Re: 2.6.23-rc3, freeze during gadget ether usage

> I'm using 2.6.23-rc3 with AT91RM9200 and USB gadget ether. My device is 
> essentially the same as an AT91RM9200DK.
>
> I'm doing a test where I continuously plug and unplug the device from
> a Windows XP machine. The driver on the Windows side is the MCCI CDC-SAFE
> driver.
>
> After a random number of dis/connections my Linux system freezes. There
> are no errors or warning logs, and no "oops!". Eventually the watchdog
> times out and it resets. If I disable the watchdog timer, it will never
> leave this frozen state.

If it's like a DK, that means you have both a VBUS-sense irq and
an external D+ pullup, right?

Try ignoring the VBUS sensing IRQ and see if that affects anything.

I recall the code in that area being a bit twitchey, and some changes
went in a while back (a year or more) that didn't have as much testing
as I'd have liked.  (I have an rm9200 board without VBUS-sense...)


> Any hints? is there something specific that I should look for? Has
> anyone seen this sort of behaviour before?

Not recently, but ISTR seeing issues like that ages ago on a DK.

What it's trying to do is use the absense of VBUS power to power
down as much as it possibly can ... all its clocks, and thus
usually PLLB, plus the transceiver.  (That saves around 5 mA.)

Since the controller is dealing with two clock domains (the USB
domain at 48 MHz, and the CPU bus clock normally at something else),
there can be glitches with operations which cross clock domains.
That's easy enough to goof up in hardware -- not enough synch to
cope with all the little races -- and it's rarely clear how the
software should try to defend itself..


> Should I wait for the proper 2.6.23 stable release?

I don't think anything in the patch queue should affect that.

- Dave


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