前言
前几月学了设备树，期间一直听说有绑定文档这个东西，但是一直没看，最近有时间学习了一下如何阅读绑定文档。
示例文档的来源
本篇文章对照着下面这篇文章进行解读。来源为 nxp-imx/linux-imx:if-6.12-y 仓库的 Documentation/devicetree/bindings/net/can/fsl,flexcan.yaml。此文档描述了 FlexCAN(CAN控制器外设) 节点下的相关属性信息。
# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
%YAML 1.2
---
$id: http://devicetree.org/schemas/net/can/fsl,flexcan.yaml#
$schema: http://devicetree.org/meta-schemas/core.yaml#
title:
Flexcan CAN controller on Freescale's ARM and PowerPC system-on-a-chip (SOC).
maintainers:
- Marc Kleine-Budde <mkl@pengutronix.de>
allOf:
- $ref: can-controller.yaml#
properties:
compatible:
oneOf:
- enum:
- fsl,imx95-flexcan
- fsl,imx93-flexcan
- fsl,imx8qm-flexcan
- fsl,imx8mp-flexcan
- fsl,imx6q-flexcan
- fsl,imx28-flexcan
- fsl,imx25-flexcan
- fsl,p1010-flexcan
- fsl,vf610-flexcan
- fsl,ls1021ar2-flexcan
- fsl,lx2160ar1-flexcan
- items:
- enum:
- fsl,imx53-flexcan
- fsl,imx35-flexcan
- const: fsl,imx25-flexcan
- items:
- enum:
- fsl,imx7d-flexcan
- fsl,imx6ul-flexcan
- fsl,imx6sx-flexcan
- const: fsl,imx6q-flexcan
- items:
- enum:
- fsl,ls1028ar1-flexcan
- const: fsl,lx2160ar1-flexcan
reg:
maxItems: 1
interrupts:
maxItems: 1
clocks:
maxItems: 2
clock-names:
items:
- const: ipg
- const: per
clock-frequency:
description: |
The oscillator frequency driving the flexcan device, filled in by the
boot loader. This property should only be used the used operating system
doesn't support the clocks and clock-names property.
power-domains:
maxItems: 1
xceiver-supply:
description: Regulator that powers the CAN transceiver.
big-endian:
$ref: /schemas/types.yaml#/definitions/flag
description: |
This means the registers of FlexCAN controller are big endian. This is
optional property.i.e. if this property is not present in device tree
node then controller is assumed to be little endian. If this property is
present then controller is assumed to be big endian.
can-transceiver:
$ref: can-transceiver.yaml#
unevaluatedProperties: false
fsl,stop-mode:
description: |
Register bits of stop mode control.
The format should be as follows:
<gpr req_gpr req_bit>
gpr is the phandle to general purpose register node.
req_gpr is the gpr register offset of CAN stop request.
req_bit is the bit offset of CAN stop request.
$ref: /schemas/types.yaml#/definitions/phandle-array
items:
- items:
- description: The 'gpr' is the phandle to general purpose register node.
- description: The 'req_gpr' is the gpr register offset of CAN stop request.
maximum: 0xff
- description: The 'req_bit' is the bit offset of CAN stop request.
maximum: 0x1f
fsl,clk-source:
description: |
Select the clock source to the CAN Protocol Engine (PE). It's SoC
implementation dependent. Refer to RM for detailed definition. If this
property is not set in device tree node then driver selects clock source 1
by default.
0: clock source 0 (oscillator clock)
1: clock source 1 (peripheral clock)
$ref: /schemas/types.yaml#/definitions/uint8
default: 1
minimum: 0
maximum: 1
wakeup-source:
$ref: /schemas/types.yaml#/definitions/flag
description:
Enable CAN remote wakeup.
fsl,scu-index:
description: |
The scu index of CAN instance.
For SoCs with SCU support, need setup stop mode via SCU firmware, so this
property can help indicate a resource. It supports up to 3 CAN instances
now.
$ref: /schemas/types.yaml#/definitions/uint8
minimum: 0
maximum: 2
termination-gpios: true
termination-ohms: true
required:
- compatible
- reg
- interrupts
additionalProperties: false
examples:
- |
can@1c000 {
compatible = "fsl,p1010-flexcan";
reg = <0x1c000 0x1000>;
interrupts = <48 0x2>;
interrupt-parent = <&mpic>;
clock-frequency = <200000000>;
fsl,clk-source = /bits/ 8 <0>;
};
- |
#include <dt-bindings/interrupt-controller/irq.h>
can@2090000 {
compatible = "fsl,imx6q-flexcan";
reg = <0x02090000 0x4000>;
interrupts = <0 110 IRQ_TYPE_LEVEL_HIGH>;
clocks = <&clks 1>, <&clks 2>;
clock-names = "ipg", "per";
fsl,stop-mode = <&gpr 0x34 28>;
fsl,scu-index = /bits/ 8 <1>;
};
- |
#include <dt-bindings/interrupt-controller/irq.h>
#include <dt-bindings/gpio/gpio.h>
can@2090000 {
compatible = "fsl,imx6q-flexcan";
reg = <0x02090000 0x4000>;
interrupts = <0 110 IRQ_TYPE_LEVEL_HIGH>;
clocks = <&clks 1>, <&clks 2>;
clock-names = "ipg", "per";
fsl,stop-mode = <&gpr 0x34 28>;
termination-gpios = <&gpio1 0 GPIO_ACTIVE_LOW>;
termination-ohms = <120>;
};