On Wed, Oct 13, 2010 at 12:01:18PM +0200, Marc Kleine-Budde wrote:
>
> On 10/13/2010 11:46 AM, Wolfgang Grandegger wrote:
> >>> I'm following the discussion and realized that it will not work for
> >>> devices doing the local loopback in hardware, like the flexcan
> >>> controller.
> >>
> >> What is actually the advantage of using hardware loopback? One can
> >> always quit using it and use Tx interrupt for self reception ...
>
> ...from my other mail:
>
> I think we (the socketcan people) originally thought it's a better
> solution to loop the CAN frames back in hardware (if available), as it
> represents what's happening on the wire far better than software
> loopback.
>
> > Hey, we care about overhead ;-). CAN can cause high interrupt loads,
> > especially at 1 MB/s.
>
> On the flexcan, we use (currently) the hardware loopback. So a TX'ed CAN
> frame generates a TX-complete interrupt, which we need for the
> netif_wake_queue(). And it also generates a RX-interrupt due to the
> hardware loopback.
>
Do I understand well that you didn't do can_put_echo_skb() etc?
FYI, I'm just trying to understand what exactly is meant by
'hardware' & 'software' loopback.
>
> cheers, Marc
Kurt
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