Chris Johns chrisj at rtems.org
Fri Aug 9 23:40:58 UTC 2019

On 10/8/19 2:54 am, Sebastian Huber wrote:
> just my 2ct with respect to the lacking device tree support in the Xilinx Zynq BSP. This is just a historic accident. The BSP was written before we had any device tree support in RTEMS. 

FDT support for the Zynq would be nice however it would need to be more than the
uboot way of handling it, ie loading from a file in RTEMS itself with out uboot.

>In general, I think we should stick to what Linux does on a certain platform.

I am not sure about this. It works for some targets like the BBB and RPi but can
it be universally applied? I see issues.

Xilinx provides the FSBL and you need to make sure this is aligned to your
hardware as it contains the ps7_init code built from the SystemZ designer
interface. For some of the hard IP devices in the Zynq the FDT can work but I am
not sure about the specialised parts like the AXI bus configurations unless it
is exported from the Xilinx tools and complete. Then there is secure mode and
non-bricking issues which the Xilinx FSBL has some support for but I have not
seen in u-boot. All Zynq Linux systems I have seen do not have these things.

> If it boots via a device tree, then the RTEMS BSP should do this as well.

How would you integrate the Xilinx tools to handle this, ie ps7_init and friends?

U-boot provides the FSBL equivalent, MLO or something like that, that is
specific to a build of hardware for example the Microzed. I do not think a
Microzed build will operate on a Picozed as it has 1G of RAM and there is no
support for a Picozed in u-boot master or Xilinx's u-boot fork. I suspect it is
in the Petalinux source tarball. U-boot is GPL and some places ban GPL of all
forms on a target.


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