[U-Boot] fastboot boot base address behaviour

[Maxime Ripard]

On Wed, Apr 22, 2015 at 05:56:23PM +0200, Marek Vasut wrote:
> > I've been trying to use fastboot (and especially the boot command) on
> > sunxi recently, and got it to work pretty fine (apart from PSCI, but
> > that's another story).
> > 
> > The only thing that worries me a bit is that by default, both the
> > fastboot tool and mkbootimg will generate an image with the kernel
> > address set to 0x10008000.
> 
> Looks like MX6 DRAM base address, so this should definitelly not be
> fixed to this address here. The +0x8000 offset is the kernel load
> offset.
> 
> > While it might work on some targets, it obviously doesn't on the
> > Allwinner SoCs that most of the time have the RAM mapped to 0x4000000,
> > which result in the kernel being relocated to some address that is not
> > in RAM, failing badly.
> 
> Yep.
> 
> > I would expect U-Boot to relocate the kernel to some reasonable
> > address, and not try to do something dumb by actually trusting
> > completely the boot image.
> 
> I'd expect the image to be correct in the first place though ;-)
> 
> > I guess one way to solve this would be to really treat 0x10008000 as
> > the default, and relocate the kernel to whatever value make sense on
> > the current platform (even though that needs to be defined).
> > 
> > That way, "fastboot boot zImage" would actually work out of the box,
> > without requiring to set the optional "-b" option to set the kernel
> > base address to some decent value.
> 
> Then I'd say such "default" address should be something like 0xffffffff .

I'd probably agree if we were on a perfect world :)

But the fact is that the tools that are creating these boot.img in
Android all have this default, and *will* fill the kernel address
header to this value.

https://android.googlesource.com/platform/system/core/+/master/fastboot/fastboot.cpp, line 72
https://android.googlesource.com/platform/system/core/+/master/mkbootimg/mkbootimg.c, line 112

So even if we send a patch to Android itself, that won't fix the tools
that are already in the source code of published Android versions, or
the packages bundled in the distribution.

So I think that instead of blindly trusting these tools, U-Boot should
handle that address has the de facto default, even if it doesn't make
any sense :)

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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