Sebastian Huber sebastian.huber at embedded-brains.de
Mon Aug 12 05:13:32 UTC 2019

On 10/08/2019 01:40, Chris Johns wrote:
> 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.

Yes, but U-Boot is not the only boot loader providing a device tree. 
There is no strong connection between U-Boot and a device tree, these 
are independent concepts.

>> 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.

I don't know the Xilinx Zynq good enough. How do yo get the device 
capabilities and memory map if you don't have a device tree? The device 
tree is an open format for this purpose.

Sebastian Huber, embedded brains GmbH

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