Re: MPC5200b MMC over SPI into PSC6

["Grant Likely" <grant.likely@secretlab.ca>]

On Thu, May 8, 2008 at 9:10 AM, Fabio Tosetto <tosettofabio83@libero.it> wrote:
> Ok, maybe it's better to start from the beginning.
>  Now I'm using a Lite5200b board, just to avoid problems with my hardware,
> and I'm trying to have a bootable kernel.
>
>  With kernel version 2.6.24.6 I do the following commands
>
>  $ make ARCH=powerpc lite5200_defconfig
>  $ make ARCH=powerpc CROSS_COMPILE=powerpc-linux-gnu- uImage
>
>  then I copy the arch/powerpc/boot/uImage and a rootfs.uimage on the board,
> but uBoot stops at the beginning:

Right; some concepts need to be explained now...  There is a major
difference between arch/ppc and arch/powerpc.  In arch/ppc, the kernel
is hard coded with the list of devices in the system.  In
arch/powerpc, the list of devices is captured in a data structure
called the Flattened Device Tree (FDT).  fdt data structures are
generated from the .dts (device tree source) files in
arch/powerpc/boot/dts/.

When you build a uImage with arch/ppc, you get a hard coded kernel
that works with u-boot:  "bootm <kernel_addr> <ramdisk_addr>"

When you build a uImage with arch/powerpc, you get a dynamic kernel
that needs to be passed the device tree blob on boot.  Newer u-boot
supports dts booting: "bootm <kernel_addr> <ramdisk_addr> <dt_addr>"
or "bootm <kernel_addr> - <dt_addr>" if you're not using a ramdisk.

However, if you've got an older u-boot version installed on your
board, you need to create an image that binds the device tree into the
kernel image.  This is called a "cuImage".  So, instead of doing "make
ARCH=powerpc uImage", you should do "make ARCH=powerpc
cuImage.<boardname>".  This 'wraps' the kernel with a boot wrapper
that includes the device tree blob but maintains compatibility with
the old style uImage format.

For example, use "make ARCH=powerpc cuImage.lite5200b" to build an
image for the lite5200b board.  The build scripts will use the
lite5200b.dts file in the dts directory for building the image.  If
you add "fabios-fantastic-board.dts" to arch/powerpc/boot/dts, then
you can build "cuImage.fabios-fantastic-board".  :-)

>  The only way I was able to get something working, even though it sounds a
> little strange to me, is loading the config from powerpc folder but
> compiling in ppc
>
>  $ make ARCH=powerpc lite5200_defconfig
>  $ make ARCH=ppc CROSS_COMPILE=powerpc-linux-gnu- uImage

ARCH=ppc and ARCH=powerpc are completely different beasts.  Forget
that you even know about ARCH=ppc for this entire exercise.

Cheers,
g.

-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.