Re: AW: Receiving messages issue

[Marc Kleine-Budde <mkl@pengutronix.de>]

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On 07/05/2013 12:07 PM, Luka Rahne wrote:
> I was able to include this driver in my project but first test shows
> that there is no significant improvement.
> 
> I also had to patch driver in order to compile and work.
> Can someone more experienced check patch for some fatal issues?

Just the tx_bytes calculation isn't correct, see inline. But that will
not cause bad performance.

>  Testing results:
> Test -> sending 520 messages in total (each burst had 65 unique ID
> messages of length 8 ) @ 100k baud.
> USB-PEAK-CAN used for listening only, confirms all messages on sent bus.
> 
> New spi async drivers mcp2515.c had 3% packet loss and stable stock
> driver mcp251x.c included in kernel 3.0.81 had 5% losts messages.

That's about 40% less packet loss.

> Decreasing baud on 50k had no packet loss for handling packets of
> length 8 bytes (stock driver), but there is still issue on receiving
> messages of length 0. (tested with stock driver only)
> As expected shorter messages generates more interrupts, since they
> takes less time to transfer.
> 
> Does anyone has any ideas what should I try, because I dont have lot
> more ideas to try with.

If I remember correct the i.mx spi driver uses a workqueue internally
and in newer kernels there isn't a kthread directly associated with that
workqueue. You can patch the spi driver to create a special kthread
based workqueue, which you can boost in priority via chrt in userspace
later.

> Is there any chip on market that has more than few RX buffers and can
> better handle high baud bus?

If you have access to the data and address bus on your processor you can
attach an sja1000 (you need a bunch of level shifters, too), that works
pretty good. Another option is to use some USB based CAN adapter.

regards,
Marc

-- 
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