and rethink my original question that would be great

> > Wouldn't it make sense to increase sjw in can_calc_bittiming() to something
> > like 5% of the total time quanta? This may increase the reliability of the CAN
> > network when there are differences in the bitrates of the single members. Are
> > there any arguments against such an arbitrary selection of sjw?

Regards

Matthias

  parent reply	other threads:[~2021-11-03  7:12 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-02 15:03 sjw in can_calc_bittiming Matthias Weißer
2021-11-02 15:36 ` Oliver Hartkopp
2021-11-02 15:59   ` Wolfgang Grandegger
2021-11-03  7:12   ` Matthias Weißer [this message]
2021-11-05 12:07 ` Marc Kleine-Budde

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