Fastest way to generate device-tree

[nlbutts]

I find myself fighting with the device-tree. What is the fastest way to generate the device tree? 

I've tried:

petalinux-build -b device-tree

This takes about a minute on my computer. I've also tried:

petalinux-build -c device-tree -x build

But that seems to take about the same amount of time.

I found this post on Stackoverflow: https://stackoverflow.com/questions/38917745/quick-rebuild-of-device-tree-only-with-yocto-bitbake

The dtc aproach doesn't work, it appears I need to pre-process the device tree files into a single file (using GCC???). 

[rfs613]

Not sure if this will help you, but... if the .dts and .dtsi files located within the kernel source tree, then you can use the kernel's main Makefile to rebuild the .dtb.  For example for arch/arm/boot/dts/zynq-zc702.dts you would run:

make ARCH=arm zynq-zc702.dtb

The above is done in the source code of the kernel (or wherever it was built). It will run gcc to combine multiple files, and then runs dtc to generate the .dtb. Takes less than 1 second on my machine.

[nlbutts]

Thanks for the reply. That doesn't work with Petalinux unfortunately. 

[stephenm]

you can create it manually. See the WIKI below:

https://xilinx-wiki.atlassian.net/wiki/spaces/A/pages/18841722/ZCU102+Image+creation+in+OSL+flow

[nlbutts]

I'm not sure I follow. That page indicates you can use the DTC to compile your DTS to a DTB file:

dtc -I dts -O dtb -o my_dts/system-top.dtb my_dts/system-top.dts

The problem is the DTS/DTSI files that Petalinux generates has non-DTC compliant text in it. For example,t he ZCU104 system-top-dts file looks like this:

/*
 * CAUTION: This file is automatically generated by Xilinx.
 * Version:  
 * Today is: Thu Jan 10 14:31:11 2019
 */


/dts-v1/;
#include "zynqmp.dtsi"
#include "zynqmp-clk-ccf.dtsi"
#include "zcu104-revc.dtsi"
#include "pl.dtsi"
#include "pcw.dtsi"
/ {
	chosen {
		bootargs = "earlycon clk_ignore_unused";
		stdout-path = "serial0:115200n8";
	};
	aliases {
		ethernet0 = &gem3;
		i2c0 = &i2c1;
		i2c1 = &sensor_iic;
		serial0 = &uart0;
		serial1 = &uart1;
		spi0 = &qspi;
	};
	memory {
		device_type = "memory";
		reg = <0x0 0x0 0x0 0x7ff00000>;
	};
};
#include "system-user.dtsi"

Those #includes are not valid syntax. Some program needs to pre-process those includes to pull them in (like a C compiler pre-processor output). Further, my system-user.dtsi file contains includes from C header files:

#include <dt-bindings/media/xilinx-vip.h>
...
xlnx,video-format = <XVIP_VF_MONO_SENSOR>;

This needs to be converted to a number and not a symbolic value. When I run the DTC on the top level DTS file I get the following errors:

nlbutts@ubuntu16:~/projects/maza_linux$ ./build/tmp/work/zcu104_zynqmp-xilinx-linux/device-tree/xilinx+gitAUTOINC+b7466bbeee-r0/recipe-sysroot-native/usr/bin/dtc -I dts -O dtb -o system.dtb -i./components/plnx_workspace/device-tree/device-tree ./components/plnx_workspace/device-tree/device-tree/system-top.dts
Error: ./components/plnx_workspace/device-tree/device-tree/system-top.dts:9.1-9 syntax error
FATAL ERROR: Unable to parse input tree
n

I tried to use GCC -E, but the DTC syntax uses #, which causes problems. 

[rfs613]

You're on the right track... and yes, you can call the "dtc" command directly. But as you also noted, the #includes need to be pre-processed. This is done using the C pre-processor (gcc -E is a way of running just the pre-processor).

Figuring out the exact right options to pass (include paths, etc) can be a bit fiddly. That's why I mentioned using the kernel's existing Makefile, which allows you to just do "make NAME.dtb" and it will do the gcc -E followed by dtc commands for you.

Doing it manually is certainly possible. If the system-top.dts is in the same place as the #includes it relies on, then you can just do the following:

cd my_dts
gcc -E -nostdinc -undef -D__DTS__ -x assembler-with-cpp -o system-top.dts.tmp system-top.dts
dtc -I dts -O dtb -o system-top.dtb system-top.dts.tmp

If the #includes are located in other places, you will need to add one or more -I flags to the gcc command. Each one specifies an additional directory to search for includes.

[stephenm]

@rfs613 nice. Ill update the wiki to include this. However, in the OSL flow, there is no sytem-user.dtsi, but still useful info.

So, for reference:

cd <plnx_proj_dir>\components\plnx_workspace\device-tree\device-tree

gcc -I ../../../../project-spec/meta-user/recipes-bsp/device-tree/files -E -nostdinc -undef -D__DTS__ -x assembler-with-cpp -o system-top.dts.tmp system-top.dts

dtc -I dts -O dtb system-top.dtb system-top.dts.tmp

You can then verify, by converting back:

dtc -I dtb -O dts dump.dts system-top.dts.tmp 

In my case, the only thing in the system-user.dtsi was:

&gem3 {
 local-mac-address = [00 0a 35 00 22 02];
};

So, check if this was applied to the gem node:

  ethernet@ff0e0000 {
   compatible = "cdns,zynqmp-gem\0cdns,gem";
   status = "okay";
   interrupt-parent = <0x04>;
   interrupts = <0x00 0x3f 0x04 0x00 0x3f 0x04>;
   reg = <0x00 0xff0e0000 0x00 0x1000>;
   clock-names = "pclk\0hclk\0tx_clk\0rx_clk\0tsu_clk";
   #address-cells = <0x01>;
   #size-cells = <0x00>;
   #stream-id-cells = <0x01>;
   iommus = <0x09 0x877>;
   power-domains = <0x11>;
   clocks = <0x03 0x1f 0x03 0x34 0x03 0x30 0x03 0x34 0x03 0x2c>;
   phy-handle = <0x12>;
   pinctrl-names = "default";
   pinctrl-0 = <0x13>;
   phy-mode = "rgmii-id";
   xlnx,ptp-enet-clock = <0x00>;
   local-mac-address = [00 0a 35 00 22 02];

   phy@c {
    reg = <0x0c>;
    ti,rx-internal-delay = <0x08>;
    ti,tx-internal-delay = <0x0a>;
    ti,fifo-depth = <0x01>;
    ti,rxctrl-strap-worka;
    phandle = <0x12>;
   };
  };

[gsatish10]

Hi

From Linux kernel directory

"make arch=ARM  CROSS_COMPILE=arm-xilinx-linux-gnueabi-   dtbc" 

this provides .dtb files for corrspending platform boards , which is intiated initailly with defconfig

Ex. For xilinx boards, zc702.dtb, zedboard.dtb etc.. will be created.

you can take whatever the board you want,

because here .dtsi represents SoC , .dts represents board file

when we say make ARCH=arm dtbc, it will create for all boards .dts files

Provide kudos if post is helpful

Thanks & Regards

Satish G   

[stephenm]

https://xilinx-wiki.atlassian.net/wiki/spaces/A/pages/136904764/Creating+Devicetree+from+Devicetree+Generator+for+Zynq+Ultrascale+and+Zynq+7000

[archangel-lightworks]

"I find myself fighting with the device-tree"

I'm still licking my wounds... lol

The best way I know for things computers take more than a minute is to do something else in the meantime.

[stephenm]

any particular issues you want to discuss

[milosoftware]

The issue is inside petalinux.

Plain vanilla OpenEmbedded or Yocto devicetree recipes and "plain" kernel compile flows take about a second to compile a new devicetree.

petalinux does "something" in the do_configure stage that takes about a minute on blazing fast machines, and is limited to only a single CPU core. I don't know what it does there. This "something" is not related to the devicetree  compiler or preprocessor.

So the apparent only way to get faster devicetree compile times is to avoid using petalinux.

[stephenm]

Petalinux is based on Yocto. Yocto will use bitbake to organise what tasks to build your binary. You can set the number of CPU in the local.conf to run these tasks in parallel. 

You can look at the recipe to see what is happening. 

For devicetree for example

Source git and checkout correct branch

Build dts for target proc

Precompile

Compile

Copy to petalinux project

Run mkimage to create image.ub

I have a wiki below that you can use to isolate the DT from petalinux

https://xilinx-wiki.atlassian.net/wiki/spaces/A/pages/341082130/Quick+guide+to+Debugging+Device+Tree+Generator+Issues