Re: [PATCH v2 14/17] can: bittiming: can_sjw_set_default(): use Phase Seg2 / 2 as default for SJW

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On 02.02.2023 13:07:38, Marc Kleine-Budde wrote:
> 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!

There are no other changes on this series, I've fixed the patch
description as suggested. I'll take this series without resending it.

Thanks again for the review!

regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

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