[U-Boot] [PATCH 2/2] [rfc] support booting arm64 android image

[Daniel Thompson]

On 13/07/17 08:33, Bin Chen wrote:
> Hi Tom,
> 
> Thanks for the review.
> 
> On 13 July 2017 at 04:25, Tom Rini <trini at konsulko.com 
> <mailto:trini at konsulko.com>> wrote:
> 
>     On Tue, Jul 11, 2017 at 03:56:04PM +1000, Bin Chen wrote:
> 
>     > It's my understanding that we are supposed to use booti, instead of bootm,
>     > for arm64 image. But booti lacks of android image support. Bootm has
>     > the andriod image support but lack of the arm64 image handling.
>     >
>     > So, what is suppose the right way of booting an android arm64 image?
>     > or, should we create a separate command?
>     >
>     > This patch is an invitation for that discussion.
>     >
>     > It *hacked* the booti command and it aslo assume the dtb is in the second area
>     > of android boot image. It also has other belives like u-boot should be
>     > in control of where to put the kernnel/ramdisk/dtb images so it ignores
>     > the value specified in the android images.
>     >
>     > Signed-off-by: Bin Chen <bin.chen at linaro.org <mailto:bin.chen at linaro.org>>
> 
>     So, booti is very much for the "Image" format described in the Linux
>     kernel in Documentation/arm64/booting.txt.  One can (and people have)
>     used bootm on aarch64 for "uImage" style kernels and FIT kernels, and I
>     would see being able to boot an aarch64 Android image with bootm as the
>     way to go forward. 
> 
> 
> Are you suggesting that we should use bootm path, instead of booti?
> 
> I have two questions regarding this:
> 
> 1. currently arm64 kernel don't have a uImage kernel target. And I'm not 
> sure
>   if adding that will be something that is wanted and/or sensible.

All arm64 kernels are multi-platform (even if for some minimized builds 
only drivers for one platform are actually enabled). That means a uImage 
kernel target is problematic because the kernel build system does not 
know its eventual physical load address. On arm64 that is entirely 
delegated to the bootloader.

That doesn't mean uImage can never be used; just that the kernel build 
system has no business authoring one.


> 
> 2. bootm path doesn't have the logic that is currently in the booti, 
> such as the
> kernel relocation.
> 
> Also, one other question raised during internal discussion was why the 
> booti
> was created in the first place, if we could have had that implemented in 
> the
> bootm path.
> 
> 
>     The analogy would be that we use bootm for Android
>     on arm not bootz.  Thanks!
> 
>     --
>     Tom
> 
> 
> 
> 
> -- 
> Regards,
> Bin