Re: [PATCH] arm: Add (back) VExpress boards support

[Andre Przywara <andre.przywara@arm.com>]

On Tue, 29 Jun 2021 08:11:22 -0400
Tom Rini <trini@konsulko.com> wrote:

> On Tue, Jun 29, 2021 at 12:45:55PM +0100, Andre Przywara wrote:
> 
> > The v2021.07 merge window saw the removal of the Arm Ltd. Versatile
> > Express platform, along with their CA5, CA9 and TC2 boards. The trigger
> > was the missing conversion of the MMC driver.
> > 
> > Some folks complained about that internally, so bring those boards back,
> > but better than ever:
> > - Use DM and OF_CONTROL for all the boards. Use the .dts files from the
> >   latest Linux kernel (5.13) for that.
> > - Move the board selection choice into the platform's Kconfig.
> > - Clean up some shared config and common definitions.
> > - Drop obsolete features like ATAGs support.
> > - Switch to the DM_ETH version of the SMC911X Ethernet driver.
> > - Drop MMC support.
> > 
> > The PL180 MMC driver actually supports DM_MMC, but that requires a
> > DM_GPIO driver for the card detect GPIO, which we don't have. This
> > specific GPIO is actually handled via the "sysregs" device, so we would
> > need a driver for that. QEMU does not emulate this part, also the DT
> > description is somewhat "special", so this is left for later.
> > 
> > This version compiles without any warning for all three boards now.
> > Tested on QEMU.
> > 
> > Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> > ---
> > Hi,
> > 
> > this relies on the SMC911x driver DT changes, as posted here:
> > https://lists.denx.de/pipermail/u-boot/2021-June/452989.html
> > I put a version with the changes broken down here:
> > https://github.com/Andre-ARM/u-boot/commits/tc2-history
> > 
> > This was tested on QEMU, for vexpress_ca15_tc2_defconfig with:
> > $ qemu-system-arm -M vexpress-a15,secure=on -cpu cortex-a15 -m 1G -smp 1 \
> >   -drive file=tramp-tc2.bin,if=pflash,format=raw,read-only \
> >   -device loader,file=u-boot.bin,addr=0x80800000 -nographic
> > 
> > Where tramp-tc2.bin is a trampoline replacing the board's firmware:
> > 00000000  00 00 a0 e3 80 00 48 e3  10 ff 2f e1
> > (mov r0, #0; movt r0, #0x8080; bx r0)
> > 
> > The vexpress_ca9x4_defconfig uses a different memory map, so the runes are:
> > $ qemu-system-arm -M vexpress-a9 -cpu cortex-a9 -m 1G -smp 1 \
> >   -drive file=tramp-ca9.bin,if=pflash,format=raw,read-only \
> >   -device loader,file=u-boot.bin,addr=0x60800000 -nographic
> > 
> > tramp-ca9.bin:
> > 00000000  00 00 a0 e3 80 00 46 e3  10 ff 2f e1
> > (mov r0, #0; movt r0, #0x6080; bx r0)  
> 
> My big question is how do we run this in CI?  Or does it not _need_ that
> firmware file to really exist?  Or is there a pending change to
> https://gitlab.denx.de/u-boot/u-boot-test-hooks.git to generate / just
> have exist those magic empty bins?  Thanks!

So from digging into this I see that this loads U-Boot's ELF build, via
QEMU's -kernel parameter. Which is fine, but not really what is
happening on real hardware.
I checked and the v2021.04 version worked with this approach, but my
build does not.
I will have a look into this now.

Thanks!
Andre