topic Re: What is the most up-to-date reference for understanding the device tree binary and how it is built? in i.MX Processors

What is the most up-to-date reference for understanding the device tree binary and how it is built?

EdSutter — Mon, 11 Nov 2013 20:24:03 GMT

I'm running with SABRESDB in preparation for my custom hardware.

My custom hardware core is similar to SABRESDB; but I still wanna make sure I know how to build/modify the .dtb file.

I'm currently reading through the kernel's Documentation/devicetree/usage-mode.txt and also http://devicetree.org/Device_Tree_Usage,

are these documentation sources the correct place to be reading up on the FDT stuff used with iMX6/SabreSDB or is there

additional/other places to get better acquainted with this?

Thanks in advance,

EDIT---

Perhaps a more fundamental question is: will I need to modify the .dts file for custom iMX6 hardware or is this file something that describes the SOC/CPU and its IO independent of the circuitry around the SOC?

Re: What is the most up-to-date reference for understanding the device tree binary and how it is built?

fabio_estevam — Mon, 11 Nov 2013 22:15:54 GMT

Ed,

A .dts file describes a particular board. You can start with imx6qdl-sabresd.dtsi, for example and adapt it to your own board.

You can see how other mx6 boards are supported in device tree: ls -al arch/arm/boot/dts/imx6*

Regards,

Fabio Estevam

Re: What is the most up-to-date reference for understanding the device tree binary and how it is built?

EdSutter — Mon, 11 Nov 2013 22:48:14 GMT

Fabio,

Ok, I've been looking at this since I posted the question. I see the .dts file is processed by 'dtc' (device-tree-compiler i assume?)

to generate the .dtb file. Does this binary translate into runtime initialization in the kernel somewhere?

One other question...

I noticed an option in kernel menuconfig: "Use appended device tree blob to zImage (EXPERIMENTAL)".

Does this do what it implies; thus eliminating the need to download the separate .dtb file and using the 3-argument bootm command?

Thanks much,

Re: What is the most up-to-date reference for understanding the device tree binary and how it is built?

fabio_estevam — Wed, 13 Nov 2013 00:35:14 GMT

Hi Ed,

Yes, when you run "make imx6q-sabresd.dtb' , the dts file is converted to the dtb binary.

Just replied in more details about the appended device tree in another thread.

Regards,

Fabio Estevam