Re: Problems in the DaVinci EMAC driver & AM35xx?

Kevin Hilman
2012-06-28T17:56:04Z

CF Adad <cfadad@rocketmail.com> writes:

[...]

> I bring these questions here, as the crash's call stack shares so many
> similarities to the "SLAB crash" discussed
> "http://thread.gmane.org/gmane.linux.ports.arm.omap/78039/", that I
> think they're related.  At the very least, the EMAC to EMAC
> performance issues we have always seen are troubling.  IMHO, clearly
> the EMAC driver is doing something a little questionable.

I don't know about the crash, but the EMAC performance issues are known.

Basically, the EMAC on the AM3xxx is not wakeup capable. Meaning that
if you enter idle, and EMAC interrupt will not wake the system. The
system will not wake until another wakeup-capable device (e.g. timer)
goes off.

To see if this is causing your problems, add 'nohlt' to your kernel
command line. This will prevent the SoC from ever entering idle, so
your EMAC interrupt latency will drop significantly.

Kevin