[meta-xilinx] Why no support for FSBL?

[Nathan Rossi]

On 21 November 2017 at 07:08, Peter Smith <salerio at gmail.com> wrote:
> Hi, I’m aware of the meta-xilinx-tools layer, but this needs you to have the
> Xilinx SDK installed (unless I’m mistaken), I was wondering ion there were
> any plans to create support in meta-xilinx for building the FSBL without the
> need for the SDK dependency. Peter
>
>
> On 20 Nov 2017, at 21:05, Giordon Stark <kratsg at gmail.com> wrote:
>
> Hi (resending from right address),
>
> You can indeed build the FSBL + boot.bin using the meta-xilinx-tools layer:
> https://github.com/Xilinx/meta-xilinx-tools
>
> Giordon
>
> On Mon, Nov 20, 2017 at 3:03 PM Peter Smith <salerio at gmail.com> wrote:
>>
>> A question, I was wondering why there is no support for building FSBL in a
>> similar way to that provided by meta-xilinx for the PMU firmware, is there a
>> technical reason or is it just one of those things that has not yet been got
>> around to? Thanks in advance Peter.

So it all comes down to bootgen. The boot.bin built by the bootgen
tool from XSDK/etc. has an FSBL specific image table which is how it
encodes multiple images for u-boot.elf, bitstream, etc. Because this
bootgen tool is not available as public code and the special
headers/image table are subject to the whim of the FSBL built (and
indirectly the target version of the Xilinx tools); it is not easy to
provide support for building a complete boot.bin with FSBL outside of
the Xilinx tools.

Building FSBL in the same way as PMU Firmware (as in meta-xilinx) is
possible and years ago I had a very rough recipe for it. However since
U-Boot SPL support appeared (and subsequent support for boot.bin
generation with U-Boot's mkimage) it was much more palatable for Linux
users, as for most cases FSBL was used to load U-Boot anyway and
U-Boot SPL does a better job at that.

Now with meta-xilinx-tools covering FSBL/bootgen I don't see much of a
benefit in having FSBL built how PMU firmware is in meta-xilinx. Since
the reasons behind the users choice to use FSBL are generally because
it is the flow which Xilinx provides, and so it makes more sense to
use the better supported flow of building/configuring it.

Regards,
Nathan