[U-Boot] Support of device-tree for PowerPC platform: Query

[Bin Meng]

Hi Prabhakar,

On Mon, Jul 2, 2018 at 11:27 PM, Prabhakar Kushwaha
<prabhakar.kushwaha at nxp.com> wrote:
> Dear Bin,
>
> Coming back to x86 example.
>
>> -----Original Message-----
>> From: Bin Meng [mailto:bmeng.cn at gmail.com]
>> Sent: Friday, June 29, 2018 7:03 AM
>> To: York Sun <york.sun at nxp.com>
>> Cc: Simon Glass <sjg at chromium.org>; Prabhakar Kushwaha
>> <prabhakar.kushwaha at nxp.com>; u-boot at lists.denx.de
>> Subject: Re: [U-Boot] Support of device-tree for PowerPC platform: Query
>>
>> Hi York,
>>
>> On Thu, Jun 28, 2018 at 11:32 PM, York Sun <york.sun at nxp.com> wrote:
>> > On 06/27/2018 10:53 PM, Bin Meng wrote:
>> > <snip>
>> >>
>> >>> Can the DT perhaps go before U-Boot in the flash? We would need a
>> >>> way to find it though.
>> >>>
>> >>
>> >> I don't see any issue that DT go after U-Boot in the flash. x86 does
>> >> this way, and its reset vector is also the last address of flash.
>> >>
>> >
>> > Big issue. e500 runs from the last address of the flash. We cannot put
>> > DT after U-Boot.
>>
>> Looks you did not get it. I know e500 reset vector is the last 4 bytes below 4G.
>> This is similar to x86. DTB can be put after the u-boot image without reset
>> vector. You may check how x86 does this.
>>
>
> I tried to search thing for x86 but did not succeed ☹
>

You can test x86 build easily with QEMU.

$ make qemu-x86_defconfig
$ make V=1

This way you can see how u-boot.rom image is built.

> I request you to help me with sample code and boot flow.
> I will try to understand and see how it can help PowerPC.
>

Please see the sample build flow below:

1.  objcopy --gap-fill=0xff  -O binary -R .start16 -R .resetvec u-boot
u-boot-nodtb.bin

.start16 and .resetvec is the x86 boot vector. This is similar to PPC
BookE's reset vector. These two sections are removed to generate a new
u-boot-nodtb binary.

2. cat arch/x86/dts/qemu-x86_i440fx.dtb > dts/dt.dtb
    cat u-boot-nodtb.bin dts/dt.dtb > u-boot-dtb.bin

Append dtb to the end of the u-boot-nodtb binary and get a new
u-boot-dtb binary.

3. cp dts/dt.dtb u-boot.dtb
    objcopy --gap-fill=0xff  -O binary -j .start16 -j .resetvec u-boot
u-boot-x86-16bit.bin

Create a binary which contains the reset vector.

4. ./tools/binman/binman -d u-boot.dtb -O . -I . -I
./board/emulation/qemu-x86 u-boot-x86-16bit.bin

Use binman to assemble the final u-boot.rom image.

Regards,
Bin