关于mini2440触摸屏驱动中信号量作用的最新解释
这几天仔细分析了下触摸屏驱动程序，对触摸屏驱动程序stylus_action函数中的mod_timer()不是很理解，于是在触摸屏驱动程序中加上了debug信息，进行了测试。添加debug信息后的去驱动代码如下：
/*************************************
NAME:gt2440.c
COPYRIGHT:www.e-online.cc
*************************************/
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/input.h>
#include <linux/init.h>
#include <linux/serio.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/clk.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <plat/regs-adc.h>
#include <mach/regs-gpio.h>
/* For ts.dev.id.version */
#define TSDEBUG
#ifdef TSDEBUG
#define TPDEBUG(fmt,args...) printk("gt2440 ts:" fmt,##args)
#else
#define TPDEBUG(fmt,args...)
#endif
#define S3C2410TSVERSION 0x0101
#define WAIT4INT(x) (((x)<<8) | \
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))
static char *gt2440ts_name = "GT2440 TouchScreen";
static struct input_dev *dev;
static long xp;
static long yp;
static int count;
extern struct semaphore ADC_LOCK;
static int OwnADC = 0;
static void __iomem *base_addr;
static inline void gt2440_ts_connect(void)
{
s3c2410_gpio_cfgpin(S3C2410_GPG12, S3C2410_GPG12_XMON);
s3c2410_gpio_cfgpin(S3C2410_GPG13, S3C2410_GPG13_nXPON);
s3c2410_gpio_cfgpin(S3C2410_GPG14, S3C2410_GPG14_YMON);
s3c2410_gpio_cfgpin(S3C2410_GPG15, S3C2410_GPG15_nYPON);
}
static void touch_timer_fire(unsigned long data)
{
unsigned long data0;
unsigned long data1;
int updown;
data0 = ioread32(base_addr+S3C2410_ADCDAT0);
data1 = ioread32(base_addr+S3C2410_ADCDAT1);
updown = (!(data0 & S3C2410_ADCDAT0_UPDOWN)) && (!(data1 & S3C2410_ADCDAT0_UPDOWN));
if (updown) {
if (count != 0)
{
xp >>= 2;
yp >>= 2;
input_report_abs(dev, ABS_X, xp);
input_report_abs(dev, ABS_Y, yp);
input_report_key(dev, BTN_TOUCH, 1);
input_report_abs(dev, ABS_PRESSURE, 1);
input_sync(dev);
TPDEBUG("touch_timer_fire func report key:%d,%d\n",xp,yp);
}
xp = 0;
yp = 0;
count = 0;
iowrite32(S3C2410_ADCTSC_PULL_UP_DISABLE | AUTOPST, base_addr+S3C2410_ADCTSC);
iowrite32(ioread32(base_addr+S3C2410_ADCCON) | S3C2410_ADCCON_ENABLE_START, base_addr+S3C2410_ADCCON);
TPDEBUG("touch_timer_fire func start ADC\n");
}
else
{
count = 0;
input_report_key(dev, BTN_TOUCH, 0);
input_report_abs(dev, ABS_PRESSURE, 0);
input_sync(dev);
iowrite32(WAIT4INT(0), base_addr+S3C2410_ADCTSC);
if (OwnADC)
{
OwnADC = 0;
up(&ADC_LOCK);
}
TPDEBUG("touch_timer_fire func stylus up\n");
}
}
static struct timer_list touch_timer =
TIMER_INITIALIZER(touch_timer_fire, 0, 0);
static irqreturn_t stylus_updown(int irq, void *dev_id)
{
unsigned long data0;
unsigned long data1;
int updown;
TPDEBUG("stylus_updown func init\n");
if (down_trylock(&ADC_LOCK) == 0)
{
OwnADC = 1;
data0 = ioread32(base_addr+S3C2410_ADCDAT0);
data1 = ioread32(base_addr+S3C2410_ADCDAT1);
updown = (!(data0 & S3C2410_ADCDAT0_UPDOWN)) && (!(data1 & S3C2410_ADCDAT0_UPDOWN));
if (updown)
{
TPDEBUG("stylus_updown func:stylus down\n");
touch_timer_fire(0);
}
else
{
TPDEBUG("stylus_updown func:stylus up\n");
OwnADC = 0;
up(&ADC_LOCK);
}
}
return IRQ_HANDLED;
}
static irqreturn_t stylus_action(int irq, void *dev_id)
{
unsigned long data0;
unsigned long data1;
if (OwnADC)
{
data0 = ioread32(base_addr+S3C2410_ADCDAT0);
data1 = ioread32(base_addr+S3C2410_ADCDAT1);
xp += data0 & S3C2410_ADCDAT0_XPDATA_MASK;
yp += data1 & S3C2410_ADCDAT1_YPDATA_MASK;
count++;
if (count < (1<<4))
{
iowrite32(S3C2410_ADCTSC_PULL_UP_DISABLE | AUTOPST, base_addr+S3C2410_ADCTSC);
iowrite32(ioread32(base_addr+S3C2410_ADCCON) | S3C2410_ADCCON_ENABLE_START, base_addr+S3C2410_ADCCON);
TPDEBUG("stylus_action func still adc\n");
}
else
{
TPDEBUG("stylus_action func report key\n");
mod_timer(&touch_timer, jiffies+1);
iowrite32(WAIT4INT(1), base_addr+S3C2410_ADCTSC);
TPDEBUG("stylus_action func wait interrupt\n");
}
}
return IRQ_HANDLED;
}
static struct clk *adc_clock;
static int __init gt2440ts_init(void)
{
struct input_dev *input_dev;
adc_clock = clk_get(NULL, "adc");
if (!adc_clock)
{
printk(KERN_ERR "failed to get adc clock source\n");
return -ENOENT;
}
clk_enable(adc_clock);
base_addr=ioremap(S3C2410_PA_ADC,0x20);
if (base_addr == NULL)
{
printk(KERN_ERR "Failed to remap register block\n");
return -ENOMEM;
}
/* Configure GPIOs */
//gt2440_ts_connect();
iowrite32(S3C2410_ADCCON_PRSCEN | S3C2410_ADCCON_PRSCVL(100),base_addr+S3C2410_ADCCON);
iowrite32(0x4fff, base_addr+S3C2410_ADCDLY);
iowrite32(WAIT4INT(0), base_addr+S3C2410_ADCTSC);
/* Initialise input stuff */
input_dev = input_allocate_device();
if (!input_dev)
{
printk(KERN_ERR "Unable to allocate the input device !!\n");
return -ENOMEM;
}
dev = input_dev;
dev->evbit[0] = BIT(EV_SYN) | BIT(EV_KEY) | BIT(EV_ABS);
dev->keybit[BITS_TO_LONGS(BTN_TOUCH)] = BIT(BTN_TOUCH);
input_set_abs_params(dev, ABS_X, 0, 0x3FF, 0, 0);
input_set_abs_params(dev, ABS_Y, 0, 0x3FF, 0, 0);
input_set_abs_params(dev, ABS_PRESSURE, 0, 1, 0, 0);
dev->name = gt2440ts_name;
dev->id.bustype = BUS_RS232;
dev->id.vendor = 0xDEAD;
dev->id.product = 0xBEEF;
dev->id.version = S3C2410TSVERSION;
if (request_irq(IRQ_ADC, stylus_action, IRQF_SHARED|IRQF_SAMPLE_RANDOM, gt2440ts_name, dev))
{
printk(KERN_ERR "gt2440_ts.c: Could not allocate ts IRQ_ADC !\n");
iounmap(base_addr);
return -EIO;
}
if (request_irq(IRQ_TC, stylus_updown, IRQF_SAMPLE_RANDOM, gt2440ts_name, dev))
{
printk(KERN_ERR "gt2440_ts.c: Could not allocate ts IRQ_ADC !\n");
iounmap(base_addr);
return -EIO;
}
printk(KERN_INFO "%s successfully loaded\n", gt2440ts_name);
input_register_device(dev);
return 0;
}
static void __exit gt2440ts_exit(void)
{
disable_irq(IRQ_ADC);
disable_irq(IRQ_TC);
free_irq(IRQ_TC,dev);
free_irq(IRQ_ADC,dev);
if (adc_clock)
{
clk_disable(adc_clock);
clk_put(adc_clock);
adc_clock = NULL;
}
input_unregister_device(dev);
iounmap(base_addr);
}
module_init(gt2440ts_init);
module_exit(gt2440ts_exit);
驱动程序测试结果输入：
gt2440 ts: stylus_updown func init gt2440 ts: stylus_updown func:stylus down gt2440 ts: touch_timer_fire func start ADC gt2440 ts: stylus_action func still adc gt2440 ts: stylus_action func still adc gt2440 ts: stylus_action func still adc gt2440 ts: stylus_action func still adc gt2440 ts: stylus_action func still adc gt2440 ts: stylus_action func still adc gt2440 ts: stylus_action func still adc gt2440 ts: stylus_action func still adc gt2440 ts: stylus_action func still adc gt2440 ts: stylus_action func still adc gt2440 ts: stylus_action func still adc gt2440 ts: stylus_action func still adc gt2440 ts: stylus_action func still adc gt2440 ts: stylus_action func still adc gt2440 ts: stylus_action func still adc gt2440 ts: stylus_action func report key gt2440 ts: stylus_action func wait interrupt gt2440 ts: stylus_updown func ini gt2440 ts: touch_timer_fire func report key 676,,4347
根据后面的三条输出结果我们在分析一遍程序stylus_updown()->touch_timer_fire()->stylus_action()->stylus_updown()->touch_timer_fire(),因此，stylus_updown函数中的if (down_trylock(&ADC_LOCK) == 0)不仅仅是保证任何时候都只有一个驱动程序使用ADC，同时还有一个重要作用就是保证当触摸屏一直被按下时，不重复进入终端触发定时器函数。