设备树的pwm节点：

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// vi rk3399.dtsi:
pwm0: pwm@ff420000 {
        compatible = "rockchip,rk3399-pwm", "rockchip,rk3288-pwm";
        reg = <0x0 0xff420000 0x0 0x10>;
        #pwm-cells = <3>;
        pinctrl-names = "active";
        pinctrl-0 = <&pwm0_pin>;
        clocks = <&pmucru PCLK_RKPWM_PMU>;
        clock-names = "pwm";
        status = "okay";
};

这个设备树节点会和pwm-rockchip.c匹配，调用probe函数：

根据设备树的信息，配置pwm的底层寄存器，把每个pwm通道都编一个index索引值都放入一个链表。以后我们要用某个pwm端口的时候就直接request端口就行了。

pwm使用实例：

修改设备树：

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 pwm_demo: pwm_demo {
        status = "okay";
        compatible = "firefly,rk3399-pwm";
        pwm_id = <0>;      //使用pwm0通道
        min_period = <0>;
        max_period = <10000>;
        duty_ns = <5000>;
};

编写驱动程序：

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#include <linux/iio/types.h>
#include <linux/input.h>
#include <linux/input-polldev.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/property.h>
#include <linux/slab.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/gpio.h>
#include <linux/gpio/consumer.h>
#include <linux/iio/consumer.h>
#include <linux/interrupt.h>
#include <linux/pinctrl/consumer.h>

#include <linux/pwm.h>

static struct pwm_device * pwm_device = NULL;

static int firefly_pwm_probe(struct platform_device *pdev)
{
	int ret;
	
    printk("firefly_pwm_probe!\n");
	pwm_device = pwm_request(0, "firefly-pwm");
	ret = pwm_config(pwm_device, 500000, 1000000);
	ret = pwm_enable(pwm_device);

     return 0;
}

static int firefly_pwm_remove(struct platform_device *pdev)
{
	printk("%s %s %d\n", __FILE__, __FUNCTION__, __LINE__);
	
	pwm_disable(pwm_device);
	return 0;
}

static const struct of_device_id firefly_pwm_match[] = {
     { .compatible = "firefly,rk3399-pwm" },
     {},
};

static struct platform_driver firefly_pwm_driver = {
    .probe      = firefly_pwm_probe,
    .remove     = firefly_pwm_remove,
    .driver     = {
        .name   = "firefly_pwm",
        .owner  = THIS_MODULE,
        .of_match_table = firefly_pwm_match,
        },
};

static int __init firefly_pwm_init(void)
{
	printk("%s %s %d\n", __FILE__, __FUNCTION__, __LINE__);
	return platform_driver_register(&firefly_pwm_driver);
}

static void __exit firefly_pwm_exit(void)
{
	printk("%s %s %d\n", __FILE__, __FUNCTION__, __LINE__);
	platform_driver_unregister(&firefly_pwm_driver);
}

module_init(firefly_pwm_init);
module_exit(firefly_pwm_exit);

MODULE_LICENSE("GPL");