S3C6410开发板linux下触摸屏驱动分析
一般LCD的背光是通过PWM的占空比来设置。这里使用的所谓的“一线触屏”方式。原理是板子和触屏模块之间使用一个IO口连接，触屏模块有单片机，通过协议，发送和接收一段频率固定的脉冲数据。本例中IO口使用的GPF［15］（PWM脚，但求使用该功能，仅作为IO使用）。
驱动中有两个定时器，一个是一直打开的定时器one_wire_timer（它是linux内核定时器）,它的间隔是20ms，在每个时隔后先判断是否发送背光控制命令，如果没有背光命令，则发送获取LCD信息命令REQ_INFO或发送获取触屏状态命令REQ_TS。
驱动中有两个定时器，一个是一直打开的定时器one_wire_timer（它是linux内核定时器）,它的间隔是20ms，在每个时隔后先判断是否发送背光控制命令，如果没有背光命令，则发送获取LCD信息命令REQ_INFO或发送获取触屏状态命令REQ_TS。
每个命令的执行过程是一个状态机，状态机的执行节拍是由定时器（它是硬件定时器），它在命令执行开始时打开，并在命令执行完成后关闭。
/* * mini6410_1wire_host.c * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * LCD-CPU one wire communication for Mini6410 from * FriendlyARM Guangzhou CO., LTD. * * Copyright (c) 2010 FriendlyARM Guangzhou CO., LTD. <http://www.arm9.net> * * ChangeLog * * * 2010-10-14: Russell Guo <[email protected]> * - Initial version * -- request touch-screen data * -- request LCD type, Firmware version * - Backlight control * * the CRC-8 functions is based on web page from http://lfh1986.blogspot.com */ #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/clk.h> #include <linux/miscdevice.h> #include <linux/timer.h> #include <linux/param.h> #include <linux/poll.h> #include <linux/proc_fs.h> #include <asm/io.h> #include <asm/irq.h> #include <asm/uaccess.h> #include <plat/regs-timer.h> #include <plat/gpio-cfg.h> #include <plat/regs-clock.h> #include <plat/regs-gpio.h> #include <plat/gpio-bank-e.h> #include <plat/gpio-bank-f.h> #include <linux/cdev.h> #include <linux/sched.h> #include <linux/interrupt.h> #include <linux/irq.h> #include <linux/err.h> #include <linux/io.h> #include <asm/system.h> #include <asm/leds.h> #include <asm/mach-types.h> #include <asm/irq.h> #include <mach/map.h> #include <mach/regs-irq.h> #include <asm/mach/time.h> #include <plat/clock.h> #include <plat/cpu.h> #undef DEBUG #define DEBUG #ifdef DEBUG #define DPRINTK(x...) {printk("%s(%d): ",__FUNCTION__ ,__LINE__);printk(x);} #else #define DPRINTK(x...) (void)(0) #endif #define TOUCH_DEVICE_NAME "touchscreen-1wire" #define BACKLIGHT_DEVICE_NAME "backlight-1wire" #define SAMPLE_BPS 9600 #define SLOW_LOOP_FEQ 25 #define FAST_LOOP_FEQ 60 #define REQ_TS 0x40U #define REQ_INFO 0x60U // Touch Screen driver interface // static DECLARE_WAIT_QUEUE_HEAD(ts_waitq); static int ts_ready; static unsigned ts_status; //当接收到触屏信息后调用此函数，x,y是坐标，down表示是否被按下 static inline void notify_ts_data(unsigned x, unsigned y, unsigned down) { if (!down && !(ts_status &(1U << 31))) {//如果上一次已经按下，现在抬起，不会进if。如果上一次和现在都是未按下，则进if。 // up repeat, give it up return; } ts_status = ((x << 16) | (y)) | (down << 31); //ts_status记录的是触屏信息 ts_ready = 1; wake_up_interruptible(&ts_waitq); } //触屏状态信息的读取（阻塞方式），仅当屏按下时或上一次按下现在未按下，才会成功读取ts_status static ssize_t ts_read(struct file *filp, char *buffer, size_t count, loff_t *ppos) { unsigned long err; if (!ts_ready) { if (filp->f_flags & O_NONBLOCK) return -EAGAIN; else wait_event_interruptible(ts_waitq, ts_ready); } ts_ready = 0; if (count < sizeof ts_status) { return -EINVAL; } else { count = sizeof ts_status; } err = copy_to_user((void *)buffer, (const void *)(&ts_status), sizeof ts_status); return err ? -EFAULT : sizeof ts_status; } //查询是否获取到触屏状态信息 static unsigned int ts_poll( struct file *file, struct poll_table_struct *wait) { unsigned int mask = 0; poll_wait(file, &ts_waitq, wait); if (ts_ready) mask |= POLLIN | POLLRDNORM; return mask; } static struct file_operations ts_fops = { owner: THIS_MODULE, read: ts_read, poll: ts_poll, }; static struct miscdevice ts_misc = { .minor = 181, .name = TOUCH_DEVICE_NAME, .fops = &ts_fops, }; static DECLARE_WAIT_QUEUE_HEAD(bl_waitq); static int bl_ready; static unsigned char backlight_req = 0; //当应用层通过write方法发送一个设置背光指示时，此值变为1.它通知状态机下一个状态执行设置背光命令。 static unsigned char backlight_init_success; //当linux启动时, 它的值为0，这个驱动一加载就会发送设置背光命令给触屏模块，设置完成后此变量的值变为1，此后就不变有作用。 //发送设置背光命令后，当状态机结束时调用此函数。在状态机的结束时会接收数据（参数a,b,c），这些数据不使用。 static inline void notify_bl_data(unsigned char a, unsigned char b, unsigned char c) { bl_ready = 1; backlight_init_success = 1; wake_up_interruptible(&bl_waitq); } //应用层通过写入用字符表示的亮度作为参数，如echo 127 > /dev/backlight-1wire //backlight_req是亮度参数 static ssize_t bl_write(struct file *file, const char *buffer, size_t count, loff_t * ppos) { int ret; char buf[4] = {0, 0, 0, 0}; unsigned v; unsigned len; if (count == 0) { return -EINVAL; } if (count > sizeof buf - 1) { len = sizeof buf - 1; } else { len = count; } ret = copy_from_user(buf, buffer, len); if (ret) { return -EFAULT; } if (sscanf(buf, "%u", &v) != 1) { return -EINVAL; } if (v > 127) { v = 127; } bl_ready = 0; backlight_req = v + 0x80U; //亮度 ret = wait_event_interruptible_timeout(bl_waitq, bl_ready, HZ / 10); if (ret < 0) { return ret; } if (ret == 0) { return -ETIMEDOUT; } return count; } static struct file_operations bl_fops = { owner: THIS_MODULE, write: bl_write, }; static struct miscdevice bl_misc = { .minor = MISC_DYNAMIC_MINOR, .name = BACKLIGHT_DEVICE_NAME, .fops = &bl_fops, }; // for query base info //LCD的信息，通过发送获取LCD信息命令（REQ_INFO）可得到这两个变量的值。 static unsigned lcd_type, firmware_ver; //在获取LCD信息命令的结束将调用此函数 static inline void notify_info_data(unsigned char _lcd_type, unsigned char ver_year, unsigned char week) { if (_lcd_type != 0xFF) { lcd_type = _lcd_type; firmware_ver = ver_year * 100 + week; } } // Pin access //以下几个函数设置IO口 static inline void set_pin_up(void) { unsigned long tmp; tmp = readl(S3C64XX_GPFPUD); tmp &= ~(3U <<30); tmp |= (2U << 30); writel(tmp, S3C64XX_GPFPUD); } static inline void set_pin_as_input(void) { unsigned long tmp; tmp = readl(S3C64XX_GPFCON); tmp &= ~(3 << 30); writel(tmp, S3C64XX_GPFCON); } static inline void set_pin_as_output(void) { unsigned long tmp; tmp = readl(S3C64XX_GPFCON); tmp = (tmp & ~(3U << 30)) | (1U << 30); writel(tmp, S3C64XX_GPFCON); } static inline void set_pin_value(int v) { unsigned long tmp; tmp = readl(S3C64XX_GPFDAT); if (v) { tmp |= (1 << 15); } else { tmp &= ~(1<<15); } writel(tmp, S3C64XX_GPFDAT); } static inline int get_pin_value(void) { int v; unsigned long tmp; tmp = readl(S3C64XX_GPFDAT); v = !!(tmp & (1<<15)); return v; } // CRC // 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)]) // once a session complete static unsigned total_received, total_error; static unsigned last_req, last_res; //当状态机接收到数据后执行此函数 static void one_wire_session_complete(unsigned char req, unsigned int res) { unsigned char crc; const unsigned char *p = (const unsigned char*)&res; total_received ++; last_res = res; crc8_init(crc); crc8(crc, p[3]); crc8(crc, p[2]); crc8(crc, p[1]); if (crc != p[0]) { //判断接收数据的CRC是否正确 // CRC dismatch if (total_received > 100) { total_error++; } return; } switch(req) { case REQ_TS: //得到触屏的状态 { unsigned short x,y; //触屏的坐标 unsigned pressed; //是否按下 x = ((p[3] >> 4U) << 8U) + p[2]; y = ((p[3] & 0xFU) << 8U) + p[1]; pressed = (x != 0xFFFU) && (y != 0xFFFU); notify_ts_data(x, y, pressed); } break; case REQ_INFO: // 得到lcd信息 notify_info_data(p[3], p[2], p[1]); break; default: notify_bl_data(p[3], p[2], p[1]); // 设置背光完成 break; } } // one-wire protocol core static unsigned long TCNT_FOR_SAMPLE_BIT; static unsigned long TCNT_FOR_FAST_LOOP; static unsigned long TCNT_FOR_SLOW_LOOP; static int init_timer_for_1wire(void) { unsigned long tcfg1; unsigned long tcfg0; unsigned prescale1_value; unsigned long pclk; struct clk *clk; // get pclk clk = clk_get(NULL, "timers"); if (IS_ERR(clk)) { DPRINTK("ERROR to get PCLK\n"); return -EIO; } pclk = clk_get_rate(clk); // get prescaler tcfg0 = __raw_readl(S3C2410_TCFG0); // we use system prescaler value because timer 4 uses same one prescale1_value = (tcfg0 >> 8) & 0xFF; // calc the TCNT_FOR_SAMPLE_BIT, that is one of the goal TCNT_FOR_SAMPLE_BIT = pclk / (prescale1_value + 1) / SAMPLE_BPS - 1; TCNT_FOR_FAST_LOOP = pclk / (prescale1_value + 1) / FAST_LOOP_FEQ - 1; TCNT_FOR_SLOW_LOOP = pclk / (prescale1_value + 1) / SLOW_LOOP_FEQ - 1; // select timer 3, the 2rd goal tcfg1 = __raw_readl(S3C2410_TCFG1); tcfg1 &= ~S3C2410_TCFG1_MUX3_MASK; writel(tcfg1, S3C2410_TCFG1); return 0; } static inline void stop_timer_for_1wire(void) { unsigned long tcon; tcon = __raw_readl(S3C2410_TCON); tcon &= ~S3C2410_TCON_T3START; writel(tcon, S3C2410_TCON); } //状态机的状态，工作的起始态是START. enum { IDLE, START, REQUEST, WAITING, RESPONSE, STOPING, } one_wire_status = IDLE; static volatile unsigned int io_bit_count; static volatile unsigned int io_data; static volatile unsigned char one_wire_request; static irqreturn_t timer_for_1wire_interrupt(int irq, void *dev_id) { io_bit_count--; //起计时作用 switch(one_wire_status) { case START: //start_one_wire_session已经指定io_bit_count = 1 if (io_bit_count == 0) { //这个状态的计时结束 io_bit_count = 16; //设置下一个状态的时间总数 one_wire_status = REQUEST; } break; //REQUEST是一个发送命令类型的过程，发送的数据是16位。 case REQUEST: //io_bit_count = 16 // Send a bit 发送的是io_data的高16位。高16位由高8位的req和低8位crc组成。 set_pin_value(io_data & (1U << 31)); io_data <<= 1; if (io_bit_count == 0) { io_bit_count = 2; one_wire_status = WAITING; } break; //等待 case WAITING: // 2 if (io_bit_count == 0) { io_bit_count = 32; one_wire_status = RESPONSE; } if (io_bit_count == 1) { set_pin_as_input(); set_pin_value(1); } break; //此状态接收32位数据 case RESPONSE: // 32 // Get a bit 读出32位数 io_data = (io_data << 1) | get_pin_value(); if (io_bit_count == 0) { io_bit_count = 2; one_wire_status = STOPING; set_pin_value(1); set_pin_as_output(); one_wire_session_complete(one_wire_request, io_data); } break; case STOPING: // 2 if (io_bit_count == 0) { one_wire_status = IDLE; stop_timer_for_1wire(); } break; default: stop_timer_for_1wire(); } return IRQ_HANDLED; } static struct irqaction timer_for_1wire_irq = { //状态机时钟节拍的定时器，使用硬件Timer .name = "1-wire Timer Tick", .flags = IRQF_DISABLED | IRQF_IRQPOLL, .handler = timer_for_1wire_interrupt, .dev_id = &timer_for_1wire_irq, }; //初始化，仅在状态开始调用一次 static void start_one_wire_session(unsigned char req) { unsigned long tcon; unsigned long flags; if (one_wire_status != IDLE) { printk("one_wire_status: %d\n", one_wire_status); return; } one_wire_status = START; //初始状态，开始一个状态 set_pin_value(1); set_pin_as_output(); // IDLE to START { unsigned char crc; crc8_init(crc); crc8(crc, req); io_data = (req << 8) + crc; io_data <<= 16; } last_req = (io_data >> 16); one_wire_request = req; io_bit_count = 1; set_pin_as_output(); //打开timer writel(TCNT_FOR_SAMPLE_BIT, S3C2410_TCNTB(3)); // init tranfer and start timer tcon = __raw_readl(S3C2410_TCON); tcon &= ~(0xF << 16); tcon |= S3C2410_TCON_T3MANUALUPD; writel(tcon, S3C2410_TCON); tcon |= S3C2410_TCON_T3START; tcon |= S3C2410_TCON_T3RELOAD; tcon &= ~S3C2410_TCON_T3MANUALUPD; local_irq_save(flags); writel(tcon, S3C2410_TCON); set_pin_value(0); local_irq_restore(flags); } // poll the device // following is Linux timer not HW timer static int exitting; static struct timer_list one_wire_timer; void one_wire_timer_proc(unsigned long v) //每20ms调用一次，它或者执行设置背光亮度或者获取触摸数据 { unsigned char req; if (exitting) { return; } one_wire_timer.expires = jiffies + HZ / 50; //20ms add_timer(&one_wire_timer); if (lcd_type == 0) { req = REQ_INFO; } else if (!backlight_init_success) {//如果应用层一次都没有过设置亮度，亮度默认127 req = 127; } else if (backlight_req) { //将要设置亮度 req = backlight_req; backlight_req = 0; } else { req = REQ_TS; //获取触摸数据 } start_one_wire_session(req); } static struct timer_list one_wire_timer = { //这个定时器一直是开着的，每个20ms执行一次 .function = one_wire_timer_proc, }; //通过proc文件系统读取统计信息 static int read_proc(char *buf, char **start, off_t offset, int count, int *eof, void *data) { int len; len = sprintf(buf, "%u %u %u %u %04X %08X\n", lcd_type, firmware_ver, total_received, total_error, last_req, last_res); *eof = 1; return len; } static int __init dev_init(void) { int ret; ret = misc_register(&ts_misc) | misc_register(&bl_misc) ; //set PWM as output, set output is 1. set_pin_up(); set_pin_value(1); set_pin_as_output(); if (ret == 0) { setup_irq(IRQ_TIMER3, &timer_for_1wire_irq); ret = init_timer_for_1wire(); init_timer(&one_wire_timer); one_wire_timer_proc(0); //设置背光为127 (默认) create_proc_read_entry("driver/one-wire-info", 0, NULL, read_proc, NULL); //建立接口到proc文件系统 } if (ret == 0) { printk (TOUCH_DEVICE_NAME"\tinitialized\n"); printk (BACKLIGHT_DEVICE_NAME"\tinitialized\n"); } return ret; } static void __exit dev_exit(void) { exitting = 1; remove_proc_entry("driver/one-wire-info", NULL); del_timer_sync(&one_wire_timer); free_irq(IRQ_TIMER3, &timer_for_1wire_irq); misc_deregister(&ts_misc); misc_deregister(&bl_misc); } module_init(dev_init); module_exit(dev_exit); MODULE_LICENSE("GPL"); MODULE_AUTHOR("FriendlyARM Inc."); MODULE_DESCRIPTION("Mini6410 one-wire host and Touch Screen Driver");