Porting Cora Z7 Board to barebox

Porting Cora Z7 Board to barebox

[johannes]

I have a Cora Z7 board which I want to port to barebox. The Cora Z7 embeds an
Zynq 7000 SoC with a single core Cortex-A9 and 512 MB DDR3 memory. Barebox
already supports the Zynq 7000 and the Avnet Zedboard.

I have some questions and maybe you can point me in the right direction:

When I am compiling barebox with the zynq_defconfig, as an output I get the file
barebox-avnet-zedboard.img. This file contains the PBL, barebox proper and the
device tree, right?

The Cora Z7 uses a different memory configuration compared to the Zedboard. My
first idea was to use Xilinx FSBL and let the FSBL start barebox. The FSBL can
start an ELF file. But if I use just the compiled barebox file, the device tree
is missing, right? Is there a way to hard code the UART to use for the barebox
console for barebox proper?

The Zynq on the Cora Z7 only embeds a single core Cortex A9 while the SoC on the
Zedboard embeds a dual core Cortex A9. Does this affect the cores initialization
in arch/arm/mach_zynq? 

I am looking forward to your replies. 

Thank you and best regards,
Johannes Roith

Re: Porting Cora Z7 Board to barebox

[Sascha Hauer]

Hi Johannes,

On Mon, Apr 28, 2025 at 07:20:01PM +0200, johannes@gnu-linux.rocks wrote:
> I have a Cora Z7 board which I want to port to barebox. The Cora Z7 embeds an
> Zynq 7000 SoC with a single core Cortex-A9 and 512 MB DDR3 memory. Barebox
> already supports the Zynq 7000 and the Avnet Zedboard.
> 
> I have some questions and maybe you can point me in the right direction:
> 
> When I am compiling barebox with the zynq_defconfig, as an output I get the file
> barebox-avnet-zedboard.img. This file contains the PBL, barebox proper and the
> device tree, right?

Right.

> 
> The Cora Z7 uses a different memory configuration compared to the Zedboard. My
> first idea was to use Xilinx FSBL and let the FSBL start barebox. The FSBL can
> start an ELF file. But if I use just the compiled barebox file, the device tree
> is missing, right?

In case of the Zedboard you could take start_avnet_zedboard.pbl. This
contains all necessary components including device tree and barebox
proper.

However, this binary is linked to 0x0 and the FSBL will likely load it
there. I don't know where the FSBL itself is located.

> Is there a way to hard code the UART to use for the barebox
> console for barebox proper?

Why do you want to hardcode it? Setting the console via device tree is
just fine.

For debugging your early code I recommend CONFIG_DEBUG_LL. For zynq the
UART is hardcoded to ZYNQ_UART1_BASE_ADDR in include/mach/zynq/debug_ll.h.
You can change it in this file.

With CONFIG_DEBUG_LL enabled you can put putc_ll() in your code.

> 
> The Zynq on the Cora Z7 only embeds a single core Cortex A9 while the SoC on the
> Zedboard embeds a dual core Cortex A9. Does this affect the cores initialization
> in arch/arm/mach_zynq?

I don't think so. I haven't used Zynq myself though.

Regards,
  Sascha

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Re: Porting Cora Z7 Board to barebox

[Ahmad Fatoum]

Hi,

On 4/29/25 10:34, Sascha Hauer wrote:
> In case of the Zedboard you could take start_avnet_zedboard.pbl. This
> contains all necessary components including device tree and barebox
> proper.
> 
> However, this binary is linked to 0x0 and the FSBL will likely load it
> there. I don't know where the FSBL itself is located.

The pbl files tend to be a bit bigger, because they are meant only
as input to objcopy. You can add to images/Makefile.zynq, e.g.

  image-$(CONFIG_MACH_ZEDBOARD) += start_avnet_zedboard.elf

And it will generate a much more compact ELF file that should
be interchangeable (I had tested this on ZynqMP).

>> Is there a way to hard code the UART to use for the barebox
>> console for barebox proper?
> 
> Why do you want to hardcode it? Setting the console via device tree is
> just fine.
> 
> For debugging your early code I recommend CONFIG_DEBUG_LL. For zynq the
> UART is hardcoded to ZYNQ_UART1_BASE_ADDR in include/mach/zynq/debug_ll.h.
> You can change it in this file.
> 
> With CONFIG_DEBUG_LL enabled you can put putc_ll() in your code.

CONFIG_DEBUG_PBL is also often useful.

>> The Zynq on the Cora Z7 only embeds a single core Cortex A9 while the SoC on the
>> Zedboard embeds a dual core Cortex A9. Does this affect the cores initialization
>> in arch/arm/mach_zynq?
> 
> I don't think so. I haven't used Zynq myself though.

Cheers,
Ahmad

> 
> Regards,
>   Sascha
> 

-- 
Pengutronix e.K.                  |                             |
Steuerwalder Str. 21              | http://www.pengutronix.de/  |
31137 Hildesheim, Germany         | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686  | Fax:   +49-5121-206917-5555 |