ARM Machine SoC I/O setup and PAD initialization code

[Magnus Damm]

On Thu, Jul 22, 2010 at 5:49 PM, Eric Miao <eric.y.miao at gmail.com> wrote:
> On Thu, Jul 22, 2010 at 10:38 AM, Magnus Damm <magnus.damm at gmail.com> wrote:
>> On Thu, Jul 22, 2010 at 4:29 PM, Simon Horman <horms at verge.net.au> wrote:
>>> On Thu, Jul 22, 2010 at 08:20:34AM +0100, Russell King - ARM Linux wrote:
>>>> On Thu, Jul 22, 2010 at 11:32:53AM +0900, Simon Horman wrote:
>>>> > Would it be feasible to  use Linux + kexec as the boot loader as
>>>> > a long term solution to fixing boot loaders by eliminating them?
>>>>
>>>> So what you're proposing is that a broken boot loader should boot a
>>>> version of Linux to fix the pin MUX, which then kexecs a kernel which
>>>> doesn't have that code?
>>>>
>>>> What's the point of that - when the first kernel will be able to run
>>>> the system?
>>>
>>> Ok, point taken, its impossible to remove the boot loaders.
>>
>> I disagree. We already use upstream Linux as a boot loader on SuperH.
>>
>> For ARM and other architectures check out the ELC2010 presentation by
>> Greg Ungerer here:
>> http://elinux.org/images/7/7b/LinuxWithoutABootLoader.pdf
>>
>> For SH and a more zoomed our perspective have a look at my presentation:
>> http://elinux.org/images/2/2f/ELC-2010-Damm-Kexec.pdf
>>
>
> I agree with Magnus, that kernel as a bootloader is a good idea to go.
>
> And the kexecboot works awesome on my zaurus, I like that very much
> instead of flashing my device with a series of awkward steps.

Good to hear!

> Looking into shmobile, there are some specially customized _defconfig
> to support that. More _defconfig in ARM might not be a good idea, but I
> guess we can solve that in a different way though.

On SuperH (arch/sh), the multiple defconfigs are there to give users a
known working boot loader configuration. They may not be there for
long though.

To build a kernel that can be burned into the reset vector in NOR
flash on SuperH, you simply use the romImage target instead of zImage
or uImage. The romImage target makes sure low level setup code (memory
setup etc) is included in the kernel image.

I recently got MMC boot working on SuperH, so by selecting
CONFIG_ROMIMAGE_MMCIF=y you can now build a romImage that can be dd:ed
into an MMC card and booted straight by the MASK ROM. Nothing ground
breaking - but at least it's available upstream. I'd like to share
parts of that code with ARM SH-Mobile, but I still have not figured
out how to integrate it cleanly on ARM.

Cheers,

/ magnus