[U-Boot] [PATCH 2/3] x86: Enable ICH6 GPIO controller for coreboot

[Graeme Russ]

Hi Simon,

On 10/21/2012 10:51 AM, Simon Glass wrote:
> Hi Graeme,
> 
> On Sat, Oct 20, 2012 at 3:57 PM, Graeme Russ <graeme.russ at gmail.com> wrote:
>> Hi Simon,
>>
>> On Oct 21, 2012 9:32 AM, "Simon Glass" <sjg at chromium.org> wrote:
>>>
>>> Hi Graeme,
>>>
>>> On Sat, Oct 20, 2012 at 3:22 PM, Graeme Russ <graeme.russ at gmail.com>
>>> wrote:
>>>> Hi Simon,
>>>>
>>>> On Oct 21, 2012 8:45 AM, "Simon Glass" <sjg at chromium.org> wrote:
>>>>>
>>>>> Coreboot uses this controller to implement GPIO access.
>>>>
>>>> All coreboot supported boards, or just the ones you are dealing with
>>>> ATM?
>>>>
>>>> To give you some perspective, I'm working on n AMD E350 based board.
>>>> Does it
>>>> have ICH6 GPIO?
>>>>
>>>> I've come to a conclusion that U-Boot as a coreboot payload will be the
>>>> norm
>>>> for the foreseeable futre, so let's make board specific support as
>>>> flexible
>>>> as possible.
>>>
>>> If that's the case then we might need a little rethink. Are you saying
>>> that coreboot might become the only board, or that the coreboot
>>> functions should move into generic x86 code?
>>
>> Make coreboot a SoC and then have individual board configs which use it
> 
> Hmmm ok. How is that going to play with real SOCs when x86 gets them?

True. Could we just have a coreboot library and and board that is
chainloading U-Boot from coreboot simply define CONFIG_X86_COREBOOT?

>>> I am not sure about your board GPIO, but you could test it I suppose.
>>>
>>> On ARM we use the fdt to describe what peripherals are there and what
>>> are not. I suppose we could do the same thing here.
>>
>> I was wondering how to pass more info from coreboot to U-Boot, maybe we can
>> use FDT
> 
> We have been using that, but I think coreboot wants to stop. Coreboot
> has its own tag-based data structure.

Linux supports FDT, U-Boot supports FDT - Why not FDT from all the way through?

> But what I mean is that you provide an fdt for your board which
> describes the GPIO controller. So not something that coreboot deals
> with, just something for the U-Boot GPIO drivers to look at.

Remember, U-Boot will have the hardware support hard-coded - there will not
bee support for arbitrary hardware. Your coreboot and U-Boot images must,
to some extent, be a pigeon pair.

My concern is, who is initialising what hardware? U-Boot should not
re-initialise hardware already initialised by coreboot. I see FDT as a way
of passing the 'I have already initialised xxx' from coreboot to U-Boot.

Regards,

Graeme