On 02.02.2023 20:57:42, Vincent Mailhol wrote:
> On Thu. 2 Feb 2023 at 20:09, Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx> wrote:
> > "The (Re-)Synchronization Jump Width (SJW) defines how far a
> > resynchronization may move the Sample Point inside the limits defined
> > by the Phase Buffer Segments to compensate for edge phase errors." [1]
> >
> > In other words, this means that the SJW parameter controls the CAN
> > controller's tolerance to frequency errors compared to other CAN
> > controllers.
> >
> > If the user space doesn't provide a SJW parameter, the
> > kernel chooses a default value of 1. This has proven to be a good
> > default value for CAN controllers, but no longer for modern
> ^^^^^^^^^^^^^^^
> > controllers.
>
> Are you missing a word here? You oppose CAN controllers to modern
> ones.
>
> I think the point is Classical CAN only controllers vs. CAN-FD
> controllers. A CAN-FD controller is able to sample at bitrates up to 5
> or 8 Mbits and have maximum bitimming values five or eight times the
> ones of a Classical CAN only controller (which is only capable of
> sampling 1 Mbits).
>
> I propose this instead:
>
> This has proven to be a good default value for Classical CAN
> controllers, but no longer for modern CAN-FD ones.
The difference that matters here is not that the controllers support
CAN-FD, but that they have a much greater max tseg{1,2} compared to the
sja1000. But that's only the case on CAN-FD controller.
Will change the description as you proposed!
Thanks,
Marc
--
Pengutronix e.K. | Marc Kleine-Budde |
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