simpleImage.XX and large kernels

simpleImage.XX and large kernels

[John Williams]

Hi,

I'm looking at the simpleImage.XXX make target (PPC 405/440), and it
seems that by default the arch/powerpc/boot/wrapper script places the
bootwrapper at 0x400000, effectively setting a limit on the maximum
bootable kernel size.

For various reasons we'd like to be able to put a fairly complete
rootfs as an initramfs, which obviously blows past a 4Mbyte limit very
quickly.  Short of adding a new 'platform' option and associated
hackery through the powerpc/boot Makefiles and wrapper, is there a
quick and clean way I can tell the boot wrapper to link at a higher
address?

Thanks,

John

Re: simpleImage.XX and large kernels

[Wolfgang Denk]

Dear John Williams,

In message <1d3f23371002080247j17138famcf4e4aebc1ae04f5@mail.gmail.com> you wrote:
> 
> I'm looking at the simpleImage.XXX make target (PPC 405/440), and it
> seems that by default the arch/powerpc/boot/wrapper script places the
> bootwrapper at 0x400000, effectively setting a limit on the maximum
> bootable kernel size.
> 
> For various reasons we'd like to be able to put a fairly complete
> rootfs as an initramfs, which obviously blows past a 4Mbyte limit very
> quickly.  Short of adding a new 'platform' option and associated
> hackery through the powerpc/boot Makefiles and wrapper, is there a
> quick and clean way I can tell the boot wrapper to link at a higher
> address?

Is there any specific reason why you want to use simpleImage, instead
of using a normal uImage either bundled with your ramdisk image as a
classic multifile image, or (recommended) as a FIT image?

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de
It's all Klatchian to me.
        - Terry Pratchett & Stephen Briggs, _The Discworld Companion_

Re: simpleImage.XX and large kernels

[John Williams]

Hi Wolfgang,

On Tue, Feb 9, 2010 at 8:48 AM, Wolfgang Denk <wd@denx.de> wrote:
>> I'm looking at the simpleImage.XXX make target (PPC 405/440), and it
>> seems that by default the arch/powerpc/boot/wrapper script places the
>> bootwrapper at 0x400000, effectively setting a limit on the maximum
>> bootable kernel size.
>>
>> For various reasons we'd like to be able to put a fairly complete
>> rootfs as an initramfs, which obviously blows past a 4Mbyte limit very
>> quickly. =A0Short of adding a new 'platform' option and associated
>> hackery through the powerpc/boot Makefiles and wrapper, is there a
>> quick and clean way I can tell the boot wrapper to link at a higher
>> address?
>
> Is there any specific reason why you want to use simpleImage, instead
> of using a normal uImage either bundled with your ramdisk image as a
> classic multifile image, or (recommended) as a FIT image?

Yes, there are a few reasons, though not necessarily very strong ones!
 Although we'll normally be using u-boot, I don't want to make it a
hard requirement.  simpleImage's ability to boot directly with a DTB
already bundled is attractive in this regard.

Another reason is that for compatibility with our MicroBlaze flow
(which also uses a simpleImage target, although a MicroBlaze
simpleImage is actually vmlinux with the DTB stuffed into its own
section).

Also sometimes it's nice to have a single ELF or binary blob we can
just push over JTAG straight to the target.  Having the DTB embedded
simplifies this process, no need to download vmlinux and DTB
separately, setup boot params etc.

I like FIT and think it's an elegant solution, I'm just a bit
reluctant to force its use.  For deeply embedded and flash constrained
systems we sometimes have a requirement to bypass uboot and boot
directly.

I may have to rethink the boot strategy eventually but in the short
term, getting some control over simpleImage as per my original post
would be a good first step.

Regards,

John

Re: simpleImage.XX and large kernels

[David Gibson]

On Mon, Feb 08, 2010 at 08:47:44PM +1000, John Williams wrote:
> Hi,
> 
> I'm looking at the simpleImage.XXX make target (PPC 405/440), and it
> seems that by default the arch/powerpc/boot/wrapper script places the
> bootwrapper at 0x400000, effectively setting a limit on the maximum
> bootable kernel size.
> 
> For various reasons we'd like to be able to put a fairly complete
> rootfs as an initramfs, which obviously blows past a 4Mbyte limit very
> quickly.  Short of adding a new 'platform' option and associated
> hackery through the powerpc/boot Makefiles and wrapper, is there a
> quick and clean way I can tell the boot wrapper to link at a higher
> address?

Not really, although altering the wrapper script to change the link
address is really not difficult.

Having the wrapper automatically adjust the link address based on the
size of the decompressed kernel has been on my todo list for ages, but
it's unlikely I'll get around to implementing it any time soon.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson