[Arm-netbook] device tree not the answer in the ARM world

Scott Sullivan scott at ss.org
Mon May 6 21:57:16 BST 2013

On 05/06/2013 04:02 PM, luke.leighton wrote:
> On Mon, May 6, 2013 at 7:55 PM, Scott Sullivan <scott at ss.org> wrote:
>>   Assuming down the road after the first (or even
>> second) EMOA-68 card is being sold, would you dedicate resources to
>> tackling a UEFI boot environment for future cards? The iMX6 care sounds
>> like a candidate if it already has it as you say.
>   *deep breath*.  hadn't considered the question before now.  let me
> think it logically through.  what's the priority order:
>   1) find a SoC where we know it's going to competitively sell in mass-volume.
>   2) find a way to get through the "pain" barrier of allowing us access
> to it [this will get easier, once there are sales underway].
>   3) stop if they want us to sign GPL-violating NDAs, and go back to 1)
> if they do.
>   4) get hold of hardware schematics.  or find a way to get them at a
> reasonable cost.  if not possible, go back to 1)
>   5) modify the linux kernel for that SoC to get it to support the EOMA
> libs and drivers [this will get easier once there is at least two
> completely different SoCs, preferably with completely different
> instruction sets]


>   so, scott: against that background of tasks, what benefits would "6)
> add a UEFI boot environment" add to that list of priorities?  would it
> *have* to be added, because you could reasonably expect some SATA
> drives to be formatted as UEFI partitions because they'd been made by
> e.g. an x86 EOMA-68 CPU Card's OS.

Ah. So on reflection, I choose UEFI simply because it was already in the 
conversation. It was not a very well thought out choice for my question.

More generally then, and you've started to illuminate some of it, what 
is your road map? What minimum feature set from a boot perspective have 
you considered? (It's okay if this is 'I'll cross that bridge when I 
come to it' answer.)

UEFI at least gives us a working model in which to ask the questions.

I would like to see the day when I can buy one of these cards and it 
boots and I can have my USB DVD rom or PXE boot server on standby and 
it's just a handful of keyboard clicks away from starting an install of 
favourite distro X.

So the more precise question is do you plan to support that kind of boot 
environment in future EMOA-68 products (regardless of what software is 
used to do it)? Step 5 implies to me 'yes, to some degree of yes'.

Clearly the A10 card once simple out of the necessity of bootstrapping.

I see this issue gets a lot easier since as being at the OEM you can 
dictate the firmware/bios/uboot as you like. The buses are discoverable, 
severally limiting the "wonky" design choices down to reusable drivers 
for the I/O boards and quarantined uniqueness within the card which can 
be hidden by said dictated boot code.

Scott Sullivan

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