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  • I.MX6 PWM buzzer driver hacking with Demo test

    /*****************************************************************************
     *             I.MX6 PWM buzzer driver hacking with Demo test
     * 声明:
     *     1. I.MX6和OK335xS实现PWM驱动函数是不一样的;
     *     2. 通过分析PWM驱动,了解有哪些驱动函数可以用;
     *     3. 使用I.MX6提供的PWM函数,编写测试用例buzzer驱动;
     *     4. 使用C编写测试程序。
     *
     *                                     2015-10-20 晴 深圳 南山平山村 曾剑锋
     ****************************************************************************/
    
                    \\\\\\-*- 目录 -*-/////////////
                    |  一、cat arch/arm/plat-mxc/pwm.c
                    |  二、cat driver/misc/pwm_buzzer.c
                    |  三、cat main.c (demo test)
                    --------------------------------------
    
    一、cat arch/arm/plat-mxc/pwm.c
        /*
         * simple driver for PWM (Pulse Width Modulator) controller
         *
         * This program is free software; you can redistribute it and/or modify
         * it under the terms of the GNU General Public License version 2 as
         * published by the Free Software Foundation.
         *
         * Derived from pxa PWM driver by eric miao <eric.miao@marvell.com>
         * Copyright 2009-2013 Freescale Semiconductor, Inc. All Rights Reserved.
         */
        
        #include <linux/module.h>
        #include <linux/kernel.h>
        #include <linux/platform_device.h>
        #include <linux/slab.h>
        #include <linux/err.h>
        #include <linux/clk.h>
        #include <linux/io.h>
        #include <linux/pwm.h>
        #include <linux/fsl_devices.h>
        #include <mach/hardware.h>
        
        
        /* i.MX1 and i.MX21 share the same PWM function block: */
        
        #define MX1_PWMC    0x00   /* PWM Control Register */
        #define MX1_PWMS    0x04   /* PWM Sample Register */
        #define MX1_PWMP    0x08   /* PWM Period Register */
        
        
        /* i.MX27, i.MX31, i.MX35 share the same PWM function block: */
        
        #define MX3_PWMCR                 0x00    /* PWM Control Register */
        #define MX3_PWMSAR                0x0C    /* PWM Sample Register */
        #define MX3_PWMPR                 0x10    /* PWM Period Register */
        #define MX3_PWMCR_PRESCALER(x)      (((x - 1) & 0xFFF) << 4)
        #define MX3_PWMCR_DOZEEN            (1 << 24)
        #define MX3_PWMCR_WAITEN            (1 << 23)
        #define MX3_PWMCR_DBGEN                (1 << 22)
        #define MX3_PWMCR_CLKSRC_IPG_HIGH   (2 << 16)
        #define MX3_PWMCR_CLKSRC_IPG        (1 << 16)
        #define MX3_PWMCR_SWR               (1 << 3)
        #define MX3_PWMCR_EN                (1 << 0)
        
        #define MX3_PWMCR_STOPEN            (1 << 25)
        #define MX3_PWMCR_DOZEEN            (1 << 24)
        #define MX3_PWMCR_WAITEN            (1 << 23)
        #define MX3_PWMCR_DBGEN                (1 << 22)
        #define MX3_PWMCR_CLKSRC_IPG        (1 << 16)
        #define MX3_PWMCR_CLKSRC_IPG_32k    (3 << 16)
        
        struct pwm_device {
            struct list_head    node;
            struct platform_device *pdev;
        
            const char    *label;
            struct clk    *clk;
        
            int        clk_enabled;
            void __iomem    *mmio_base;
        
            unsigned int    use_count;
            unsigned int    pwm_id;
            int        pwmo_invert;
            void (*enable_pwm_pad)(void);
            void (*disable_pwm_pad)(void);
        };
        
        /**
         * 1. 操作PWM用到duty(duty_ns)、period(period_ns)2个参数;
         * 2. period就是频率参数(周期时间),duty为占空比;
         * 3. period和duty的参数单位为纳秒(ns);
         * 4. 1s=1000ms=1000000us=1000000000ns;
         * 5. period最大的取值范围为0—1000000000,而duty则取值0—period值之间;
         * 6. 平时我们可能更喜欢使用频率(Hz)来表示period,占空比来表示duty;
         */
        int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
        {
            if (pwm == NULL || period_ns == 0 || duty_ns > period_ns)
                return -EINVAL;
        
            if (!(cpu_is_mx1() || cpu_is_mx21())) {
                unsigned long long c;
                unsigned long period_cycles, duty_cycles, prescale;
                u32 cr;
        
                if (pwm->pwmo_invert)
                    duty_ns = period_ns - duty_ns;
        
                c = clk_get_rate(pwm->clk);
                c = c * period_ns;
                do_div(c, 1000000000);
                period_cycles = c;
        
                prescale = period_cycles / 0x10000 + 1;
        
                period_cycles /= prescale;
                c = (unsigned long long)period_cycles * duty_ns;
                do_div(c, period_ns);
                duty_cycles = c;
        
                /*
                 * according to imx pwm RM, the real period value should be
                 * PERIOD value in PWMPR plus 2.
                 */
                if (period_cycles > 2)
                    period_cycles -= 2;
                else
                    period_cycles = 0;
        
                writel(duty_cycles, pwm->mmio_base + MX3_PWMSAR);
                writel(period_cycles, pwm->mmio_base + MX3_PWMPR);
        
                cr = MX3_PWMCR_PRESCALER(prescale) |
                    MX3_PWMCR_STOPEN | MX3_PWMCR_DOZEEN |
                    MX3_PWMCR_WAITEN | MX3_PWMCR_DBGEN;
        
                if (cpu_is_mx25())
                    cr |= MX3_PWMCR_CLKSRC_IPG;
                else
                    cr |= MX3_PWMCR_CLKSRC_IPG_HIGH;
        
                writel(cr, pwm->mmio_base + MX3_PWMCR);
            } else if (cpu_is_mx1() || cpu_is_mx21()) {
                /* The PWM subsystem allows for exact frequencies. However,
                 * I cannot connect a scope on my device to the PWM line and
                 * thus cannot provide the program the PWM controller
                 * exactly. Instead, I'm relying on the fact that the
                 * Bootloader (u-boot or WinCE+haret) has programmed the PWM
                 * function group already. So I'll just modify the PWM sample
                 * register to follow the ratio of duty_ns vs. period_ns
                 * accordingly.
                 *
                 * This is good enough for programming the brightness of
                 * the LCD backlight.
                 *
                 * The real implementation would divide PERCLK[0] first by
                 * both the prescaler (/1 .. /128) and then by CLKSEL
                 * (/2 .. /16).
                 */
                u32 max = readl(pwm->mmio_base + MX1_PWMP);
                u32 p;
                if (pwm->pwmo_invert)
                    duty_ns = period_ns - duty_ns;
                p = max * duty_ns / period_ns;
                writel(max - p, pwm->mmio_base + MX1_PWMS);
            } else {
                BUG();
            }
        
            return 0;
        }
        EXPORT_SYMBOL(pwm_config);
        
        /**
         * 使能pwm
         */
        int pwm_enable(struct pwm_device *pwm)
        {
            unsigned long reg;
            int rc = 0;
        
            if (!pwm->clk_enabled) {
                rc = clk_enable(pwm->clk);
                if (!rc)
                    pwm->clk_enabled = 1;
            }
        
            reg = readl(pwm->mmio_base + MX3_PWMCR);
            reg |= MX3_PWMCR_EN;
            writel(reg, pwm->mmio_base + MX3_PWMCR);
        
            if (pwm->enable_pwm_pad)
                pwm->enable_pwm_pad();
        
            return rc;
        }
        EXPORT_SYMBOL(pwm_enable);
        
        /**
         * 关闭pwm
         */
        void pwm_disable(struct pwm_device *pwm)
        {
            if (pwm->disable_pwm_pad)
                pwm->disable_pwm_pad();
        
            writel(MX3_PWMCR_SWR, pwm->mmio_base + MX3_PWMCR);
            while (readl(pwm->mmio_base + MX3_PWMCR) & MX3_PWMCR_SWR)
                ;
        
            if (pwm->clk_enabled) {
                clk_disable(pwm->clk);
                pwm->clk_enabled = 0;
            }
        }
        EXPORT_SYMBOL(pwm_disable);
        
        static DEFINE_MUTEX(pwm_lock);
        static LIST_HEAD(pwm_list);
        
        /**
         * 通过pwm的id来表示申请pwm通道,label只是表示其名字,名字可以随意取
         */
        struct pwm_device *pwm_request(int pwm_id, const char *label)
        {
            struct pwm_device *pwm;
            int found = 0;
        
            mutex_lock(&pwm_lock);
        
            list_for_each_entry(pwm, &pwm_list, node) {
                if (pwm->pwm_id == pwm_id) {
                    found = 1;
                    break;
                }
            }
        
            if (found) {
                if (pwm->use_count == 0) {
                    pwm->use_count++;
                    pwm->label = label;
                } else
                    pwm = ERR_PTR(-EBUSY);
            } else
                pwm = ERR_PTR(-ENOENT);
        
            mutex_unlock(&pwm_lock);
            return pwm;
        }
        EXPORT_SYMBOL(pwm_request);
        
        /**
         * 前面申请了pwm,通过这个函数来释放pwm
         */
        void pwm_free(struct pwm_device *pwm)
        {
            mutex_lock(&pwm_lock);
        
            if (pwm->use_count) {
                pwm->use_count--;
                pwm->label = NULL;
            } else
                pr_warning("PWM device already freed
    ");
        
            mutex_unlock(&pwm_lock);
        }
        EXPORT_SYMBOL(pwm_free);
        
        /**
         * 这里是pwm控制器注册函数
         */
        static int __devinit mxc_pwm_probe(struct platform_device *pdev)
        {
            struct pwm_device *pwm;
            struct resource *r;
            struct mxc_pwm_platform_data *plat_data = pdev->dev.platform_data;
            int ret = 0;
        
            pwm = kzalloc(sizeof(struct pwm_device), GFP_KERNEL);
            if (pwm == NULL) {
                dev_err(&pdev->dev, "failed to allocate memory
    ");
                return -ENOMEM;
            }
        
            pwm->clk = clk_get(&pdev->dev, "pwm");
        
            if (IS_ERR(pwm->clk)) {
                ret = PTR_ERR(pwm->clk);
                goto err_free;
            }
        
            pwm->clk_enabled = 0;
        
            pwm->use_count = 0;
            pwm->pwm_id = pdev->id;
            pwm->pdev = pdev;
            if (plat_data != NULL) {
                pwm->pwmo_invert = plat_data->pwmo_invert;
                pwm->enable_pwm_pad = plat_data->enable_pwm_pad;
                pwm->disable_pwm_pad = plat_data->disable_pwm_pad;
            }
        
            r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
            if (r == NULL) {
                dev_err(&pdev->dev, "no memory resource defined
    ");
                ret = -ENODEV;
                goto err_free_clk;
            }
        
            r = request_mem_region(r->start, r->end - r->start + 1, pdev->name);
            if (r == NULL) {
                dev_err(&pdev->dev, "failed to request memory resource
    ");
                ret = -EBUSY;
                goto err_free_clk;
            }
        
            pwm->mmio_base = ioremap(r->start, r->end - r->start + 1);
            if (pwm->mmio_base == NULL) {
                dev_err(&pdev->dev, "failed to ioremap() registers
    ");
                ret = -ENODEV;
                goto err_free_mem;
            }
        
            mutex_lock(&pwm_lock);
            list_add_tail(&pwm->node, &pwm_list);
            mutex_unlock(&pwm_lock);
        
            platform_set_drvdata(pdev, pwm);
            return 0;
        
        err_free_mem:
            release_mem_region(r->start, r->end - r->start + 1);
        err_free_clk:
            clk_put(pwm->clk);
        err_free:
            kfree(pwm);
            return ret;
        }
        
        static int __devexit mxc_pwm_remove(struct platform_device *pdev)
        {
            struct pwm_device *pwm;
            struct resource *r;
        
            pwm = platform_get_drvdata(pdev);
            if (pwm == NULL)
                return -ENODEV;
        
            mutex_lock(&pwm_lock);
            list_del(&pwm->node);
            mutex_unlock(&pwm_lock);
        
            iounmap(pwm->mmio_base);
        
            r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
            release_mem_region(r->start, r->end - r->start + 1);
        
            clk_put(pwm->clk);
        
            kfree(pwm);
            return 0;
        }
        
        static struct platform_driver mxc_pwm_driver = {
            .driver        = {
                .name    = "mxc_pwm",
            },
            .probe        = mxc_pwm_probe,
            .remove        = __devexit_p(mxc_pwm_remove),
        };
        
        static int __init mxc_pwm_init(void)
        {
            return platform_driver_register(&mxc_pwm_driver);
        }
        arch_initcall(mxc_pwm_init);
        
        static void __exit mxc_pwm_exit(void)
        {
            platform_driver_unregister(&mxc_pwm_driver);
        }
        module_exit(mxc_pwm_exit);
        
        MODULE_LICENSE("GPL v2");
        MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");
    
    二、cat driver/misc/pwm_buzzer.c
        #include <linux/init.h>
        #include <linux/module.h>
        #include <linux/moduleparam.h>
        #include <linux/errno.h>
        #include <linux/miscdevice.h>
        #include <linux/types.h>
        #include <linux/io.h>
        #include <linux/pwm.h>
        #include <linux/fs.h>  
        
        #define BUZZER_FREQENCY 1
        #define DEV_NAME    "buzzer"
        
        /*pwm for this buzzer*/
        struct pwm_device *pwm = NULL;
        
        static int buzzer_open(struct inode *inode, struct file *filp)
        {
        
            if(pwm != NULL)
                return -EBUSY;
        
            /**
             * buzzer正好挂载在I.MX6的pwm4上,所以这里申请3号(从零开始算)PWM
             */
            pwm = pwm_request(3, "buzzer");
            if ( pwm == NULL ) {
                printk("buzzer open error.
    ");
            }
        
            return 0;
        }
        
        static int buzzer_release(struct inode *inode, struct file *filp)
        {
            pwm_disable(pwm);               // 关闭pwm
            pwm_free(pwm);                  // 释放pwm
            pwm = NULL;
        
            return 0;
        }
        
        static long buzzer_ioctl(struct file *filp,
                                unsigned int cmd, unsigned long arg)
        {
            if(pwm == NULL)
                return -EINVAL;
        
            if(arg > 20000 || arg < 0)
                return -EINVAL;
        
            switch (cmd) {
            case BUZZER_FREQENCY:
                if(arg==0)
                    pwm_disable(pwm);
                else
                {
                    pwm_config(pwm, 1000000000/arg/2, 1000000000/arg);
                    pwm_enable(pwm);
                }
                break;
            default:
                break;
            }
        
            return 0;
        }
        
        static struct file_operations buzzer_fops = {
            .owner              = THIS_MODULE,
            .unlocked_ioctl     = buzzer_ioctl,
            .open               = buzzer_open,
            .release            = buzzer_release,
        };
        
        static struct miscdevice buzzer_miscdev =
        {
             .minor  = MISC_DYNAMIC_MINOR,
             .name   = DEV_NAME,
             .fops   = &buzzer_fops,
        };
        
        static int __init buzzer_init(void)
        {
            printk(" zengjf check buzzer init.
    ");
            misc_register(&buzzer_miscdev);
            return 0;
        }
        
        static void __exit buzzer_exit(void)
        {
           misc_deregister(&buzzer_miscdev);
        }
        
        module_init(buzzer_init);
        module_exit(buzzer_exit);
        
        MODULE_DESCRIPTION("pwm_buzzer driver");
        MODULE_LICENSE("GPL");
    
    三、cat main.c (demo test)
        ......
        #define PWM_IOCTL_SET_FREQ  1
        #define PWM_IOCTL_STOP      0
        ......
        int fd = open("dev/buzzer", O_RDWR);
        ......
        // 传入频率2000Hz
        ioctl(fd, PWM_IOCTL_SET_FREQ, 2000);
        ......
        ioctl(fd, PWM_IOCTL_STOP);
        ......
        close(fd);
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  • 原文地址:https://www.cnblogs.com/zengjfgit/p/4895161.html
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