设备树简介¶
Device Tree是一种描述硬件的数据结构，
DTS(Device Tree Source)就是用来描述目标板硬件信息的源文件。
设备树基本数据格式¶
device tree是一个简单的节点和属性树，属性是键值对，节点可以包含属性和子节点。下面是一个.dts格式的简单设备树。
/ {
node1 {
a-string-property = "A string";
a-string-list-property = "first string", "second string";
a-byte-data-property = [0x01 0x23 0x34 0x56];
child-node1 {
first-child-property;
second-child-property = <1>;
a-string-property = "Hello, world";
};
child-node2 {
};
};
node2 {
an-empty-property;
a-cell-property = <1 2 3 4>; /* each number (cell) is a uint32 */
child-node1 {
};
};
};
编译设备树后，可以使用
dtc -I dtb -O dts xxx.dtb -o xxx.dts
来查看实际生成的设备树文件
在运行系统时，/sys/firmware/devicetree 可以查看实际使用的是设备树
设备树常用操作¶
删除属性¶
/ {
... ...
demo1: demo1 {
compatible = "demo1";
property1 = <1>;
property2;
property3 = <2>;
property4;
};
};
&demo1 {
/delete-property/property2;
/delete-property/property3;
};
删除节点¶
memory_DDR1@c0000000 {
device_type = "memory";
reg = <0 0xc0000000 0 0x40000000>;
};
/ {
/delete-node/ memory_DDR1@c0000000;
};
设备树实例解析¶
下面解析sun8i-v3s.dtsi设备树实例
#include <dt-bindings/interrupt-controller/arm-gic.h>
#include <dt-bindings/clock/sun8i-v3s-ccu.h>
#include <dt-bindings/reset/sun8i-v3s-ccu.h>
/ {
#address-cells = <1>; //表示子节点默认用一个uint32表示地址（32位系统），如果是64位系统将是2
#size-cells = <1>; //表示子节点默认用一个uint32表示大小
interrupt-parent = <&gic>; //interrupt-parent是独立字段，表示整个设备的中断父节点是gic
//<&gic>表示取gic地址。gic配置详见文件末尾
chosen {
#address-cells = <1>;
#size-cells = <1>;
ranges;
simplefb_lcd: framebuffer@0 {
compatible = "allwinner,simple-framebuffer",
"simple-framebuffer";
allwinner,pipeline = "de0-lcd0";
clocks = <&ccu CLK_BUS_TCON0>, <&display_clocks 0>,
<&display_clocks 6>, <&ccu CLK_TCON0>;
status = "disabled";
};
};
cpus {
#address-cells = <1>;
#size-cells = <0>;
cpu@0 {
compatible = "arm,cortex-a7";
device_type = "cpu";
reg = <0>;
clocks = <&ccu CLK_CPU>;
};
};
de: display-engine {
compatible = "allwinner,sun8i-v3s-display-engine";
allwinner,pipelines = <&mixer0>;
status = "disabled";
};
timer {
compatible = "arm,armv7-timer";
interrupts = <GIC_PPI 13 (GIC_CPU_MASK_SIMPLE(4) | IRQ_TYPE_LEVEL_LOW)>,
<GIC_PPI 14 (GIC_CPU_MASK_SIMPLE(4) | IRQ_TYPE_LEVEL_LOW)>,
<GIC_PPI 11 (GIC_CPU_MASK_SIMPLE(4) | IRQ_TYPE_LEVEL_LOW)>,
<GIC_PPI 10 (GIC_CPU_MASK_SIMPLE(4) | IRQ_TYPE_LEVEL_LOW)>;
};
clocks {
#address-cells = <1>;
#size-cells = <1>;
ranges;
osc24M: osc24M_clk {
#clock-cells = <0>;
compatible = "fixed-clock";
clock-frequency = <24000000>;
clock-output-names = "osc24M";
};
osc32k: osc32k_clk {
#clock-cells = <0>;
compatible = "fixed-clock";
clock-frequency = <32768>;
clock-output-names = "osc32k";
};
};
soc {
compatible = "simple-bus";
#address-cells = <1>;
#size-cells = <1>;
ranges;
display_clocks: clock@1000000 {
compatible = "allwinner,sun8i-v3s-de2-clk";
reg = <0x01000000 0x100000>;
clocks = <&ccu CLK_DE>,
<&ccu CLK_BUS_DE>;
clock-names = "mod",
"bus";
resets = <&ccu RST_BUS_DE>;
#clock-cells = <1>;
#reset-cells = <1>;
};
mixer0: mixer@1100000 {
compatible = "allwinner,sun8i-v3s-de2-mixer";
reg = <0x01100000 0x100000>;
clocks = <&display_clocks 0>,
<&display_clocks 6>;
clock-names = "bus",
"mod";
resets = <&display_clocks 0>;
assigned-clocks = <&display_clocks 6>;
assigned-clock-rates = <150000000>;
ports {
#address-cells = <1>;
#size-cells = <0>;
mixer0_out: port@1 {
#address-cells = <1>;
#size-cells = <0>;
reg = <1>;
mixer0_out_tcon0: endpoint@0 {
reg = <0>;
remote-endpoint = <&tcon0_in_mixer0>;
};
};
};
};
tcon0: lcd-controller@1c0c000 {
compatible = "allwinner,sun8i-v3s-tcon";
reg = <0x01c0c000 0x1000>;
interrupts = <GIC_SPI 86 IRQ_TYPE_LEVEL_HIGH>;
clocks = <&ccu CLK_BUS_TCON0>,
<&ccu CLK_TCON0>;
clock-names = "ahb",
"tcon-ch0";
clock-output-names = "tcon-pixel-clock";
resets = <&ccu RST_BUS_TCON0>;
reset-names = "lcd";
status = "disabled";
ports {
#address-cells = <1>;
#size-cells = <0>;
tcon0_in: port@0 {
#address-cells = <1>;
#size-cells = <0>;
reg = <0>;
tcon0_in_mixer0: endpoint@0 {
reg = <0>;
remote-endpoint = <&mixer0_out_tcon0>;
};
};
tcon0_out: port@1 {
#address-cells = <1>;
#size-cells = <0>;
reg = <1>;
};
};
};
mmc0: mmc@01c0f000 {
compatible = "allwinner,sun7i-a20-mmc";
reg = <0x01c0f000 0x1000>;
clocks = <&ccu CLK_BUS_MMC0>,
<&ccu CLK_MMC0>,
<&ccu CLK_MMC0_OUTPUT>,
<&ccu CLK_MMC0_SAMPLE>;
clock-names = "ahb",
"mmc",
"output",
"sample";
resets = <&ccu RST_BUS_MMC0>;
reset-names = "ahb";
interrupts = <GIC_SPI 60 IRQ_TYPE_LEVEL_HIGH>;
status = "disabled";
#address-cells = <1>;
#size-cells = <0>;
};
mmc1: mmc@01c10000 {
compatible = "allwinner,sun7i-a20-mmc";
reg = <0x01c10000 0x1000>;
clocks = <&ccu CLK_BUS_MMC1>,
<&ccu CLK_MMC1>,
<&ccu CLK_MMC1_OUTPUT>,
<&ccu CLK_MMC1_SAMPLE>;
clock-names = "ahb",
"mmc",
"output",
"sample";
resets = <&ccu RST_BUS_MMC1>;
reset-names = "ahb";
interrupts = <GIC_SPI 61 IRQ_TYPE_LEVEL_HIGH>;
pinctrl-names = "default";
pinctrl-0 = <&mmc1_pins>;
status = "disabled";
#address-cells = <1>;
#size-cells = <0>;
};
mmc2: mmc@01c11000 {
compatible = "allwinner,sun7i-a20-mmc";
reg = <0x01c11000 0x1000>;
clocks = <&ccu CLK_BUS_MMC2>,
<&ccu CLK_MMC2>,
<&ccu CLK_MMC2_OUTPUT>,
<&ccu CLK_MMC2_SAMPLE>;
clock-names = "ahb",
"mmc",
"output",
"sample";
resets = <&ccu RST_BUS_MMC2>;
reset-names = "ahb";
interrupts = <GIC_SPI 62 IRQ_TYPE_LEVEL_HIGH>;
status = "disabled";
#address-cells = <1>;
#size-cells = <0>;
};
usb_otg: usb@01c19000 {
compatible = "allwinner,sun8i-h3-musb";
reg = <0x01c19000 0x0400>;
clocks = <&ccu CLK_BUS_OTG>;
resets = <&ccu RST_BUS_OTG>;
interrupts = <GIC_SPI 71 IRQ_TYPE_LEVEL_HIGH>;
interrupt-names = "mc";
phys = <&usbphy 0>;
phy-names = "usb";
extcon = <&usbphy 0>;
status = "disabled";
};
usbphy: phy@01c19400 {
compatible = "allwinner,sun8i-v3s-usb-phy";
reg = <0x01c19400 0x2c>,
<0x01c1a800 0x4>;
reg-names = "phy_ctrl",
"pmu0";
clocks = <&ccu CLK_USB_PHY0>;
clock-names = "usb0_phy";
resets = <&ccu RST_USB_PHY0>;
reset-names = "usb0_reset";
status = "disabled";
#phy-cells = <1>;
};
ehci0: usb@01c1a000 {
compatible = "allwinner,sun8i-v3s-ehci", "generic-ehci";
reg = <0x01c1a000 0x100>;
interrupts = <GIC_SPI 72 IRQ_TYPE_LEVEL_HIGH>;
clocks = <&ccu CLK_BUS_EHCI0>, <&ccu CLK_BUS_OHCI0>;
resets = <&ccu RST_BUS_EHCI0>, <&ccu RST_BUS_OHCI0>;
status = "disabled";
};
ohci0: usb@01c1a400 {
compatible = "allwinner,sun8i-v3s-ohci", "generic-ohci";
reg = <0x01c1a400 0x100>;
interrupts = <GIC_SPI 73 IRQ_TYPE_LEVEL_HIGH>;
clocks = <&ccu CLK_BUS_EHCI0>, <&ccu CLK_BUS_OHCI0>,
<&ccu CLK_USB_OHCI0>;
resets = <&ccu RST_BUS_EHCI0>, <&ccu RST_BUS_OHCI0>;
status = "disabled";
};
ccu: clock@01c20000 {
compatible = "allwinner,sun8i-v3s-ccu";
reg = <0x01c20000 0x400>;
clocks = <&osc24M>, <&osc32k>;
clock-names = "hosc", "losc";
#clock-cells = <1>;
#reset-cells = <1>;
};
rtc: rtc@01c20400 {
compatible = "allwinner,sun6i-a31-rtc";
reg = <0x01c20400 0x54>;
interrupts = <GIC_SPI 40 IRQ_TYPE_LEVEL_HIGH>,
<GIC_SPI 41 IRQ_TYPE_LEVEL_HIGH>;
};
pio: pinctrl@01c20800 {
compatible = "allwinner,sun8i-v3s-pinctrl";
reg = <0x01c20800 0x400>;
interrupts = <GIC_SPI 15 IRQ_TYPE_LEVEL_HIGH>,
<GIC_SPI 17 IRQ_TYPE_LEVEL_HIGH>;
clocks = <&ccu CLK_BUS_PIO>, <&osc24M>, <&osc32k>;
clock-names = "apb", "hosc", "losc";
gpio-controller;
#gpio-cells = <3>;
interrupt-controller;
#interrupt-cells = <3>;
i2c0_pins: i2c0 {
pins = "PB6", "PB7";
function = "i2c0";
};
uart0_pins_a: uart0@0 {
pins = "PB8", "PB9";
function = "uart0";
};
mmc0_pins_a: mmc0@0 {
pins = "PF0", "PF1", "PF2", "PF3",
"PF4", "PF5";
function = "mmc0";
drive-strength = <30>;
bias-pull-up;
};
mmc1_pins: mmc1 {
pins = "PG0", "PG1", "PG2", "PG3",
"PG4", "PG5";
function = "mmc1";
drive-strength = <30>;
bias-pull-up;
};
spi0_pins: spi0 {
pins = "PC0", "PC1", "PC2", "PC3";
function = "spi0";
};
};
timer@01c20c00 {
compatible = "allwinner,sun4i-a10-timer";
reg = <0x01c20c00 0xa0>;
interrupts = <GIC_SPI 18 IRQ_TYPE_LEVEL_HIGH>,
<GIC_SPI 19 IRQ_TYPE_LEVEL_HIGH>;
clocks = <&osc24M>;
};
wdt0: watchdog@01c20ca0 {
compatible = "allwinner,sun6i-a31-wdt";
reg = <0x01c20ca0 0x20>;
interrupts = <GIC_SPI 25 IRQ_TYPE_LEVEL_HIGH>;
};
lradc: lradc@1c22800 {
compatible = "allwinner,sun4i-a10-lradc-keys";
reg = <0x01c22800 0x400>;
interrupts = <GIC_SPI 30 IRQ_TYPE_LEVEL_HIGH>;
status = "disabled";
};
uart0: serial@01c28000 {
compatible = "snps,dw-apb-uart";
reg = <0x01c28000 0x400>;
interrupts = <GIC_SPI 0 IRQ_TYPE_LEVEL_HIGH>;
reg-shift = <2>;
reg-io-width = <4>;
clocks = <&ccu CLK_BUS_UART0>;
resets = <&ccu RST_BUS_UART0>;
status = "disabled";
};
uart1: serial@01c28400 {
compatible = "snps,dw-apb-uart";
reg = <0x01c28400 0x400>;
interrupts = <GIC_SPI 1 IRQ_TYPE_LEVEL_HIGH>;
reg-shift = <2>;
reg-io-width = <4>;
clocks = <&ccu CLK_BUS_UART1>;
resets = <&ccu RST_BUS_UART1>;
status = "disabled";
};
uart2: serial@01c28800 {
compatible = "snps,dw-apb-uart";
reg = <0x01c28800 0x400>;
interrupts = <GIC_SPI 2 IRQ_TYPE_LEVEL_HIGH>;
reg-shift = <2>;
reg-io-width = <4>;
clocks = <&ccu CLK_BUS_UART2>;
resets = <&ccu RST_BUS_UART2>;
status = "disabled";
};
i2c0: i2c@01c2ac00 {
compatible = "allwinner,sun6i-a31-i2c";
reg = <0x01c2ac00 0x400>;
interrupts = <GIC_SPI 6 IRQ_TYPE_LEVEL_HIGH>;
clocks = <&ccu CLK_BUS_I2C0>;
resets = <&ccu RST_BUS_I2C0>;
pinctrl-names = "default";
pinctrl-0 = <&i2c0_pins>;
status = "disabled";
#address-cells = <1>;
#size-cells = <0>;
};
i2c1: i2c@01c2b000 {
compatible = "allwinner,sun6i-a31-i2c";
reg = <0x01c2b000 0x400>;
interrupts = <GIC_SPI 7 IRQ_TYPE_LEVEL_HIGH>;
clocks = <&ccu CLK_BUS_I2C1>;
resets = <&ccu RST_BUS_I2C1>;
status = "disabled";
#address-cells = <1>;
#size-cells = <0>;
};
spi0: spi@1c68000 {
compatible = "allwinner,sun8i-h3-spi";
reg = <0x01c68000 0x1000>;
interrupts = <GIC_SPI 65 IRQ_TYPE_LEVEL_HIGH>;
clocks = <&ccu CLK_BUS_SPI0>, <&ccu CLK_SPI0>;
clock-names = "ahb", "mod";
pinctrl-names = "default";
pinctrl-0 = <&spi0_pins>;
resets = <&ccu RST_BUS_SPI0>;
status = "disabled";
#address-cells = <1>;
#size-cells = <0>;
};
gic: interrupt-controller@01c81000 { // interrupt-controller是独立字段，表示中断控制器。gic是其一个实例，地址在01c81000
compatible = "arm,cortex-a7-gic", "arm,cortex-a15-gic"; //驱动匹配
reg = <0x01c81000 0x1000>, //中断控制器的寄存器地址，和大小
<0x01c82000 0x1000>,
<0x01c84000 0x2000>,
<0x01c86000 0x2000>;
interrupt-controller;
#interrupt-cells = <3>; //调用该实例需要三个参数
interrupts = <GIC_PPI 9 (GIC_CPU_MASK_SIMPLE(4) | IRQ_TYPE_LEVEL_HIGH)>;
};
};
};
系统中的每个设备由device tree的一个节点来表示；
驱动代码¶
static struct of_device_id beep_table[] = {
{.compatible = "fs4412,beep"},
};
static struct platform_driver beep_driver=
{
.probe = beep_probe,
.remove = beep_remove,
.driver={
.name = "bigbang",
.of_match_table = beep_table,
},
};
设备树代码¶
fs4412-beep{
compatible = "fs4412,beep";
reg = <0x114000a0 0x4 0x139D0000 0x14>;
};
- compatible，关键属性，驱动中使用of_match_table，即of_device_id列表，其中就使用compatible字段来匹配设备。
简单地说就是，内核启动后会把设备树加载到树状结构体中，当insmod的时候，就会在树中查找匹配的设备节点来加载。
reg，描述寄存器基址和长度，可以有多个。
pwm: pwm@01c21400 {
compatible = "allwinner,sun8i-h3-pwm";
reg = <0x01c21400 0x8>;
clocks = <&osc24M>;
#pwm-cells = <3>;
status = "okay";
};
实例 : 类 @ 地址 {
compatible： “供应商, 设备id”
reg
clocks
}
基于设备树的driver的结构体的填充¶
static struct of_device_id beep_table[] = {
{.compatible = "fs4412,beep"},
};
static struct platform_driver beep_driver=
{
.probe = beep_probe,
.remove = beep_remove,
.driver={
.name = "bigbang",
.of_match_table = beep_table,
},
};
make dtbs 在内核根目录