On 21.06.2021 09:24:31, Fabio Estevam wrote:
> > The imx SPI driver has quite some overhead, when it comes to small SPI
> > transfers. The mcp251fd driver performs much better with the SPI IP
> > cores on the raspi, which have quite good optimized drivers.
> >
> > Hook up a scope to the SPI's clock and chip select lines of the imx,
> > you'll see the time between end of transfer until the chip select is
> > inactive is longer than the SPI transfer itself.
> >
> > I expect most bang for the buck can be archived by adding an IRQ less
> > busy polling transfer mode, which kicks in below a certain SPI transfer
> > length.
> >
> > On the mcp251xfd driver side, there is some room for optimization. The
> > basic idea is to reduce the number of SPI transfers by combining several
> > reads into one transfer. This can be done in some places.
> >
> > For peak loads in CAN-2.0 mode it would be interesting to make use of
> > the remaining RAM for a 2nd FIFO.
> 
> Thanks for your reply.
> 
> I do see some RCU related errors every time the application is launched:

[...]

> Any ideas how these RCU errors could be fixed?

Can you test if
https://lore.kernel.org/r/20210621123436.2897023-1-mkl@pengutronix.de
fixes your problem? We still have to check if lockdep complains...

regards,
Marc

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