[U-Boot] [PATCH] qemu-arm: Add persistent environment support

[Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>]

Hi Sumit, Takahiro,

On Wed, 12 Dec 2018 10:42:56 +0900
Takahiro Akashi <takahiro.akashi@linaro.org> wrote:

> On Tue, Dec 11, 2018 at 06:04:05PM +0530, Sumit Garg wrote:
> > On Mon, 26 Nov 2018 at 16:51, Sumit Garg <sumit.garg@linaro.org>
> > wrote:  
> > >
> > > Currently on qemu-arm platforms environment is kept in RAM.
> > > Instead use pflash device 1 to provide persistent environment
> > > support across device reset.
> > >
> > > Also (optionally) provide support for persistent environment
> > > across qemu machine OFF/ON using following instructions:
> > >
> > > - Create envstore.img using qemu-img:
> > >     qemu-img create -f raw envstore.img 64M
> > > - Add a pflash drive parameter to the command line:
> > >     -drive if=pflash,format=raw,index=1,file=envstore.img
> > >
> > > Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
> > > ---
> > >  configs/qemu_arm64_defconfig | 7 +++++++
> > >  configs/qemu_arm_defconfig   | 7 +++++++
> > >  doc/README.qemu-arm          | 6 ++++++
> > >  include/configs/qemu-arm.h   | 8 +++++++-
> > >  4 files changed, 27 insertions(+), 1 deletion(-)
> > >  
> > 
> > Gentle reminder. Please let me know if you have any further
> > comments.  

I'm not too familiar with the UEFI/ATF related aspects here, but I
think that the read-only parts (aka u-boot.bin) and read-write parts
(the U-Boot environment) should belong to different files (which is
what this patch series does). Basically, IMO as a normal user I should
be able to run QEMU on a distro-provided U-Boot binary with something
like:

    qemu-system-arm -bios /usr/share/u-boot/qemu_arm.bin

and not have it fail due to not having write permission to /usr/.

> Another use case is atf + u-boot (although I don't know people are
> interested in it). Put bl1.bin in flash0(0x0-0x4000000) and put
> fip.bin in flash1(0x4000000-0x8000000). Please note that, with
> secure=on, flash0 is in secure and flash1 is in non-secure.
> While I admit that your patch is workable, my point is that there are
> different use cases and it may not be a good idea to put one
> configuration in qemu-arm.h.

Can EDK2 in QEMU boot with ATF and if so, how does it lay out things?
Would it be possible to build U-Boot in such a way that u-boot.bin
could be substituted in existing build scripts or instructions in place
of the EDK2 binary so that things still work the same?

Or in other words, if EDK2 has already has a working
implementation of something (such as the flash layout), IMO we should
prefer to use that instead of reimplementing it in a different
way.

- Tuomas