学习设备树之（十一）Backlight

开发板：tiny4412SDK + S702 + 4GB Flash 
要移植的内核版本：Linux-4.4.0 （支持device tree） 
u-boot版本：友善之臂自带的 U-Boot 2010.12 
busybox版本：busybox 1.25

目标： 
由于 tiny4412 的lcd背光控制采用的一线触控，并不开源，因此移植友善自带的linux3.5 内核中的背光相关部分驱动程序。

原理图： 

设备树：

        backlight_demo@139D0000{                compatible         = "tiny4412,backlight_demo";                reg = <0x139D0000  0x14>;                tiny4412,backlight = <&gpx1 2 GPIO_ACTIVE_HIGH>;                pinctrl-names = "backlight_out","backlight_in";                pinctrl-0 = <&backlight_out>;                pinctrl-1 = <&backlight_in>;                interrupts = <0 40 0>;                clocks = <&clock CLK_PWM>;                clock-names = "timers";        };
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&pinctrl_1 {        backlight_out: backlight_out{                samsung,pins = "gpx1-2";                samsung,pin-function = <1>;                samsung,pin-pud = <0>;                samsung,pin-drv = <0>;        };         backlight_in: backlight_in{                samsung,pins = "gpx1-2";                samsung,pin-function = <0>;                samsung,pin-pud = <0>;                samsung,pin-drv = <0>;        };};
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代码：

//参考友善自带的 Tiny4412_1wire_host.c                                                                                 #include <linux/module.h>#include <linux/kernel.h>#include <linux/cdev.h>#include <linux/device.h>#include <linux/platform_device.h>#include <linux/gpio.h>#include <linux/of.h>#include <linux/of_gpio.h>#include <linux/fs.h>#include <asm/uaccess.h>#include <linux/bitops.h>#include <linux/clk.h>#include <linux/export.h>#include <linux/err.h>#include <linux/io.h>#include <linux/pwm.h>#include <linux/slab.h>#include <linux/spinlock.h>#include <linux/time.h>#include <linux/interrupt.h>#include <linux/delay.h>/*    PWM 时钟频率 100M    100M / 250 / 4 = 100000    1/100000 = 10us*/static int              major;static struct   cdev    backlight_cdev;static struct   class   *cls;static struct pinctrl   *pctrl;static struct pinctrl_state *pstate_in;static struct pinctrl_state *pstate_out;static int              one_write_pin;struct TIMER_BASE{    unsigned int TCFG0;    unsigned int TCFG1;    unsigned int TCON;    unsigned int TCNTB0;    unsigned int TCMPB0;    unsigned int TCNTO0;    unsigned int TCNTB1;    unsigned int TCMPB1;    unsigned int TCNTO1;    unsigned int TCNTB2;    unsigned int TCMPB2;    unsigned int TCNTO2;    unsigned int TCNTB3;    unsigned int TCMPB3;    unsigned int TCNTO3;    unsigned int TCNTB4;    unsigned int TCBTO4;    unsigned int TINT_CSTAT;};volatile static struct TIMER_BASE *timer = NULL;static volatile unsigned int io_bit_count;static volatile unsigned int io_data;enum{    IDLE,    START,    REQUEST,    WAITING,    RESPONSE,    STOPING,} one_wire_status = IDLE;static inline void stop_timer_for_1wire(void){    unsigned long tcon;    tcon = timer->TCON;    tcon &= ~(1 << 16);    timer->TCON = tcon;}static irqreturn_t timer_for_1wire_interrupt(int irq, void *dev_id){    unsigned int tint;    tint = timer->TINT_CSTAT;    tint |= 0x100;    timer->TINT_CSTAT = tint;    //printk("timer_for_1wire_interrupt\n");    io_bit_count--;    switch (one_wire_status)    {        case START:            if (io_bit_count == 0)            {                io_bit_count = 16;                one_wire_status = REQUEST;            }            break;        case REQUEST:            gpio_set_value(one_write_pin, io_data & (1U << 31));            io_data <<= 1;            if (io_bit_count == 0)            {                io_bit_count = 2;                one_wire_status = WAITING;            }            break;        case WAITING:            if (io_bit_count == 0)            {                io_bit_count = 32;                one_wire_status = RESPONSE;            }            if (io_bit_count == 1)            {                pinctrl_select_state(pctrl, pstate_in);                gpio_set_value(one_write_pin, 1);            }            break;        case RESPONSE:            io_data = (io_data << 1) | gpio_get_value(one_write_pin);            if (io_bit_count == 0)            {                io_bit_count = 2;                one_wire_status = STOPING;                gpio_set_value(one_write_pin, 1);                pinctrl_select_state(pctrl, pstate_out);                //one_wire_session_complete(one_wire_request, io_data);            }            break;        case STOPING:            if (io_bit_count == 0)            {                one_wire_status = IDLE;                stop_timer_for_1wire();            }            break;        default:            stop_timer_for_1wire();    }    return IRQ_HANDLED;}static const unsigned char crc8_tab[] ={    0x00, 0x07, 0x0E, 0x09, 0x1C, 0x1B, 0x12, 0x15,    0x38, 0x3F, 0x36, 0x31, 0x24, 0x23, 0x2A, 0x2D,    0x70, 0x77, 0x7E, 0x79, 0x6C, 0x6B, 0x62, 0x65,    0x48, 0x4F, 0x46, 0x41, 0x54, 0x53, 0x5A, 0x5D,    0xE0, 0xE7, 0xEE, 0xE9, 0xFC, 0xFB, 0xF2, 0xF5,    0xD8, 0xDF, 0xD6, 0xD1, 0xC4, 0xC3, 0xCA, 0xCD,    0x90, 0x97, 0x9E, 0x99, 0x8C, 0x8B, 0x82, 0x85,    0xA8, 0xAF, 0xA6, 0xA1, 0xB4, 0xB3, 0xBA, 0xBD,    0xC7, 0xC0, 0xC9, 0xCE, 0xDB, 0xDC, 0xD5, 0xD2,    0xFF, 0xF8, 0xF1, 0xF6, 0xE3, 0xE4, 0xED, 0xEA,    0xB7, 0xB0, 0xB9, 0xBE, 0xAB, 0xAC, 0xA5, 0xA2,    0x8F, 0x88, 0x81, 0x86, 0x93, 0x94, 0x9D, 0x9A,    0x27, 0x20, 0x29, 0x2E, 0x3B, 0x3C, 0x35, 0x32,    0x1F, 0x18, 0x11, 0x16, 0x03, 0x04, 0x0D, 0x0A,    0x57, 0x50, 0x59, 0x5E, 0x4B, 0x4C, 0x45, 0x42,    0x6F, 0x68, 0x61, 0x66, 0x73, 0x74, 0x7D, 0x7A,    0x89, 0x8E, 0x87, 0x80, 0x95, 0x92, 0x9B, 0x9C,    0xB1, 0xB6, 0xBF, 0xB8, 0xAD, 0xAA, 0xA3, 0xA4,    0xF9, 0xFE, 0xF7, 0xF0, 0xE5, 0xE2, 0xEB, 0xEC,    0xC1, 0xC6, 0xCF, 0xC8, 0xDD, 0xDA, 0xD3, 0xD4,    0x69, 0x6E, 0x67, 0x60, 0x75, 0x72, 0x7B, 0x7C,    0x51, 0x56, 0x5F, 0x58, 0x4D, 0x4A, 0x43, 0x44,    0x19, 0x1E, 0x17, 0x10, 0x05, 0x02, 0x0B, 0x0C,    0x21, 0x26, 0x2F, 0x28, 0x3D, 0x3A, 0x33, 0x34,    0x4E, 0x49, 0x40, 0x47, 0x52, 0x55, 0x5C, 0x5B,    0x76, 0x71, 0x78, 0x7F, 0x6A, 0x6D, 0x64, 0x63,    0x3E, 0x39, 0x30, 0x37, 0x22, 0x25, 0x2C, 0x2B,    0x06, 0x01, 0x08, 0x0F, 0x1A, 0x1D, 0x14, 0x13,    0xAE, 0xA9, 0xA0, 0xA7, 0xB2, 0xB5, 0xBC, 0xBB,    0x96, 0x91, 0x98, 0x9F, 0x8A, 0x8D, 0x84, 0x83,    0xDE, 0xD9, 0xD0, 0xD7, 0xC2, 0xC5, 0xCC, 0xCB,    0xE6, 0xE1, 0xE8, 0xEF, 0xFA, 0xFD, 0xF4, 0xF3,};#define crc8_init(crc) ((crc) = 0XACU)#define crc8(crc, v) ( (crc) = crc8_tab[(crc) ^(v)])static void start_one_wire_session(unsigned char req){    unsigned int tcon;    printk("backlight_write\n");    one_wire_status = START;    gpio_set_value(one_write_pin, 1);    pinctrl_select_state(pctrl, pstate_out);    // IDLE to START    {        unsigned char crc;        crc8_init(crc);        crc8(crc, req);        io_data = (req << 8) + crc;        io_data <<= 16;    }    io_bit_count = 1;    pinctrl_select_state(pctrl, pstate_out);    timer->TCNTB3 = 650;    //init tranfer and start timer    tcon = timer->TCON;    tcon &= ~(0xF << 16);    tcon |= (1 << 17);    timer->TCON = tcon;    tcon |= (1 << 16);    tcon |= (1 << 19);    tcon &= ~(1 << 17);    timer->TCON = tcon;    timer->TINT_CSTAT |= 0x08;    gpio_set_value(one_write_pin, 0);}static ssize_t backlight_write(struct file *file, const char __user *buf, size_t count, loff_t *off){    unsigned char reg, ret;    ret = copy_from_user(&reg, buf, 1);    if (ret < 0)    {        printk("%s copy_from_user error\n", __func__);    }    if (reg > 127)        { reg = 127; }    start_one_wire_session(reg + 0x80);    return 1;}static int backlight_open(struct inode *inode, struct file *file){    printk("backlight_open\n");    return 0;}static int backlight_release(struct inode *inode, struct file *file){    printk("backlight_exit\n");    return 0;}static struct file_operations backlight_fops ={    .owner              = THIS_MODULE,    .open               = backlight_open,    .release            = backlight_release,    .write              = backlight_write,};static struct device *dev;static struct clk *base_clk;static struct resource *res = NULL, *irq = NULL;static int backlight_probe(struct platform_device *pdev){    int ret;    dev_t devid;    dev = &pdev->dev;    printk("enter %s\n", __func__);    pctrl = devm_pinctrl_get(dev);    if (pctrl == NULL)    {        printk("devm_pinctrl_get error\n");        return -EINVAL;    }    pstate_in  = pinctrl_lookup_state(pctrl, "backlight_in");    pstate_out = pinctrl_lookup_state(pctrl, "backlight_out");    if (pstate_in == NULL || pstate_out == NULL)    {        printk("pinctrl_lookup_state error\n");        return -EINVAL;    }    one_write_pin = of_get_named_gpio(dev->of_node, "tiny4412,backlight", 0);    if (!one_write_pin)    {        printk("of_get_named_gpio error\n");        return -EINVAL;    }    devm_gpio_request_one(dev, one_write_pin, GPIOF_OUT_INIT_HIGH, "one_write");    //pinctrl_select_state(pctrl, pstate);    res = platform_get_resource(pdev, IORESOURCE_MEM, 0);    if (res == NULL)    {        printk("platform_get_resource error\n");        return -EINVAL;    }    base_clk = devm_clk_get(&pdev->dev, "timers");    if (IS_ERR(base_clk))    {        dev_err(dev, "failed to get timer base clk\n");        return PTR_ERR(base_clk);    }    ret = clk_prepare_enable(base_clk);    if (ret < 0)    {        dev_err(dev, "failed to enable base clock\n");        return ret;    }    timer = devm_ioremap_resource(&pdev->dev, res);    if (timer == NULL)    {        printk("devm_ioremap_resource error\n");        return -EINVAL;    }    printk("timer: %x\n", (unsigned int)timer);    timer->TCFG0  = 0xf00;    timer->TCFG1  = 0x10004;    irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);    if (irq == NULL)    {        printk("platform_get_resource irq error\n");        return -EINVAL;    }    ret = devm_request_irq(dev, irq->start, timer_for_1wire_interrupt , IRQF_TIMER, "backlight", NULL);    if (ret)    {        dev_err(dev, "unable to request irq\n");        return -EINVAL;    }    start_one_wire_session(0x60);    if (alloc_chrdev_region(&devid, 0, 1, "backlight") < 0)    {        printk("%s ERROR\n", __func__);        return -EINVAL;    }    major = MAJOR(devid);    cdev_init(&backlight_cdev, &backlight_fops);    cdev_add(&backlight_cdev, devid, 1);    cls = class_create(THIS_MODULE, "backlight_demo");    device_create(cls, NULL, MKDEV(major, 0), NULL, "backlight");    return 0;}static int backlight_remove(struct platform_device *pdev){    printk("enter %s\n", __func__);    device_destroy(cls, MKDEV(major, 0));    class_destroy(cls);    cdev_del(&backlight_cdev);    unregister_chrdev_region(MKDEV(major, 0), 1);    devm_pinctrl_put(pctrl);    devm_free_irq(dev, irq->start, NULL);    clk_disable_unprepare(base_clk);    devm_gpio_free(dev, one_write_pin);    return 0;}static const struct of_device_id backlight_dt_ids[] ={    { .compatible = "tiny4412,backlight_demo", },    {},};MODULE_DEVICE_TABLE(of, backlight_dt_ids);static struct platform_driver backlight_driver ={    .driver        = {        .name      = "backlight_demo",        .of_match_table    = of_match_ptr(backlight_dt_ids),    },    .probe         = backlight_probe,    .remove        = backlight_remove,};static int backlight_init(void){    int ret;    printk("enter %s\n", __func__);    ret = platform_driver_register(&backlight_driver);    if (ret)    {        printk(KERN_ERR "backlight demo: probe faid backlight: %d\n", ret);    }    return ret;}static void backlight_exit(void){    printk("enter %s\n", __func__);    platform_driver_unregister(&backlight_driver);}module_init(backlight_init);module_exit(backlight_exit);MODULE_LICENSE("GPL");