Allwinner A20 (dual core Cortex A7)

[Andrew Wafaa]

On 01-08-2013 03:09, Warner Losh wrote:
> On Jul 31, 2013, at 8:05 PM, Ganbold Tsagaankhuu wrote:
> 
>> Hi Hans and all,
>> 
>> Just tried to run freebsd on Cubieboard2 with some minor modification 
>> to
>> timer code for A10.
>> However after detecting usb it just stops near "Root mount waiting 
>> for:
>> usbus1". I see light on usb stick. System supposed to mount rootfs 
>> from usb
>> stick and usb stick was prepared by using Tim's crochet script.
>> 
>> Dmesg: http://pastebin.com/7WkkExN2
>> 
>> What problem it could be? Any suggestions?
> 
> Clocks. I'd make sure that all the clocks are spun up correctly. On
> other ARM cores if you do this wrong (and it tends to be different for
> different SoCs), then you get weird usb behavior.
> 
> Interrupts. When interrupts aren't routed correctly, usb misbehaves
> (although not that badly).
> 
> Cache. Maybe the cache lines are bigger (though doubtful, since the
> A10 has an A7 inside, iirc). If so, then USB_DMA_ALIGNMENT may need to
> be bumped.
> 

One of the big differences with the A20 vs the A10 is the Interrupt 
Controller, as the new Cortex-A7 based devices are now connected to a 
standard ARM GIC rather than some home grown thing on the older 
Cortex-A8s. There's a strong chance that it could be causing you issues 
if not supported properly, this is certainly the case on other OSes.

Regards,

Andy