[PATCH 00/12] Support to run U-Boot on sc7180 Trogdor Chromebooks

[Stephen Boyd]

Quoting Caleb Connolly (2025-02-20 17:00:30)
> Hi Stephen,
>
> On 2/20/25 20:58, Stephen Boyd wrote:
> > This series supports running U-Boot as a payload on sc7180 Trogdor
> > Chromebooks like Lazor or Wormdingler. This is a jumble of different
> > patches to get to the final goal of booting a Linux distro from the eMMC
> > on Lazor. I've yet to craft a USB stick with a stock distro but I'll
> > probably do that next week.
>
> \o/ wow, this is awesome!

Thanks!

>
> you might have some luck booting pmOS, we build depthcharge compatible
> images for trogdor
>
> https://images.postmarketos.org/bpo/edge/google-trogdor/
>
> There's also a generic ARM64 EFI image that should work. You may need to
> edit the image and remove efi/systemd/drivers/dtbloader.efi from the ESP:
>
> https://images.postmarketos.org/bpo/edge/postmarketos-trailblazer/
>

Cool thanks for the pointers. I'm loading u-boot as a payload from
depthcharge so that I don't have to remove the write protect on the
flash. It's the altfw boot method.

I tried to boot the Debian ISO from a USB stick but it looks like the
FDT memory node isn't modified when I use u-boot to load the DTB from
the one flashed to the eMMC for the ChromeOS installation. Does the
efi_dt_fixup_protocol run in that case? I've never tried any of this
stuff before so I'm learning while I go.

I've been using this sort of flow to read the DTB from the FIT image
that chromeos has:

 bootflow scan -l
 bootflow select 2 # Select the MMC partition for cros bootmethod
 bootflow read
 bootflow info
 fit=$hex_address_for_FDT_from_info_above
 imxtract ${fit} fdt-22 ${fdt_addr_r} # fdt-22 matches my board variant
 fdt addr ${fdt_addr_r}
 load usb 0:2 ${kernel_add_r} /EFI/BOOT/BOOTAA64.EFI
 bootefi ${kernel_addr_r} ${fdt_addr_r}

This seems to work to get me to the installation menu but then when I
run installation the kernel doesn't boot and it looks like memory hasn't
been updated per the earlycon info that I see. I'll continue debugging.

> >
> > The first few patches add support for the particular SoC sc7180 used on
> > Trogdor devices. The next set of patches move the coreboot logic out of
> > x86 into lib to find the coreboot tables on ARM and stash them in global
> > data. Then I have a handful of patches to let the coreboot commands and
> > utilities parse and populate various things like pstore and DT with the
> > proper data from the coreboot tables. Finally, I add the calls to
> > coreboot dram parsing code in the snapdragon board so that if coreboot
> > tables exist we get the memory info from coreboot instead of from an
> > earlier stage DTB.
> >
> > I tested the spi driver with the crosec command. The cros bootflow
> > method almost works, but it seems like chromeos userspace blows up
> > spectacularly likely because crossystem can't figure out what board it
> > is running on. I don't really care too much about booting chromeos
> > userspace here so I'm going to ignore that problem and assume that I can
> > boot some Linux distro because the eMMC can be read by U-Boot and the
> > kernel boots.
>
> Guess it's time I finally get my hands on one of these devices :D
>

I bought a Lazor from eBay for a couple hundred dollars refurbished and
it is basically brand new because the battery was replaced. I want to
get the display working, which I think will require me to port the dsi
and eDP bridge code over even though coreboot would have left everything
largely configured.