s3c2410 touchscreen 驱动分析

 linux/drivers/input/touchscreen/s3c2410_ts.c

大体工作过程：

在probe中通过platform_get_irq 将touchscreen的中断源注册好，并和stylus_irq绑定

当触摸版被按下是，触法中断，调用stylus_irq --> s3c_adc_start 激活采样队列

adc采样完成后，会引发s3c_adc_irq 中断

s3c_adc_irq -->s3c24xx_ts_select --> select =1 -->continue

=0 -->mod_timer -->touch_timer --> touch_timer_fire

#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/gpio.h>
#include <linux/input.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/platform_device.h>
#include <linux/clk.h>
#include <linux/io.h>

#include <plat/adc.h>
#include <plat/regs-adc.h>
#include <plat/ts.h>

#define TSC_SLEEP  (S3C2410_ADCTSC_PULL_UP_DISABLE | S3C2410_ADCTSC_XY_PST(0))

#define INT_DOWN        (0)
#define INT_UP          (1 << 8)

#define WAIT4INT        (S3C2410_ADCTSC_YM_SEN | \
                         S3C2410_ADCTSC_YP_SEN | \
                         S3C2410_ADCTSC_XP_SEN | \
                         S3C2410_ADCTSC_XY_PST(3))

#define AUTOPST         (S3C2410_ADCTSC_YM_SEN | \
                         S3C2410_ADCTSC_YP_SEN | \
                         S3C2410_ADCTSC_XP_SEN | \
                         S3C2410_ADCTSC_AUTO_PST | \
                         S3C2410_ADCTSC_XY_PST(0))

#define FEAT_PEN_IRQ    (1 << 0)        /* HAS ADCCLRINTPNDNUP */

struct s3c2410ts  ---触摸板核心数据结构
/* Per-touchscreen data. */

/**
 * struct s3c2410ts - driver touchscreen state.
 * @client: The ADC client we registered with the core driver.
 * @dev: The device we are bound to.
 * @input: The input device we registered with the input subsystem.
 * @clock: The clock for the adc.
 * @io: Pointer to the IO base.
 * @xp: The accumulated X position data.
 * @yp: The accumulated Y position data.
 * @irq_tc: The interrupt number for pen up/down interrupt
 * @count: The number of samples collected.
 * @shift: The log2 of the maximum count to read in one go.
 * @features: The features supported by the TSADC MOdule.
 */
struct s3c2410ts {
        struct s3c_adc_client *client;
        struct device *dev;
        struct input_dev *input;
        struct clk *clock;
        void __iomem *io;
        unsigned long xp;
        unsigned long yp;
        int irq_tc;
        int count;
        int shift;
        int features;
};

static struct s3c2410ts ts;

/**
 * get_down - return the down state of the pen
 * @data0: The data read from ADCDAT0 register.
 * @data1: The data read from ADCDAT1 register.
 *
 * Return non-zero if both readings show that the pen is down.
 */

判断触摸板是否被按下

static inline bool get_down(unsigned long data0, unsigned long data1)
{
        /* returns true if both data values show stylus down */
        return (!(data0 & S3C2410_ADCDAT0_UPDOWN) &&
                !(data1 & S3C2410_ADCDAT0_UPDOWN)); //s3c2410 的ADCDATA0和ADCDATA1的第8位是判断是否有被按下的寄存器
}

static void touch_timer_fire(unsigned long data)
{
        unsigned long data0;
        unsigned long data1;
        bool down;

        data0 = readl(ts.io + S3C2410_ADCDAT0);
        data1 = readl(ts.io + S3C2410_ADCDAT1);

        down = get_down(data0, data1);

        if (down) {
                if (ts.count == (1 << ts.shift)) { //再次判断是否完全转化完
                     

用移位的方法求平均值 

ts.xp >>= ts.shift;
                        ts.yp >>= ts.shift;

                        dev_dbg(ts.dev, "%s: X=%lu, Y=%lu, count=%d\n",
                                __func__, ts.xp, ts.yp, ts.count);
                       向input core报告
                        input_report_abs(ts.input, ABS_X, ts.xp);
                        input_report_abs(ts.input, ABS_Y, ts.yp);

                        input_report_key(ts.input, BTN_TOUCH, 1);
                        input_sync(ts.input);

                        ts.xp = 0;
                        ts.yp = 0;
                        ts.count = 0;
                }
               因为触摸板还是被按着的，继续安排采样
                s3c_adc_start(ts.client, 0, 1 << ts.shift);
        } else {

   down=0是表示触摸板已被释放
                ts.xp = 0;
                ts.yp = 0;
                ts.count = 0;

                input_report_key(ts.input, BTN_TOUCH, 0);
                input_sync(ts.input);

                writel(WAIT4INT | INT_DOWN, ts.io + S3C2410_ADCTSC);
        }
}

初始化一个定时器，toch_timer_fire绑定，在后面会用到
static DEFINE_TIMER(touch_timer, touch_timer_fire, 0, 0);

/**
 * stylus_irq - touchscreen stylus event interrupt
 * @irq: The interrupt number
 * @dev_id: The device ID.
 *
 * Called when the IRQ_TC is fired for a pen up or down event.
 */

       interrupt handler，为input system的中断用
static irqreturn_t stylus_irq(int irq, void *dev_id)
{
        unsigned long data0;
        unsigned long data1;
        bool down;

        data0 = readl(ts.io + S3C2410_ADCDAT0);
        data1 = readl(ts.io + S3C2410_ADCDAT1);

        down = get_down(data0, data1);

        /* TODO we should never get an interrupt with down set while
         * the timer is running, but maybe we ought to verify that the
         * timer isn't running anyways. */

             s3c_adc_start -- 加入adc采样队列，开始采样

              采用的是多次采样的方法，采样次数为2的ts.shift次方
        if (down)
                s3c_adc_start(ts.client, 0, 1 << ts.shift);
        else
                dev_dbg(ts.dev, "%s: count=%d\n", __func__, ts.count);

        if (ts.features & FEAT_PEN_IRQ) {
                /* Clear pen down/up interrupt */
                writel(0x0, ts.io + S3C64XX_ADCCLRINTPNDNUP);
        }

        return IRQ_HANDLED;
}

以下2个函数： s3c24xx_ts_conversion 和 s3c24xx_ts_select是为注册adc要用到的
/**
 * s3c24xx_ts_conversion - ADC conversion callback
 * @client: The client that was registered with the ADC core.
 * @data0: The reading from ADCDAT0.
 * @data1: The reading from ADCDAT1.
 * @left: The number of samples left.
 *
 * Called when a conversion has finished.
 */
static void s3c24xx_ts_conversion(struct s3c_adc_client *client,
                                  unsigned data0, unsigned data1,
                                  unsigned *left)
{
        dev_dbg(ts.dev, "%s: %d,%d\n", __func__, data0, data1);

       驱动采用的是多次采样，然后求平均的方法来获取ADC 转换的数据，因此，每次转换完后先把数据累加起来
        ts.xp += data0;
        ts.yp += data1;

        ts.count++;

        /* From tests, it seems that it is unlikely to get a pen-up
         * event during the conversion process which means we can
         * ignore any pen-up events with less than the requisite
         * count done.
         *
         * In several thousand conversions, no pen-ups where detected
         * before count completed.
         */
}

/**
 * s3c24xx_ts_select - ADC selection callback.
 * @client: The client that was registered with the ADC core.
 * @select: The reason for select.
 *
 * Called when the ADC core selects (or deslects) us as a client.
 */
static void s3c24xx_ts_select(struct s3c_adc_client *client, unsigned select)
{

当select为1时，继续采样；当select为0时，完成采样，并通过定时器调用touch_timer_fire()
        if (select) {
                writel(S3C2410_ADCTSC_PULL_UP_DISABLE | AUTOPST,
                       ts.io + S3C2410_ADCTSC);
        } else {
                mod_timer(&touch_timer, jiffies+1); //通过定时器的方法，jiffies+1实际上是立即安排定时器执行，调用touch_timer_fire 函数
                writel(WAIT4INT | INT_UP, ts.io + S3C2410_ADCTSC);
        }
}

/**
 * s3c2410ts_probe - device core probe entry point
 * @pdev: The device we are being bound to.
 *
 * Initialise, find and allocate any resources we need to run and then
 * register with the ADC and input systems.
 */
static int __devinit s3c2410ts_probe(struct platform_device *pdev)
{
        struct s3c2410_ts_mach_info *info;
        struct device *dev = &pdev->dev;
        struct input_dev *input_dev;
        struct resource *res;
        int ret = -EINVAL;

        /* Initialise input stuff */
        memset(&ts, 0, sizeof(struct s3c2410ts));

        ts.dev = dev;

        info = pdev->dev.platform_data;
        if (!info) {
                dev_err(dev, "no platform data, cannot attach\n");
                return -EINVAL;
        }

        dev_dbg(dev, "initialising touchscreen\n");

        ts.clock = clk_get(dev, "adc");
        if (IS_ERR(ts.clock)) {
                dev_err(dev, "cannot get adc clock source\n");
                return -ENOENT;
        }

        clk_enable(ts.clock);
        dev_dbg(dev, "got and enabled clocks\n");

             platform_get_irq --> platform_get_resource 通过这个调用，从device的struct resource中获得中断源

        ts.irq_tc = ret = platform_get_irq(pdev, 0);
        if (ret < 0) {
                dev_err(dev, "no resource for interrupt\n");
                goto err_clk;
        }

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (!res) {
                dev_err(dev, "no resource for registers\n");
                ret = -ENOENT;
                goto err_clk;
        }

        ts.io = ioremap(res->start, resource_size(res));
        if (ts.io == NULL) {
                dev_err(dev, "cannot map registers\n");
                ret = -ENOMEM;
                goto err_clk;
        }

        /* inititalise the gpio */
        if (info->cfg_gpio)
                info->cfg_gpio(to_platform_device(ts.dev));

        ts.client = s3c_adc_register(pdev, s3c24xx_ts_select,
                                     s3c24xx_ts_conversion, 1);
        if (IS_ERR(ts.client)) {
                dev_err(dev, "failed to register adc client\n");
                ret = PTR_ERR(ts.client);
                goto err_iomap;
        }

        /* Initialise registers */
        if ((info->delay & 0xffff) > 0)
                writel(info->delay & 0xffff, ts.io + S3C2410_ADCDLY);

        writel(WAIT4INT | INT_DOWN, ts.io + S3C2410_ADCTSC);

        input_dev = input_allocate_device();
        if (!input_dev) {
                dev_err(dev, "Unable to allocate the input device !!\n");
                ret = -ENOMEM;
                goto err_iomap;
        }

        ts.input = input_dev;
        ts.input->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
        ts.input->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);
        input_set_abs_params(ts.input, ABS_X, 0, 0x3FF, 0, 0);
        input_set_abs_params(ts.input, ABS_Y, 0, 0x3FF, 0, 0);

        ts.input->name = "S3C24XX TouchScreen";
        ts.input->id.bustype = BUS_HOST;
        ts.input->id.vendor = 0xDEAD;
        ts.input->id.product = 0xBEEF;
        ts.input->id.version = 0x0102;

        ts.shift = info->oversampling_shift;
        ts.features = platform_get_device_id(pdev)->driver_data;

        ret = request_irq(ts.irq_tc, stylus_irq, IRQF_DISABLED,
                          "s3c2410_ts_pen", ts.input);
        if (ret) {
                dev_err(dev, "cannot get TC interrupt\n");
                goto err_inputdev;
        }

        dev_info(dev, "driver attached, registering input device\n");

        /* All went ok, so register to the input system */
        ret = input_register_device(ts.input);
        if (ret < 0) {
                dev_err(dev, "failed to register input device\n");
                ret = -EIO;
                goto err_tcirq;
        }

        return 0;

 err_tcirq:
        free_irq(ts.irq_tc, ts.input);
 err_inputdev:
        input_unregister_device(ts.input);
 err_iomap:
        iounmap(ts.io);
 err_clk:
        del_timer_sync(&touch_timer);
        clk_put(ts.clock);
        return ret;
}

/**
 * s3c2410ts_remove - device core removal entry point
 * @pdev: The device we are being removed from.
 *
 * Free up our state ready to be removed.
 */
static int __devexit s3c2410ts_remove(struct platform_device *pdev)
{
        free_irq(ts.irq_tc, ts.input);
        del_timer_sync(&touch_timer);

        clk_disable(ts.clock);
        clk_put(ts.clock);

        input_unregister_device(ts.input);
        iounmap(ts.io);

        return 0;
}

#ifdef CONFIG_PM
static int s3c2410ts_suspend(struct device *dev)
{
        writel(TSC_SLEEP, ts.io + S3C2410_ADCTSC);
        disable_irq(ts.irq_tc);
        clk_disable(ts.clock);

        return 0;
}

static int s3c2410ts_resume(struct device *dev)
{
        struct platform_device *pdev = to_platform_device(dev);
        struct s3c2410_ts_mach_info *info = pdev->dev.platform_data;

        clk_enable(ts.clock);
        enable_irq(ts.irq_tc);

        /* Initialise registers */
        if ((info->delay & 0xffff) > 0)
                writel(info->delay & 0xffff, ts.io + S3C2410_ADCDLY);

        writel(WAIT4INT | INT_DOWN, ts.io + S3C2410_ADCTSC);

        return 0;
}

static struct dev_pm_ops s3c_ts_pmops = {
        .suspend        = s3c2410ts_suspend,
        .resume         = s3c2410ts_resume,
};
#endif

static struct platform_device_id s3cts_driver_ids[] = {
        { "s3c2410-ts", 0 },
        { "s3c2440-ts", 0 },
        { "s3c64xx-ts", FEAT_PEN_IRQ },
        { }
};
MODULE_DEVICE_TABLE(platform, s3cts_driver_ids);

static struct platform_driver s3c_ts_driver = {
        .driver         = {
                .name   = "samsung-ts",
                .owner  = THIS_MODULE,
#ifdef CONFIG_PM
                .pm     = &s3c_ts_pmops,
#endif
        },
        .id_table       = s3cts_driver_ids,
        .probe          = s3c2410ts_probe,
        .remove         = __devexit_p(s3c2410ts_remove),
};

static int __init s3c2410ts_init(void)
{
        return platform_driver_register(&s3c_ts_driver);
}

static void __exit s3c2410ts_exit(void)
{
        platform_driver_unregister(&s3c_ts_driver);
}

module_init(s3c2410ts_init);
module_exit(s3c2410ts_exit);

MODULE_AUTHOR("Arnaud Patard <arnaud.patard@rtp-net.org>, "
              "Ben Dooks <ben@simtec.co.uk>, "
              "Simtec Electronics <linux@simtec.co.uk>");
MODULE_DESCRIPTION("S3C24XX Touchscreen driver");
MODULE_LICENSE("GPL v2");