How to introduce RK3288 dts and dtsi
In this issue, the editor will bring you about how to introduce RK3288 dts and dtsi. The article is rich in content and analyzes and narrates it from a professional point of view. I hope you can get something after reading this article.
Device Tree is a data structure that describes hardware, which originates from OpenFirmware (OF). In Linux2.6, too many hardware details of ARM architecture are hard-coded in arch/arm/plat-xxx and arch/arm/mach-xxx. After adopting Device Tree, many hardware details can be passed to Linux directly through it, instead of a lot of redundant coding in kernel.
Device Tree consists of a series of named nodes (node) and attributes (property), and the node itself can contain child nodes. The so-called attributes are actually name and value that appear in pairs.
In Device Tree, descriptive information includes (previously, most of this information was hard-coded into kernel):
Quantity and category of CPU
Memory base address and size
Bus and bridge
Peripheral connection
Interrupt controller and interrupt usage
GPIO controller and GPIO usage
Clock controller and Clock usage
It basically draws a tree on the circuit board (composed of CPU, bus and devices). Bootloader will pass the tree to the kernel, and then the kernel can identify the tree and expand the platform_device, i2c_client, spi_device and other devices in the Linux kernel according to it, and the memory, IRQ and other resources used by these devices are also passed to the kernel, and the kernel will bind these resources to the corresponding devices deployed.
The .dts file is an Device Tree description in ASCII text format. Basically, in ARM Linux, a .dts file corresponds to an ARM machine, which is typically placed in the kernel's arch/arm/boot/dts/ directory. Since a SOC may correspond to multiple machine (a SOC can correspond to multiple products and circuit boards), it is inevitable that these .dts files contain many common parts. In order to simplify, the Linux kernel generally abstracts the common part of SOC or the common part of multiple machine into .dtsi, similar to the header file of C language. The .dts corresponding to the other machine is the .dtsi of include.
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