[Ground-station] can't find dt-bindings - embedded build for zcu102+ADRV9002 progress and current roadblock

[Michelle Thompson]

Greetings all!

We can produce an SD card image for the zcu102 (our FPGA development
station in Remote Labs that serves Neptune, etc,) in several ways.

1) We have a working Analog Devices Kuiper build.
2) We know how to make a petalinux build (haven't produced one yet, but
would follow the same process as we did for the zcu706+ADRV9371).
3) We are trying to produce a mathworks buildroot build so we can use HDL
Coder (MATLAB/Simulink).

Getting to the point where a zcu102 SD image was produced required
installing some missing packages on Chococat and applying some patches. One
patch we found on the internet and the other we created from the commit
number. We had to add in a symbolic link so that /opt/Xilinx could be found
(for the Vivado SDK) because we have our tools in /tools/Xilinx at Remote
Labs.

We're at the point where we are trying to compile the device tree for the
zcu102-adrv9002. In other words, we want to add the SDR device tree to the
embedded linux image in order to be able to connect to the radio with IIO
from MATLAB and use HDL Coder with minimum friction.

We have the .dts (Device Tree Source) file from Analog Devices github for
the ADRV9002. This file includes several other .dts files. We copied all of
those to the dts directory successfully.

We exported a new psu_init_gpl.c and psu_init_gpl.h from Vivado, using the
reference design from Analog Devices of the zcu102-adrv9002 combination, as
laid out in the "handoff files" part of the directions here:
https://www.mathworks.com/help/hdlcoder/ug/xilinx-zynq-linux-image-for-custom-boards.html

The instructions in the link above are for adding a completely new custom
FPGA dev board to buildroot, and not for the (easier? maybe?) case of
adding a supported radio card to a supported dev board.

Adding a radio card to a supported dev board is what we're trying to do.

I am hoping the workflow of adding a new development board and adding a
supported radio card to a supported development board is the same or
similar process.

If you are reading this and can help, please speak up.I have not found a
walkthrough or explanation or video on this yet. When we get it to work,
we'll write one up.

The exported .c and .h files were different from the ones that were already
there in buildroot in /boards/zcu102/boot/handoff, and this isn't
surprising. The ones already there only know about the zcu102. The new ones
are from the export of the reference design that has both the zcu102 and
the adrv9002 designs in it.

We think that to include a new .dts file, we need to add values - shown
below - to the defconfig file at this level. Note that the zcu102 defconfig
does have a copy and paste typo in the comment header - it says ZC706
(which is a different board), but the commands in the file before we added
ours were correct. They all (correctly) referred to the zcu102. The top two
commands were in the file when we found it. The bottom three commands are
what we added.

The file below is definitely defconfig from
~/neptune/buildroot/board/mathworks/zynqmp/boards/zcu102/defconfig.

###########################################
# ZC706 Options
###########################################
BR2_TARGET_UBOOT_BOARD_DEFCONFIG="xilinx_zynqmp_zcu102_rev1_0"
BR2_PACKAGE_XILINX_BOOTLOADER_UBOOT_TARGET_DIR="board/xilinx/zynqmp/zynqmp-zcu102-rev1.0"

BR2_LINUX_KERNEL_DTS_SUPPORT=y
BR2_LINUX_KERNEL_USE_CUSTOM_DTS=y
BR2_LINUX_KERNEL_CUSTOM_DTS_PATH="/home/abraxas3d/neptune/buildro....
(multiple .dts files)

This moved things forward quite a bit!

But the build script errors out with a failure to find dt-bindings.

Failing to find dt-bindings can be solved with a symbolic link, according
to a couple of posts here and there from people having similar problems
with trying to add custom .dts files to an existing device tree setup in a
linux build, but I do not know where it was looking for dt-bindings in the
first place, or where the "right" dt-bindings include files are. I'm not
sure what to link to what.

Here is the error message snippet and the build log attached:

In file included from arch/arm64/boot/dts/zynqmp-zcu102-revA.dts:12:0,
         from arch/arm64/boot/dts/zynqmp-zcu102-revB.dts:10,
         from arch/arm64/boot/dts/zynqmp-zcu102-rev1.0.dts:10,
         from arch/arm64/boot/dts/zynqmp-zcu102-rev10-adrv9002.dts:10:
arch/arm64/boot/dts/zynqmp.dtsi:15:47: fatal error:
dt-bindings/dma/xlnx-zynqmp-dpdma.h: No such file or directory
 #include <dt-bindings/dma/xlnx-zynqmp-dpdma.h>
                        ^
compilation terminated.
scripts/Makefile.lib:313: recipe for target
'arch/arm64/boot/dts/zynqmp-zcu102-rev10-adrv9002.dtb' failed
make[3]: *** [arch/arm64/boot/dts/zynqmp-zcu102-rev10-adrv9002.dtb] Error 1
arch/arm64/Makefile:114: recipe for target
'zynqmp-zcu102-rev10-adrv9002.dtb' failed
make[2]: *** [zynqmp-zcu102-rev10-adrv9002.dtb] Error 2
package/pkg-generic.mk:227: recipe for target
'/home/abraxas3d/neptune/buildroot/output/zcu102_linux_linaro/build/linux-mathworks_zynq_R21.2.0/.stamp_built'
failed

We can look at the .dtb file produced by mathworks buildroot (before trying
to add the ADRV9002 device files) with fdtdump and see all sorts of things
that we expect - just no radio devices yet.

Optimistic that it's close to working. If you can take a look at this build
on Chococat and explain where the symbolic link needs to go, that would be
a big help.

Thanks everyone! We're also setting things up in Simulink for golden tests
and some doppler experiments, so you should see some initial waveforms and
test results shortly.

If you want to join the team or just observe the engineering firsthand,
please find #Neptune channel on our Slack.

-Michelle Thompson
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