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

[Tom Rini]

On Sun, Jul 23, 2017 at 11:48:53PM +1000, Bin Chen wrote:
> On 19 July 2017 at 12:53, Tom Rini <trini at konsulko.com> wrote:
> 
> > On Wed, Jul 19, 2017 at 12:44:48PM +1000, Bin Chen wrote:
> > > On 18 July 2017 at 22:32, Tom Rini <trini at konsulko.com> wrote:
> > >
> > > > On Thu, Jul 13, 2017 at 05:33:08PM +1000, Bin Chen wrote:
> > > > > Hi Tom,
> > > > >
> > > > > Thanks for the review.
> > > > >
> > > > > On 13 July 2017 at 04:25, Tom Rini <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>
> > > > > >
> > > > > > 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.
> > > >
> > > > There's some confusion here.  bootm is not only for "uImage" kernels.
> > > > It for example handles the aarch32 Android image format.
> > > >
> > > > > 2. bootm path doesn't have the logic that is currently in the booti,
> > such
> > > > > as the
> > > > > kernel relocation.
> > > >
> > > > Now I'm confused, what is different in an "Android" image for aarch64
> > > > than from a standard aarch64 Linux kernel 'Image' ?
> > > >
> > >
> > > Android image wraps the 'Image'. There is a section called “kernel” in
> > > Android
> > > image, and will place the Image there [1]. Do you think it is the right
> > way
> > > to do that?
> > >
> > > I think that's the case for aarch32 android image as well, but replace
> > the
> > > 'Image' with
> > > aarch32 kernel build target - I don't know what the format of that target
> > > is.
> > >
> > > [1]
> > > https://android.googlesource.com/platform/system/core/+/
> > master/mkbootimg/bootimg.h
> > >
> > >
> > > > > 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.
> > > >
> > > > Well, there's some discussion in the archives about this.  The short
> > > > answer is that "bootm" wasn't supposed to become a "figure out whatever
> > > > this image is, boot it" command.
> > > >
> > >
> > > Good to know the idea beyond that and what bootm isn't supposed to be.
> > > That helps to decide whether we should stuff things into bootm or having
> > a
> > > separate one.
> > >
> > >
> > > > In hindsight, now, I'm thinking that the aarch32 Android image support
> > > > maybe should have gone into "bootandroid" and in turn it would be
> > easier
> > > > to get someone to write a new command, say "bootauto" that would ask
> > > > bootm/bootelf/bootefi/bootandroid/bootz/booti/etc if it liked the
> > image
> > > > found at $address and if so, boot it, and if not, move on to checking
> > > > the next type.
> > > >
> > >
> > > That seems the idea what many people agree upon. Not sure how easy
> > > to move aarch32 support out and I don't have a aarch32 platform to test.
> > > Do you think we'll want to start with aarch64 (considering that may be
> > the
> > > aarch
> > > for most android phone out there) and have a separate boota(ndroid)
> > command?
> >
> > I think the best path forward today is to make sure that whatever
> > aarch64-Image support code that's needed from cmd/booti.c is available
> >
> 
> Just to confirm you are suggesting to move the aarch64-Image support code(*)
> from cmd/booti.c to common/bootm.c, is that right? This sounds good to me.

Well, I think we need to change how cmd/booti.c handles the logic to be
more like how cmd/bootz.c does.  Perhaps arch/arm/lib/image.c.

-- 
Tom
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