imx6uart分析本⽂主要记录： 1、uart设备注册 2、uart驱动注册 3、上层应⽤调⽤有些地⽅理解的还不是很透彻，希望指正。
1、uart设备注册过程MACHINE_START(MX6Q_SABRESD, "Freescale i.MX 6Quad/DualLite/Solo Sabre-SD Board")/* Maintainer: Freescale Semiconductor, Inc. */.boot_params = MX6_PHYS_OFFSET + 0x100,.fixup = fixup_mxc_board,.map_io = mx6_map_io,.init_irq = mx6_init_irq,.init_machine = mx6_sabresd_board_init, ------------------------+.timer = &mx6_sabresd_timer, |.reserve = mx6q_sabresd_reserve, |MACHINE_END ||static void __init mx6_sabresd_board_init(void) <-----------------------+{int i;int ret;struct clk *clko, *clko2;struct clk *new_parent;int rate;if (cpu_is_mx6q())mxc_iomux_v3_setup_multiple_pads(mx6q_sabresd_pads, ----+ARRAY_SIZE(mx6q_sabresd_pads)); |else if (cpu_is_mx6dl()) { |mxc_iomux_v3_setup_multiple_pads(mx6dl_sabresd_pads, |ARRAY_SIZE(mx6dl_sabresd_pads)); |} |... ... |mx6q_sabresd_init_uart(); ------------------------|----+... ... | |} | |//设置IOMUX寄存器，将有功能复⽤的引脚设置为UART功能 | |static iomux_v3_cfg_t mx6q_sabresd_pads[] = { <---------------+ |... ... |/* UART1 for debug */ |MX6Q_PAD_CSI0_DAT10__UART1_TXD, |MX6Q_PAD_CSI0_DAT11__UART1_RXD, ||/* UART2*/ |MX6Q_PAD_EIM_D26__UART2_TXD, |MX6Q_PAD_EIM_D27__UART2_RXD, ||/* UART3 for gps */ |MX6Q_PAD_EIM_D24__UART3_TXD, |MX6Q_PAD_EIM_D25__UART3_RXD, ||/* UART4*/ |MX6Q_PAD_KEY_COL0__UART4_TXD, |MX6Q_PAD_KEY_ROW0__UART4_RXD, ||/* UART5*/ |MX6Q_PAD_KEY_COL1__UART5_TXD, |MX6Q_PAD_KEY_ROW1__UART5_RXD, |... ... |}; ||//uart初始化 |static inline void mx6q_sabresd_init_uart(void) <----------------+{imx6q_add_imx_uart(0, NULL);imx6q_add_imx_uart(1, NULL);imx6q_add_imx_uart(2, NULL);imx6q_add_imx_uart(3, NULL);imx6q_add_imx_uart(4, NULL);}#define imx6q_add_imx_uart(id, pdata) \imx_add_imx_uart_1irq(&imx6q_imx_uart_data[id], pdata)const struct imxuart_platform_data *pdata){struct resource res[] = {{.start = data->iobase,.end = data->iobase + data->iosize - 1,.flags = IORESOURCE_MEM,}, {.start = data->irq,.end = data->irq,.flags = IORESOURCE_IRQ,},};return imx_add_platform_device("imx-uart", data->id, res, ARRAY_SIZE(res), pdata, sizeof(*pdata)); |} ||Vstatic inline struct platform_device *imx_add_platform_device( const char *name, int id,const struct resource *res, unsigned int num_resources,const void *data, size_t size_data){return imx_add_platform_device_dmamask(name, id, res, num_resources, data, size_data, 0);}2、驱动注册kernel/drivers/tty/serial/imx.cstatic int __init imx_serial_init(void){int ret;printk(KERN_INFO "Serial: IMX driver\n");ret = uart_register_driver(&imx_reg); ----------------------------+if (ret) | |return ret; +----------------------------+ |//注册uart驱动 | |ret = platform_driver_register(&serial_imx_driver); | |if (ret != 0) | | |uart_unregister_driver(&imx_reg); | | |+--------------|-------|----+return0; | | |} | | || | |static struct uart_driver imx_reg = { <----------------------+ | |.owner = THIS_MODULE, | |.driver_name = DRIVER_NAME, // IMX-uart | |.dev_name = DEV_NAME, // ttymxc | |.major = SERIAL_IMX_MAJOR, // 207 | |.minor = MINOR_START, // 16 | |.nr = ARRAY_SIZE(imx_ports), | |.cons = IMX_CONSOLE, | |}; | || |// kernel/drivers/tty/serial/serial_core.c | |int uart_register_driver(struct uart_driver *drv) <----------+ |{ |struct tty_driver *normal; |int i, retval; ||BUG_ON(drv->state); |//分配uart_state空间，⼀个串⼝对应⼀个 |/* |* Maybe we should be using a slab cache for this, especially if |* we have a large number of ports to handle. |*/ |drv->state = kzalloc(sizeof(struct uart_state) * drv->nr, GFP_KERNEL); |if (!drv->state) |goto out; |//所有的串⼝只有⼀个tty_driver |normal = alloc_tty_driver(drv->nr); |if (!normal) |goto out_kfree; ||drv->tty_driver = normal; ||normal->owner = drv->owner; |normal->driver_name = drv->driver_name; |normal->type = TTY_DRIVER_TYPE_SERIAL; |normal->subtype = SERIAL_TYPE_NORMAL; |normal->init_termios = tty_std_termios; |normal->init_termios.c_cflag = B9600 | CS8 | CREAD | HUPCL | CLOCAL; |normal->init_termios.c_ispeed = normal->init_termios.c_ospeed = 9600; |normal->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV; | /* tty_driver和uart_driver结构体关联， |* 当驱动和设备匹配之后，调⽤probe函数， |* |*/ |normal->driver_state = drv; |tty_set_operations(normal, &uart_ops); ||/* |* Initialise the UART state(s). |*/ |for (i = 0; i < drv->nr; i++) { |struct uart_state *state = drv->state + i; |struct tty_port *port = &state->port; ||tty_port_init(port); |port->ops = &uart_port_ops; |port->close_delay = 500; /* .5 seconds */ |port->closing_wait = 30000; /* 30 seconds */ |tasklet_init(&state->tlet, uart_tasklet_action, |(unsigned long)state); |} ||retval = tty_register_driver(normal); ------------------------+ |if (retval >= 0) | |return retval; | || |put_tty_driver(normal); | |out_kfree: | |kfree(drv->state); | |out: | |return -ENOMEM; | |} | |// kernel/drivers/tty/tty_io.c | |int tty_register_driver(struct tty_driver *driver) <-------------------+ |{ |int error; |int i; |dev_t dev; |void **p = NULL; |struct device *d; ||if (!(driver->flags & TTY_DRIVER_DEVPTS_MEM) && driver->num) { |p = kzalloc(driver->num * 2 * sizeof(void *), GFP_KERNEL); | if (!p) |return -ENOMEM; |} ||if (!driver->major) { |error = alloc_chrdev_region(&dev, driver->minor_start, |driver->num, driver->name); |if (!error) { |driver->major = MAJOR(dev); |driver->minor_start = MINOR(dev); |} |} else { |dev = MKDEV(driver->major, driver->minor_start); |/* 为设备分配主设备号和次设备号 |* 主设备号207，次设备号从16开始 |* 所以注册的串⼝设备次设备号是16,17,18,19... |*/ |error = register_chrdev_region(dev, driver->num, driver->name); |} |if (error < 0) { |kfree(p); |return error; |} ||if (p) { |driver->ttys = (struct tty_struct **)p; |driver->termios = (struct ktermios **)(p + driver->num); |} else { |driver->ttys = NULL; |driver->termios = NULL; |} ||unregister_chrdev_region(dev, driver->num); |driver->ttys = NULL; |driver->termios = NULL; |kfree(p); |return error; |} ||mutex_lock(&tty_mutex); |list_add(&driver->tty_drivers, &tty_drivers); |mutex_unlock(&tty_mutex); ||if (!(driver->flags & TTY_DRIVER_DYNAMIC_DEV)) { |for (i = 0; i < driver->num; i++) { |d = tty_register_device(driver, i, NULL); |if (IS_ERR(d)) { |error = PTR_ERR(d); |goto err; |} |} |} |proc_tty_register_driver(driver); |driver->flags |= TTY_DRIVER_INSTALLED; |return0; ||err: |for (i--; i >= 0; i--) |tty_unregister_device(driver, i); ||mutex_lock(&tty_mutex); |list_del(&driver->tty_drivers); |mutex_unlock(&tty_mutex); ||unregister_chrdev_region(dev, driver->num); |driver->ttys = NULL; |driver->termios = NULL; |kfree(p); |return error; |} ||static struct platform_driver serial_imx_driver = { <----------------+.probe = serial_imx_probe,.remove = serial_imx_remove,.suspend = serial_imx_suspend,.resume = serial_imx_resume,.driver = {.name = "imx-uart",.owner = THIS_MODULE,},};//当设备和驱动匹配之后，会调⽤probe函数，其中就指定了读写函数static int serial_imx_probe(struct platform_device *pdev){... ...sport->port.ops = &imx_pops; -------+... ... |//将初始化⽤到的uart_driver和imx_port关联起来 |//最终就将操作imx_pops结构体定义的函数与上层应⽤关联起来 | //初始化的时候，就已经将uart_driver与tty_driver关联 |ret = uart_add_one_port(&imx_reg, &sport->port); -------+ |} | || |static struct uart_ops imx_pops = { <-----|----+.tx_empty = imx_tx_empty, |.set_mctrl = imx_set_mctrl, |.get_mctrl = imx_get_mctrl, |.stop_tx = imx_stop_tx, |.start_tx = imx_start_tx, |.stop_rx = imx_stop_rx, |.enable_ms = imx_enable_ms, |.break_ctl = imx_break_ctl, |.startup = imx_startup, |.shutdown = imx_shutdown, |.set_termios = imx_set_termios, |.type = imx_type, |.release_port = imx_release_port, |.request_port = imx_request_port, |.config_port = imx_config_port, |.verify_port = imx_verify_port, |#if defined(CONFIG_CONSOLE_POLL) |Vint uart_add_one_port(struct uart_driver *drv, struct uart_port *uport) {struct uart_state *state;struct tty_port *port;int ret = 0;struct device *tty_dev;BUG_ON(in_interrupt());if (uport->line >= drv->nr)return -EINVAL;state = drv->state + uport->line;port = &state->port;mutex_lock(&port_mutex);mutex_lock(&port->mutex);if (state->uart_port) {ret = -EINVAL;goto out;}state->uart_port = uport;state->pm_state = -1;uport->cons = drv->cons;uport->state = state;/** If this port is a console, then the spinlock is already* initialised.*/if (!(uart_console(uport) && (uport->cons->flags & CON_ENABLED))) { spin_lock_init(&uport->lock);lockdep_set_class(&uport->lock, &port_lock_key);}uart_configure_port(drv, state, uport);/** Register the port whether it's detected or not. This allows* setserial to be used to alter this ports parameters.*/tty_dev = tty_register_device(drv->tty_driver, uport->line, uport->dev);if (likely(!IS_ERR(tty_dev))) {device_set_wakeup_capable(tty_dev, 1);} else {printk(KERN_ERR "Cannot register tty device on line %d\n",uport->line);}/** Ensure UPF_DEAD is not set.*/uport->flags &= ~UPF_DEAD;out:mutex_unlock(&port->mutex);mutex_unlock(&port_mutex);return ret;}3、上层调⽤kernel/drivers/tty/tty_io.cstatic const struct file_operations tty_fops = {.llseek = no_llseek,.read = tty_read,.write = tty_write,.poll = tty_poll,.unlocked_ioctl = tty_ioctl,.compat_ioctl = tty_compat_ioctl,.open = tty_open,.release = tty_release,.fasync = tty_fasync,};// kernel/drivers/tty/tty_io.cstatic ssize_t tty_write(struct file *file, const char __user *buf,struct tty_struct *tty = file_tty(file);struct tty_ldisc *ld;ssize_t ret;if (tty_paranoia_check(tty, inode, "tty_write"))return -EIO;if (!tty || !tty->ops->write ||(test_bit(TTY_IO_ERROR, &tty->flags))) return -EIO;/* Short term debug to catch buggy drivers */if (tty->ops->write_room == NULL)printk(KERN_ERR "tty driver %s lacks a write_room method.\n", tty->driver->name);ld = tty_ldisc_ref_wait(tty);if (!ld->ops->write)ret = -EIO;elseret = do_tty_write(ld->ops->write, tty, file, buf, count);tty_ldisc_deref(ld); |return ret; |} |Vstatic inline ssize_t do_tty_write(ssize_t (*write)(struct tty_struct *, struct file *, const unsigned char *, size_t), struct tty_struct *tty,struct file *file,const char __user *buf,size_t count){ssize_t ret, written = 0;unsigned int chunk;ret = tty_write_lock(tty, file->f_flags & O_NDELAY);if (ret < 0)return ret;chunk = 2048;if (test_bit(TTY_NO_WRITE_SPLIT, &tty->flags))chunk = 65536;if (count < chunk)chunk = count;/* write_buf/write_cnt is protected by the atomic_write_lock mutex */if (tty->write_cnt < chunk) {unsigned char *buf_chunk;if (chunk < 1024)chunk = 1024;buf_chunk = kmalloc(chunk, GFP_KERNEL);if (!buf_chunk) {ret = -ENOMEM;goto out;}kfree(tty->write_buf);tty->write_cnt = chunk;tty->write_buf = buf_chunk;}/* Do the write .. */for (;;) {size_t size = count;if (size > chunk)size = chunk;ret = -EFAULT;if (copy_from_user(tty->write_buf, buf, size))break;ret = write(tty, file, tty->write_buf, size); -----------+if (ret <= 0) |break; |written += ret; |buf += ret; |count -= ret; |if (!count) |break; |ret = -ERESTARTSYS; |if (signal_pending(current)) |break; |cond_resched(); |} |if (written) { |} |out: |tty_write_unlock(tty); |return ret; |} |V//kernel/drivers/tty/n_tty.cstatic ssize_t n_tty_write(struct tty_struct *tty, struct file *file,const unsigned char *buf, size_t nr){const unsigned char *b = buf;DECLARE_WAITQUEUE(wait, current);int c;ssize_t retval = 0;/* Job control check -- must be done at start (POSIX.1 7.1.1.4). */if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {retval = tty_check_change(tty);if (retval)return retval;}/* Write out any echoed characters that are still pending */process_echoes(tty);add_wait_queue(&tty->write_wait, &wait);while (1) {set_current_state(TASK_INTERRUPTIBLE);if (signal_pending(current)) {retval = -ERESTARTSYS;break;}if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {retval = -EIO;break;}if (O_OPOST(tty) && !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {while (nr > 0) {ssize_t num = process_output_block(tty, b, nr);if (num < 0) {if (num == -EAGAIN)break;retval = num;goto break_out;}b += num;nr -= num;if (nr == 0)break;c = *b;if (process_output(c, tty) < 0)break;b++; nr--;}if (tty->ops->flush_chars)tty->ops->flush_chars(tty);} else {while (nr > 0) {c = tty->ops->write(tty, b, nr); -------------------+if (c < 0) { |retval = c; |goto break_out; |} |if (!c) |break; |b += c; |nr -= c; |} |} |if (!nr) |break; |if (file->f_flags & O_NONBLOCK) { |retval = -EAGAIN; |break; |} |schedule(); |} |break_out: |__set_current_state(TASK_RUNNING); |remove_wait_queue(&tty->write_wait, &wait); |if (b - buf != nr && tty->fasync) |// kernel/drivers/tty/serial/imx.c |static void |imx_console_write(struct console *co, const char *s, unsigned int count) <-+ {struct imx_port *sport = imx_ports[co->index];struct imx_port_ucrs old_ucr;unsigned int ucr1;unsigned long flags;int locked = 1;local_irq_save(flags);if (sport->port.sysrq)locked = 0;elsespin_lock(&sport->port.lock);/** First, save UCR1/2/3 and then disable interrupts*/imx_port_ucrs_save(&sport->port, &old_ucr);ucr1 = old_ucr.ucr1;if (cpu_is_mx1())ucr1 |= MX1_UCR1_UARTCLKEN;ucr1 |= UCR1_UARTEN;ucr1 &= ~(UCR1_TXMPTYEN | UCR1_RRDYEN | UCR1_RTSDEN);writel(ucr1, sport->port.membase + UCR1);writel(old_ucr.ucr2 | UCR2_TXEN, sport->port.membase + UCR2);uart_console_write(&sport->port, s, count, imx_console_putchar);/** Finally, wait for transmitter to become empty* and restore UCR1/2/3*/while (!(readl(sport->port.membase + USR2) & USR2_TXDC));imx_port_ucrs_restore(&sport->port, &old_ucr);if (locked)spin_unlock(&sport->port.lock);local_irq_restore(flags);}。
