BCM2836 (Raspberry Pi 2) port

Eric Anholt eric at anholt.net
Fri Apr 24 11:41:38 PDT 2015

Stephen Warren <swarren at wwwdotorg.org> writes:

> On 04/21/2015 12:09 PM, Eric Anholt wrote:
>> This is my first submission of a Raspberry Pi 2 port.  It can be found
>> at https://github.com/anholt/linux/tree/bcm2836
>> I'm using the 2835 interrupt controller support, without adding the
>> checks for ARM local interrupts first.  That means no support for IPIs
>> (and thus no SMP), no PMU events, and no local timer (I'm using the
>> same 2835 peripheral one).
>> It supports a similar featureset to Pi 1 at this point.  Serial and SD
>> cards work.  Just one CPU supported.  USB (ethernet) works if you use
>> U-Boot, or my mailbox series
>> (https://github.com/anholt/linux/tree/bcm2836-mbox).
> I can't quite get this to work. I think what's happening is that U-Boot
> is over-writing the location of the code/data that the CPU1..3 pin loop
> uses. Do you know what that address is so I can confirm that?
> I suspect this because when I load the kernel/DT in U-Boot, or when I
> jump to the kernel to boot it, I see lots of extra duplicated characters
> on the UART, like all 4 CPUs are booting Linux. For example:

Oops, I was just extrapolating that U-Boot would work.  I've quit using
it because of the extra configuration work (particularly the compiled
text files for the boot scripts).

I haven't looked into how SMP works, because I don't have the interrupt
support necessary yet (bcm2836-irq branch for hacks in that direction).

And in further testing, the USB is actually not working and I'm not sure
what gave me the idea that it was.
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