building RaspPi Images

[Warner Losh]

On Feb 10, 2013, at 12:32 AM, Andrew Turner wrote:

> On Sat, 9 Feb 2013 23:03:38 -0800
> Tim Kientzle <tim at kientzle.com> wrote:
> 
>> On Feb 9, 2013, at 10:20 PM, Brett Wynkoop wrote:
>>> 
>>> I was thinking that we should be able to generate a generic image
>>> that will boot on both the Pi and the Bone.  Maybe a config file
>>> that includes the needed drivers for both boards.
>> 
>> I've thought about this and believe it is pretty routine,
>> though I've not had time to actually try implementing it.
>> 
>> This specific combination is simplified by the fact
>> that the boot bits are so different, so you can just
>> put them all on the same SD card image.
>> 
>> There are a few pieces you'll need to work through:
>>  1. An MSDOS partition with all the boot bits from both systems
>>  2. A kernel with all of the drivers for both systems
>>  3. ubldr will need to identify the board somehow
>>  4. ubldr will need to obtain the correct FDT
> 5. Update the kernel to allow it to be built for multiple boards. You
> will need to at least fix:
> - locore.S generates a fixed VA -> PA map, it's not too hard to fix
>   this, I've looked into it but don't have the time to get it into a
>   usable state.

Aren't there also a number of VA/PA translations elsewhere that are also hard coded via various #defines...

> - initarm calls a number of functions that have are implemented on a
>   per SoC family case.

FDT can help us here. We can get the SoC from it.

> - Update the IRQ mask/unmask/next irq functions to allow multiple
>   implementations and pick the correct one on boot.
> - Ditto for DELAY, DMA, reset, etc functions.

I started on this at one point...

> I would suggest the first step is to get a kernel that can boot on the
> BeagleBone and PandaBoard. As they both have Ti CPUs they are similar
> enough we could skip some of the items in my list as they are already
> using a common SoC specific code base.

I've also been pushing this for different Atmel boards as well, but there isn't even FDT support for it just yet...

Warner