[U-Boot] [PATCH] cros: Expand the Chromium OS documentation

[Tristan Bastian]

Hi Simon,


Simon Glass – Fri, 8. February 2019 5:12
> Hi Tristan,
> 
> On Mon, 4 Feb 2019 at 08:01, Tristan Bastian <tristan-c.bastian at gmx.de> wrote:
> >
> > Hi Simon,
> >
> > I'm using the nyan-big chromebook (tegra124).
> > Is it possible to replace coreboot + depthcharge with just u-boot on the
> internal spi flash?
> > If so, do you have some instructions for that?
> 
> Possibly, although I would suggest being careful about that. Make sure
> you have a tool to revert the flash contents. Note that you will not
> have signed firmware so won't get updates. Presumably you are in dev
> mode anyway,

I've already got myself a SOIC flash clip and was able to extract the current content of the spi flash.
 
> The instructions are just to flash the image.bin file that comes out
> of the build, once it exists. But there is no chromeos_nyan target as
> yet. So your only option right now is to build an image without
> verified boot, and use a script to boot Chrome OS. I have not tried on
> this nyan.

I'm not sure to which file you are referring to, since there is no image.bin file..
If I build u-boot with this command: "make -j4 O=b/nyan-big nyan-big_defconfig all"
I'm getting these dot bin files:
-rw-r--r-- 1 tristan tristan 691K Feb  8 08:09 u-boot.bin
-rw-r--r-- 1 tristan tristan 691K Feb  8 08:09 u-boot-dtb.bin
-rw-r--r-- 1 tristan tristan  16M Feb  8 08:09 u-boot-dtb-tegra.bin
-rwxr-xr-x 1 tristan tristan 639K Feb  8 08:09 u-boot-nodtb.bin
-rw-r--r-- 1 tristan tristan  16M Feb  8 08:09 u-boot-nodtb-tegra.bin
-rw-r--r-- 1 tristan tristan  16M Feb  8 08:09 u-boot-tegra.bin

I would only be able to flash one of these files with flashrom to the spi chip if the file size equals the flash size..
I thought the 16MB files would be right, but nyan-big only has a flash size of about 4M..

The spi flash size seems to be configured in "include/configs/nyan-big.h" with:
#define CONFIG_SPI_FLASH_SIZE (4 << 20)
Which is the correct flash size (4194304)..

So should u-boot output a binary that I'm able to flash directly to the spi chip or are there some additional steps needed?
If so, could you give me some hints on what to do?

> > At the moment I'm chainloading u-boot, but this is causing some issues with
> not working LPAE so I'm only getting 2 of my 4GB of memory..
> > So I would like to try and run u-boot natively to see if chainloading is the
> problem or u-boot itself..
> > Or maybe you have some instructions to run coreboot + u-boot without
> depthcharge?
> 
> I suppose you could put U-Boot in the image in instead of dc and it might
> work.
Sorry for asking, but do you have some instructions for replacing dc?

Thanks,
Tristan