rk3399下pwm驅動
阿新 • • 發佈：2018-11-09
現在記錄一下rk3399下pwm的驅動編寫，下面是核心pwm的API，從開源論壇複製（瑞芯微的開源論壇裡面的Wiki教程）
(1)、在要使用 PWM 控制的裝置驅動檔案中包含以下標頭檔案： #include <linux/pwm.h> 該標頭檔案主要包含 PWM 的函式介面。 (2)、申請 PWM使用 struct pwm_device *pwm_request(int pwm_id, const char *label); 函式申請 PWM。 例如： struct pwm_device * pwm1 = NULL;pwm0 = pwm_request(1, “firefly-pwm”); (3)、配置 PWM使用 int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns); 配置 PWM 的佔空比， 例如： pwm_config(pwm0, 500000, 1000000)； (4)、使能PWM 函式 int pwm_enable(struct pwm_device *pwm); 用於使能 PWM，例如： pwm_enable(pwm0); (5)控制 PWM 輸出主要使用以下介面函式： struct pwm_device *pwm_request(int pwm_id, const char *label); 功能：用於申請 pwm void pwm_free(struct pwm_device *pwm); 功能：用於釋放所申請的 pwm int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns); 功能：用於配置 pwm 的佔空比 int pwm_enable(struct pwm_device *pwm); 功能：使能 pwm void pwm_disable(struct pwm_device *pwm); 功能：禁止 pwm
編寫該驅動程式的幾個流程：
1.在裝置樹下新增相應內容，內容如下：
pwm_demo{
status = "okay";
compatible = "pwm_test";
buzzer-gpio = <&gpio4 18 GPIO_ACTIVE_LOW>;
};
經測試，gpio一項完全可以不要，compatible為匹配條件，另外在/kernel/arch/arm64/boot/dts/rockchip目錄下使用grep "pwm" * -nR命令，搜尋結果如下：（關鍵的內容）
Binary file g3399-development-board.dtb matches
g3399-development-board.dts:234:&pwm3 {
g3399-development-board.dts:237: compatible = "rockchip,remotectl-pwm";
g3399-development-board.dts:238: remote_pwm_id = <3>;
rk3399.dtsi:1234: pwm0: [email protected] {
rk3399.dtsi:1235: compatible = "rockchip,rk3399-pwm", "rockchip,rk3288-pwm";
rk3399.dtsi:1237: #pwm-cells = <3>;
rk3399.dtsi:1239: pinctrl-0 = <&pwm0_pin>;
rk3399.dtsi:1241: clock-names = "pwm";
rk3399.dtsi:1245: pwm1: 然後開啟rk3399.dtsi，內容如下：（sudo vim rk3399.dtsi）然後搜尋，在終端輸入 ：/pwm
pwm0: [email protected] {
compatible = "rockchip,rk3399-pwm", "rockchip,rk3288-pwm";
reg = <0x0 0xff420000 0x0 0x10>;
#pwm-cells = <3>;
pinctrl-names = "default";
pinctrl-0 = <&pwm0_pin>;
clocks = <&pmucru PCLK_RKPWM_PMU>;
clock-names = "pwm";
status = "disabled";
};
pwm1: [email protected] {
compatible = "rockchip,rk3399-pwm", "rockchip,rk3288-pwm";
reg = <0x0 0xff420010 0x0 0x10>;
#pwm-cells = <3>;
pinctrl-names = "default";
pinctrl-0 = <&pwm1_pin>;
clocks = <&pmucru PCLK_RKPWM_PMU>;
clock-names = "pwm";
status = "disabled";
};
.......................
此處省略n行程式碼可以看到：status = "disabled";
這裡我使用的pwm1 所以pwm1下面的status = "disabled";改為status = "okay";
現在是新增自己的內容了，我在該目錄下的g3399-baseboard.dtsi檔案中新增如下內容：
pwm_demo{
status = "okay";
compatible = "pwm_test";
buzzer-gpio = <&gpio4 18 GPIO_ACTIVE_LOW>;
};
現在第一步就結束了
2.編寫裝置驅動及Makefile：
#include<linux/pwm.h>
#include <linux/moduleparam.h>
#include <linux/stat.h>
#include <linux/kernel.h>
#include <linux/gpio.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/of.h>
#include <linux/of_gpio.h>
#include <linux/of_platform.h>
#include <linux/version.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/pm.h>
#include <linux/sysctl.h>
#include <linux/proc_fs.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#define GPIO_LOW 0
#define GPIO_HIGH 1
struct pwm_device *pwm = NULL;
int major;
int gpio;
static struct class *cls;
static ulong arg1;
static int arg2=0;
module_param(arg1,ulong,S_IRUSR);
module_param(arg2,int,S_IRUSR);
static int pwm_open(struct inode *inode, struct file *file)
{
printk(KERN_EMERG "%s-%d: enter\n",__FUNCTION__,__LINE__);
return 0;
}
static struct file_operations pwm_fops = {
.owner = THIS_MODULE,
.open = pwm_open,
};
static int pwm_probe(struct platform_device *pdev)
{
int ret;
enum of_gpio_flags flag;
struct device_node *led_node = pdev->dev.of_node;
major = register_chrdev(0, "pwm_test", &pwm_fops);
cls = class_create(THIS_MODULE, "pwm_test");
device_create(cls, NULL, MKDEV(major, 0), NULL, "pwm_buzzer");
gpio = of_get_named_gpio_flags(led_node,"buzzer-gpio", 0,&flag);
if (!gpio_is_valid(gpio)){
printk(KERN_INFO "hello: invalid gpio : %d\n",gpio);
return -1;
}
ret = gpio_request(gpio, "buzzer");
if (ret) {
gpio_free(gpio);
return -EIO;
}
gpio_direction_output(gpio, GPIO_HIGH);
gpio_set_value(gpio,arg2);
pwm = pwm_request(1,"pwm");
if(IS_ERR(pwm)){
dev_err(&pdev->dev,"unable to request pwm\n");
printk("pwm err %ld\n",PTR_ERR(pwm));
}
pwm_config(pwm,arg1,100000);
pwm_enable(pwm);
printk(KERN_INFO "pwm sucess\n");
return 0;
}
static struct of_device_id pwm_of_match[] = {
{ .compatible = "pwm_test"},
{}
};
static int pwm_remove(struct platform_device *pdev)
{
gpio_free(gpio);
device_destroy(cls, MKDEV(major, 0));
class_destroy(cls);
unregister_chrdev(major, "pwm_test");
pwm_free(pwm);
return 0;
}
static struct platform_driver pwm_driver={
.driver = {
.name ="pwm",
.owner =THIS_MODULE,
.of_match_table = pwm_of_match,
},
.probe = pwm_probe,
.remove = pwm_remove,
};
static int __init pwm_init(void)
{
printk(KERN_INFO "Enter %s\n", __FUNCTION__);
return platform_driver_register(&pwm_driver);
return 0;
}
static void __exit pwm_exit(void)
{
platform_driver_unregister(&pwm_driver);
printk(KERN_INFO "Exit pwm_driver\n");
}
module_init(pwm_init);
module_exit(pwm_exit);
MODULE_LICENSE("GPL");#!/bin/bash
obj-m += pwm.o
KDIR := /rk3399/source/g3399-v7-1-2-20180529/kernel
PWD ?= $(shell pwd)
all:
make -C $(KDIR) M=$(PWD) modules
clean:
rm -rf *.o *.ko
到此，結束。
使用ls /dev 命令可以看到自己生成的裝置結點，另附上本驅動載入命令： insmod pwm.ko arg1=80000 arg2=0