Linux下串口驱动解析
2023-09-14 08:57:16 时间
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一、核心数据结构
串口驱动有3个核心数据结构,它们都定义在 #include linux/serial_core.h
1、uart_driver uart_driver包含了串口设备名、串口驱动名、主次设备号、串口控制台(可选)等信息,还封装了tty_driver(底层串口驱动无需关心tty_driver)。
spinlock_t lock; /* 串口端口锁 */ unsigned int iobase; /* IO端口基地址 */ unsigned char __iomem *membase; /* IO内存基地址,经映射(如ioremap)后的IO内存虚拟基地址 */ unsigned int irq; /* 中断号 */ unsigned int uartclk; /* 串口时钟 */ unsigned int fifosize; /* 串口FIFO缓冲大小 */ unsigned char x_char; /* xon/xoff字符 */ unsigned char regshift; /* 寄存器位移 */ unsigned char iotype; /* IO访问方式 */ unsigned char unused1; #define UPIO_PORT (0) /* IO端口 */ #define UPIO_HUB6 (1) #define UPIO_MEM (2) /* IO内存 */ #define UPIO_MEM32 (3) #define UPIO_AU (4) /* Au1x00 type IO */ #define UPIO_TSI (5) /* Tsi108/109 type IO */ #define UPIO_DWAPB (6) /* DesignWare APB UART */ #define UPIO_RM9000 (7) /* RM9000 type IO */ unsigned int read_status_mask; /* 关心的Rx error status */ unsigned int ignore_status_mask;/* 忽略的Rx error status */ struct uart_info *info; /* pointer to parent info */ struct uart_icount icount; /* 计数器 */ struct console *cons; /* console结构体 */ #ifdef CONFIG_SERIAL_CORE_CONSOLE unsigned long sysrq; /* sysrq timeout */ #endif upf_t flags; #define UPF_FOURPORT ((__force upf_t) (1 1)) #define UPF_SAK ((__force upf_t) (1 2)) #define UPF_SPD_MASK ((__force upf_t) (0x1030)) #define UPF_SPD_HI ((__force upf_t) (0x0010)) #define UPF_SPD_VHI ((__force upf_t) (0x0020)) #define UPF_SPD_CUST ((__force upf_t) (0x0030)) #define UPF_SPD_SHI ((__force upf_t) (0x1000)) #define UPF_SPD_WARP ((__force upf_t) (0x1010)) #define UPF_SKIP_TEST ((__force upf_t) (1 6)) #define UPF_AUTO_IRQ ((__force upf_t) (1 7)) #define UPF_HARDPPS_CD ((__force upf_t) (1 11)) #define UPF_LOW_LATENCY ((__force upf_t) (1 13)) #define UPF_BUGGY_UART ((__force upf_t) (1 14)) #define UPF_MAGIC_MULTIPLIER ((__force upf_t) (1 16)) #define UPF_CONS_FLOW ((__force upf_t) (1 23)) #define UPF_SHARE_IRQ ((__force upf_t) (1 24)) #define UPF_BOOT_AUTOCONF ((__force upf_t) (1 28)) #define UPF_FIXED_PORT ((__force upf_t) (1 29)) #define UPF_DEAD ((__force upf_t) (1 30)) #define UPF_IOREMAP ((__force upf_t) (1 31)) #define UPF_CHANGE_MASK ((__force upf_t) (0x17fff)) #define UPF_USR_MASK ((__force upf_t) (UPF_SPD_MASK|UPF_LOW_LATENCY)) unsigned int mctrl; /* 当前的moden设置 */ unsigned int timeout; /* character-based timeout */ unsigned int type; /* 端口类型 */ const struct uart_ops *ops; /* 串口端口操作函数集 */ unsigned int custom_divisor; unsigned int line; /* 端口索引 */ resource_size_t mapbase; /* IO内存物理基地址,可用于ioremap */ struct device *dev; /* 父设备 */ unsigned char hub6; /* this should be in the 8250 driver */ unsigned char suspended; unsigned char unused[2]; void *private_data; /* 端口私有数据,一般为platform数据指针 */ }; uart_iconut为串口信息计数器,包含了发送字符计数、接收字符计数等。在串口的发送中断处理函数和接收中断处理函数中,我们需要管理这些计数。
}; uart_info有两个成员在底层串口驱动会用到:xmit和tty。用户空间程序通过串口发送数据时,上层驱动将用户数据保存在xmit;而串口发送中断处理函数就是通过xmit获取到用户数据并将它们发送出去。串口接收中断处理函数需要通过tty将接收到的数据传递给行规则层。(未找到)
* This structure describes all the operations that can be * done on the physical hardware. struct uart_ops { unsigned int (*tx_empty)(struct uart_port *); /* 串口的Tx FIFO缓存是否为空 */ void (*set_mctrl)(struct uart_port *, unsigned int mctrl); /* 设置串口modem控制 */ unsigned int (*get_mctrl)(struct uart_port *); /* 获取串口modem控制 */ void (*stop_tx)(struct uart_port *); /* 禁止串口发送数据 */ void (*start_tx)(struct uart_port *); /* 使能串口发送数据 */ void (*send_xchar)(struct uart_port *, char ch);/* 发送xChar */ void (*stop_rx)(struct uart_port *); /* 禁止串口接收数据 */ void (*enable_ms)(struct uart_port *); /* 使能modem的状态信号 */ void (*break_ctl)(struct uart_port *, int ctl); /* 设置break信号 */ int (*startup)(struct uart_port *); /* 启动串口,应用程序打开串口设备文件时,该函数会被调用 */ void (*shutdown)(struct uart_port *); /* 关闭串口,应用程序关闭串口设备文件时,该函数会被调用 */ void (*set_termios)(struct uart_port *, struct ktermios *new, struct ktermios*old); /* 设置串口参数 */ void (*pm)(struct uart_port *, unsigned int state, unsigned int oldstate); /* 串口电源管理 */ int (*set_wake)(struct uart_port *, unsigned int state); /* */ const char *(*type)(struct uart_port *); /* 返回一描述串口类型的字符串 */ void (*release_port)(struct uart_port *); /* 释放串口已申请的IO端口/IO内存资源,必要时还需iounmap */ int (*request_port)(struct uart_port *); /* 申请必要的IO端口/IO内存资源,必要时还可以重新映射串口端口 */ void (*config_port)(struct uart_port *, int); /* 执行串口所需的自动配置 */ int (*verify_port)(struct uart_port *, struct serial_struct *); /* 核实新串口的信息 */ int (*ioctl)(struct uart_port *, unsigned int, unsigned long); /* IO控制 */ };
1、uart_register_driver
2、uart_unregister_driver
3、uart_add_one_port
4、uart_remove_one_port
5、uart_write_wakeup
6、uart_suspend_port
7、uart_resume_port
8、uart_get_baud_rate
9、uart_get_divisor
10、uart_update_timeout
11、uart_match_port
12、uart_console_write
三、串口驱动例子 该串口驱动例子是我针对s3c2410处理器的串口2(uart2)独立开发的。因为我通过博创2410s开发板的GRPS扩展板来测试该驱动(已通过测试),所以我叫该串口为gprs_uart。该驱动将串口看作平台(platform)设备。platform可以看作一伪总线,用于将集成于片上系统的轻量级设备与Linux设备驱动模型联系到一起,它包含以下两部分(有关platform的声明都在#include linux/platform_device.h ,具体实现在drivers/base/platform.c):
1、platform设备。我们需要为每个设备定义一个platform_device实例
const char *name; /* 设备名 */ int id; /* 设备的id号 */ struct device dev; /* 其对应的device */ u32 num_resources;/* 该设备用有的资源数 */ struct resource *resource; /* 资源数组 */ }; 为我们的设备创建platform_device实例有两种方法:①填充一个platform_device结构体后用platform_device_register(一次注册一个)或②platform_add_devices(一次可以注册多个platform设备)将platform_device注册到内核;更简单的是使用platform_device_register_simple来建立并注册我们的platform_device。
2、platform驱动。platform设备由platform驱动进行管理。当设备加入到系统中时,platform_driver的probe方法会被调用来见对应的设备添加或者注册到内核;当设备从系统中移除时,platform_driver的remove方法会被调用来做一些清理工作,如移除该设备的一些实例、注销一些已注册到系统中去的东西。
#include linux/kernel.h /* printk() */ #include linux/slab.h /* kmalloc() */ #include linux/fs.h /* everything... */ #include linux/errno.h /* error codes */ #include linux/types.h /* size_t */ #include linux/fcntl.h /* O_ACCMODE */ #include asm/system.h /* cli(), *_flags */ #include asm/uaccess.h /* copy_*_user */ #include linux/ioctl.h #include linux/device.h #include linux/platform_device.h #include linux/sysrq.h #include linux/tty.h #include linux/tty_flip.h #include linux/serial_core.h #include linux/serial.h #include linux/delay.h #include linux/clk.h #include linux/console.h #include asm/io.h #include asm/irq.h #include asm/hardware.h #include asm/plat-s3c/regs-serial.h #include asm/arch/regs-gpio.h
#define DEV_NAME "gprs_uart" /* 设备名 */ /* 这里将串口的主设备号设为0,则串口设备编号由内核动态分配;你也可指定串口的设备编号 */ #define GPRS_UART_MAJOR 0 /* 主设备号 */ #define GPRS_UART_MINOR 0 /* 次设备号 */ #define GPRS_UART_FIFO_SIZE 16 /* 串口FIFO的大小 */ #define RXSTAT_DUMMY_READ (0x10000000) #define MAP_SIZE (0x100) /* 要映射的串口IO内存区大小 */ /* 串口发送中断号 */ #define TX_IRQ(port) ((port)- irq + 1) /* 串口接收中断号 */ #define RX_IRQ(port) ((port)- irq) /* 允许串口接收字符的标志 */ #define tx_enabled(port) ((port)- unused[0]) /* 允许串口发送字符的标志 */ #define rx_enabled(port) ((port)- unused[1]) /* 获取寄存器地址 */ #define portaddr(port, reg) ((port)- membase + (reg)) /* 读8位宽的寄存器 */ #define rd_regb(port, reg) (ioread8(portaddr(port, reg))) /* 读32位宽的寄存器 */ #define rd_regl(port, reg) (ioread32(portaddr(port, reg))) /* 写8位宽的寄存器 */ #define wr_regb(port, reg, val) \ do { iowrite8(val, portaddr(port, reg)); } while(0) /* 写32位宽的寄存器 */ #define wr_regl(port, reg, val) \ do { iowrite32(val, portaddr(port, reg)); } while(0)
disable_irq(TX_IRQ(port)); /* 禁止发送中断 */ tx_enabled(port) = 0; /* 设置串口为未启动发送 */ } /* 使能串口发送数据 */ static void gprs_uart_start_tx(struct uart_port *port) if (!tx_enabled(port)) /* 若串口未启动发送 */ { enable_irq(TX_IRQ(port)); /* 使能发送中断 */ tx_enabled(port) = 1; /* 设置串口为已启动发送 */ } /* 禁止串口接收数据 */ static void gprs_uart_stop_rx(struct uart_port *port) if (rx_enabled(port)) /* 若串口已启动接收 */ { disable_irq(RX_IRQ(port)); /* 禁止接收中断 */ rx_enabled(port) = 0; /* 设置串口为未启动接收 */ } /* 使能modem的状态信号 */ static void gprs_uart_enable_ms(struct uart_port *port) /* 串口的Tx FIFO缓存是否为空 */ static unsigned int gprs_uart_tx_empty(struct uart_port *port) int ret = 1; unsigned long ufstat = rd_regl(port, S3C2410_UFSTAT); unsigned long ufcon = rd_regl(port, S3C2410_UFCON); if (ufcon S3C2410_UFCON_FIFOMODE) /* 若使能了FIFO */ { if ((ufstat S3C2410_UFSTAT_TXMASK) != 0 || /* 0 FIFO =15 */ (ufstat S3C2410_UFSTAT_TXFULL)) /* FIFO满 */ ret = 0; } else /* 若未使能了FIFO,则判断发送缓存和发送移位寄存器是否均为空 */ { ret = rd_regl(port, S3C2410_UTRSTAT) S3C2410_UTRSTAT_TXE; } return ret; /* 获取串口modem控制,因为uart2无modem控制,所以CTS、DSR直接返回有效 */ static unsigned int gprs_uart_get_mctrl(struct uart_port *port) return (TIOCM_CTS | TIOCM_DSR | TIOCM_CAR); /* 设置串口modem控制 */ static void gprs_uart_set_mctrl(struct uart_port *port, unsigned int mctrl) /* 设置break信号 */ static void gprs_uart_break_ctl(struct uart_port *port, int break_state) unsigned long flags; unsigned int ucon; spin_lock_irqsave( port- lock, flags); ucon = rd_regl(port, S3C2410_UCON); if (break_state) ucon |= S3C2410_UCON_SBREAK; else ucon = ~S3C2410_UCON_SBREAK; wr_regl(port, S3C2410_UCON, ucon); spin_unlock_irqrestore( port- lock, flags); /* 返回Rx FIFO已存多少数据 */ static int gprs_uart_rx_fifocnt(unsigned long ufstat) /* 若Rx FIFO已满,返回FIFO的大小 */ if (ufstat S3C2410_UFSTAT_RXFULL) return GPRS_UART_FIFO_SIZE; /* 若FIFO未满,返回Rx FIFO已存了多少字节数据 */ return (ufstat S3C2410_UFSTAT_RXMASK) S3C2410_UFSTAT_RXSHIFT; #define S3C2410_UERSTAT_PARITY (0x1000) /* 串口接收中断处理函数,获取串口接收到的数据,并将这些数据递交给行规则层 */ static irqreturn_t gprs_uart_rx_chars(int irq, void *dev_id) struct uart_port *port = dev_id; struct tty_struct *tty = port- info- unsigned int ufcon, ch, flag, ufstat, uerstat; int max_count = 64; /* 循环接收数据,最多一次中断接收64字节数据 */ while (max_count-- 0) { ufcon = rd_regl(port, S3C2410_UFCON); ufstat = rd_regl(port, S3C2410_UFSTAT); /* 若Rx FIFO无数据了,跳出循环 */ if (gprs_uart_rx_fifocnt(ufstat) == 0) break; /* 读取Rx error状态寄存器 */ uerstat = rd_regl(port, S3C2410_UERSTAT); /* 读取已接受到的数据 */ ch = rd_regb(port, S3C2410_URXH); /* insert the character into the buffer */ /* 先将tty标志设为正常 */ flag = TTY_NORMAL; /* 递增接收字符计数器 */ port- icount.rx++; /* 判断是否存在Rx error * if (unlikely(uerstat S3C2410_UERSTAT_ANY))等同于 * if (uerstat S3C2410_UERSTAT_ANY) * 只是unlikely表示uerstat S3C2410_UERSTAT_ANY的值为假的可能性大一些 * 另外还有一个likely(value)表示value的值为真的可能性更大一些 */ if (unlikely(uerstat S3C2410_UERSTAT_ANY)) { /* 若break错误,递增icount.brk计算器 */ if (uerstat S3C2410_UERSTAT_BREAK) { port- icount.brk++; if (uart_handle_break(port)) goto ignore_char; } /* 若frame错误,递增icount.frame计算器 */ if (uerstat S3C2410_UERSTAT_FRAME) port- icount.frame++; /* 若overrun错误,递增icount.overrun计算器 */ if (uerstat S3C2410_UERSTAT_OVERRUN) port- icount.overrun++; /* 查看我们是否关心该Rx error * port- read_status_mask保存着我们感兴趣的Rx error status */ uerstat = port- read_status_mask; /* 若我们关心该Rx error,则将flag设置为对应的error flag */ if (uerstat S3C2410_UERSTAT_BREAK) flag = TTY_BREAK; else if (uerstat S3C2410_UERSTAT_PARITY) flag = TTY_PARITY; else if (uerstat ( S3C2410_UERSTAT_FRAME | S3C2410_UERSTAT_OVERRUN)) flag = TTY_FRAME; } /* 处理sys字符 */ if (uart_handle_sysrq_char(port, ch)) goto ignore_char; /* 将接收到的字符插入到tty设备的flip缓冲 */ uart_insert_char(port, uerstat, S3C2410_UERSTAT_OVERRUN, ch, flag); ignore_char: continue; } /* 刷新tty设备的flip缓冲,将接受到的数据传给行规则层 */ tty_flip_buffer_push(tty); return IRQ_HANDLED; /* 串口发送中断处理函数,将用户空间的数据(保存在环形缓冲xmit里)发送出去 */ static irqreturn_t gprs_uart_tx_chars(int irq, void *dev_id) struct uart_port *port = dev_id; struct circ_buf *xmit = port- info- xmit; /* 获取环线缓冲 */ int count = 256; /* 若设置了xChar字符 */ if (port- x_char) { /* 将该xChar发送出去 */ wr_regb(port, S3C2410_UTXH, port- x_char); /* 递增发送计数 */ port- icount.tx++; /* 清除xChar */ port- x_char = 0; /* 退出中断处理 */ goto out; } /* 如果没有更多的字符需要发送(环形缓冲为空), * 或者uart Tx已停止, * 则停止uart并退出中断处理函数 */ if (uart_circ_empty(xmit) || uart_tx_stopped(port)) { gprs_uart_stop_tx(port); goto out; } /* 循环发送数据,直到环形缓冲为空,最多一次中断发送256字节数据 */ while (!uart_circ_empty(xmit) count-- 0) { /* 若Tx FIFO已满,退出循环 */ if (rd_regl(port, S3C2410_UFSTAT) S3C2410_UFSTAT_TXFULL) break; /* 将要发送的数据写入Tx FIFO */ wr_regb(port, S3C2410_UTXH, xmit- buf[xmit- tail]); /* 移向循环缓冲中下一要发送的数据 */ xmit- tail = (xmit- tail + 1) (UART_XMIT_SIZE - 1); port- icount.tx++; } /* 如果环形缓冲区中剩余的字符少于WAKEUP_CHARS,唤醒上层 */ if (uart_circ_chars_pending(xmit) WAKEUP_CHARS) uart_write_wakeup(port); /* 如果环形缓冲为空,则停止发送 */ if (uart_circ_empty(xmit)) gprs_uart_stop_tx(port); out: return IRQ_HANDLED; /* 启动串口端口,在打开该驱动的设备文件时会调用该函数来申请串口中断,并设置串口为可接受,也可发送 */ static int gprs_uart_startup(struct uart_port *port) unsigned long flags; int ret; const char *portname = to_platform_device(port- dev)- name; /* 设置串口为不可接受,也不可发送 */ rx_enabled(port) = 0; tx_enabled(port) = 0; spin_lock_irqsave( port- lock, flags); /* 申请接收中断 */ ret = request_irq(RX_IRQ(port), gprs_uart_rx_chars, 0, portname, port); if (ret != 0) { printk(KERN_ERR "cannot get irq %d\n", RX_IRQ(port)); return ret; } /* 设置串口为允许接收 */ rx_enabled(port) = 1; /* 申请发送中断 */ ret = request_irq(TX_IRQ(port), gprs_uart_tx_chars, 0, portname, port); if (ret) { printk(KERN_ERR "cannot get irq %d\n", TX_IRQ(port)); rx_enabled(port) = 0; free_irq(RX_IRQ(port), port); goto err; } /* 设置串口为允许发送 */ tx_enabled(port) = 1; spin_unlock_irqrestore( port- lock, flags); return ret; /* 关闭串口,在关闭驱动的设备文件时会调用该函数,释放串口中断 */ static void gprs_uart_shutdown(struct uart_port *port) rx_enabled(port) = 0; /* 设置串口为不允许接收 */ free_irq(RX_IRQ(port), port); /* 释放接收中断 */ tx_enabled(port) = 0; /* 设置串口为不允许发送 */ free_irq(TX_IRQ(port), port); /* 释放发送中断 */ /* 设置串口参数 */ static void gprs_uart_set_termios(struct uart_port *port, struct ktermios *termios, struct ktermios *old) unsigned long flags; unsigned int baud, quot; unsigned int ulcon, ufcon = 0; /* 不支持moden控制信号线 * HUPCL: 关闭时挂断moden * CMSPAR: mark or space (stick) parity * CLOCAL: 忽略任何moden控制线 */ termios- c_cflag = ~(HUPCL | CMSPAR); termios- c_cflag |= CLOCAL; /* 获取用户设置的串口波特率,并计算分频数(串口波特率除数quot) */ baud = uart_get_baud_rate(port, termios, old, 0, 115200*8); if (baud == 38400 (port- flags UPF_SPD_MASK) == UPF_SPD_CUST) quot = port- custom_divisor; else quot = port- uartclk / baud / 16 - 1; /* 设置数据字长 */ switch (termios- c_cflag CSIZE) { case CS5: ulcon = S3C2410_LCON_CS5; break; case CS6: ulcon = S3C2410_LCON_CS6; break; case CS7: ulcon = S3C2410_LCON_CS7; break; case CS8: default: ulcon = S3C2410_LCON_CS8; break; } /* 是否要求设置两个停止位(CSTOPB) */ if (termios- c_cflag CSTOPB) ulcon |= S3C2410_LCON_STOPB; /* 是否使用奇偶检验 */ if (termios- c_cflag PARENB) { if (termios- c_cflag PARODD) /* 奇校验 */ ulcon |= S3C2410_LCON_PODD; else /* 偶校验 */ ulcon |= S3C2410_LCON_PEVEN; } else /* 无校验 */ { ulcon |= S3C2410_LCON_PNONE; } if (port- fifosize 1) ufcon |= S3C2410_UFCON_FIFOMODE | S3C2410_UFCON_RXTRIG8; spin_lock_irqsave( port- lock, flags); /* 设置FIFO控制寄存器、线控制寄存器和波特率除数寄存器 */ wr_regl(port, S3C2410_UFCON, ufcon); wr_regl(port, S3C2410_ULCON, ulcon); wr_regl(port, S3C2410_UBRDIV, quot); /* 更新串口FIFO的超时时限 */ uart_update_timeout(port, termios- c_cflag, baud); /* 设置我们感兴趣的Rx error */ port- read_status_mask = S3C2410_UERSTAT_OVERRUN; if (termios- c_iflag INPCK) port- read_status_mask |= S3C2410_UERSTAT_FRAME | S3C2410_UERSTAT_PARITY; /* 设置我们忽略的Rx error */ port- ignore_status_mask = 0; if (termios- c_iflag IGNPAR) port- ignore_status_mask |= S3C2410_UERSTAT_OVERRUN; if (termios- c_iflag IGNBRK termios- c_iflag IGNPAR) port- ignore_status_mask |= S3C2410_UERSTAT_FRAME; /* 若未设置CREAD(使用接收器),则忽略所有Rx error*/ if ((termios- c_cflag CREAD) == 0) port- ignore_status_mask |= RXSTAT_DUMMY_READ; spin_unlock_irqrestore( port- lock, flags); /* 获取串口类型 */ static const char *gprs_uart_type(struct uart_port *port) {/* 返回描述串口类型的字符串指针 */ return port- type == PORT_S3C2410 ? "gprs_uart:s3c2410_uart2" : NULL; /* 申请串口一些必要的资源,如IO端口/IO内存资源,必要时还可以重新映射串口端口 */ static int gprs_uart_request_port(struct uart_port *port) struct resource *res; const char *name = to_platform_device(port- dev)- name; /* request_mem_region请求分配IO内存,从开始port- mapbase,大小MAP_SIZE * port- mapbase保存当前串口的寄存器基地址(物理) * uart2: 0x50008000 */ res = request_mem_region(port- mapbase, MAP_SIZE, name); if (res == NULL) { printk(KERN_ERR"request_mem_region error: %p\n", res); return -EBUSY; } return 0; /* 释放串口已申请的IO端口/IO内存资源,必要时还需iounmap */ static void gprs_uart_release_port(struct uart_port *port) /* 释放已分配IO内存 */ release_mem_region(port- mapbase, MAP_SIZE); /* 执行串口所需的自动配置 */ static void gprs_uart_config_port(struct uart_port *port, int flags) { int retval; /* 请求串口 */ retval = gprs_uart_request_port(port); /* 设置串口类型 */ if (flags UART_CONFIG_TYPE retval == 0) port- type = PORT_S3C2410; /* The UART operations structure */ static struct uart_ops gprs_uart_ops = { .start_tx = gprs_uart_start_tx, /* Start transmitting */ .stop_tx = gprs_uart_stop_tx, /* Stop transmission */ .stop_rx = gprs_uart_stop_rx, /* Stop reception */ .enable_ms = gprs_uart_enable_ms, /* Enable modem status signals */ .tx_empty = gprs_uart_tx_empty, /* Transmitter busy? */ .get_mctrl = gprs_uart_get_mctrl, /* Get modem control */ .set_mctrl = gprs_uart_set_mctrl, /* Set modem control */ .break_ctl = gprs_uart_break_ctl, /* Set break signal */ .startup = gprs_uart_startup, /* App opens GPRS_UART */ .shutdown = gprs_uart_shutdown, /* App closes GPRS_UART */ .set_termios = gprs_uart_set_termios, /* Set termios */ .type = gprs_uart_type, /* Get UART type */ .request_port = gprs_uart_request_port, /* Claim resources associated with a GPRS_UART port */ .release_port = gprs_uart_release_port, /* Release resources associated with a GPRS_UART port */ .config_port = gprs_uart_config_port, /* Configure when driver adds a GPRS_UART port */ /* Uart driver for GPRS_UART */ static struct uart_driver gprs_uart_driver = { .owner = THIS_MODULE, /* Owner */ .driver_name = DEV_NAME, /* Driver name */ .dev_name = DEV_NAME, /* Device node name */ .major = GPRS_UART_MAJOR, /* Major number */ .minor = GPRS_UART_MINOR, /* Minor number start */ .nr = 1, /* Number of UART ports */ /* Uart port for GPRS_UART port */ static struct uart_port gprs_uart_port = { .irq = IRQ_S3CUART_RX2, /* IRQ */ .fifosize = GPRS_UART_FIFO_SIZE, /* Size of the FIFO */ .iotype = UPIO_MEM, /* IO memory */ .flags = UPF_BOOT_AUTOCONF, /* UART port flag */ .ops = gprs_uart_ops, /* UART operations */ .line = 0, /* UART port number */ .lock = __SPIN_LOCK_UNLOCKED(gprs_uart_port.lock), /* 初始化指定串口端口 */ static int gprs_uart_init_port(struct uart_port *port, struct platform_device *platdev) unsigned long flags; unsigned int gphcon; if (platdev == NULL) return -ENODEV; port- dev = platdev- /* 设置串口波特率时钟频率 */ port- uartclk = clk_get_rate(clk_get( platdev- dev, "pclk")); /* 设置串口的寄存器基地址(物理): 0x50008000 */ port- mapbase = S3C2410_PA_UART2; /* 设置当前串口的寄存器基地址(虚拟): 0xF5008000 */ port- membase = S3C24XX_VA_UART + (S3C2410_PA_UART2 - S3C24XX_PA_UART); spin_lock_irqsave( port- lock, flags); wr_regl(port, S3C2410_UCON, S3C2410_UCON_DEFAULT); wr_regl(port, S3C2410_ULCON, S3C2410_LCON_CS8 | S3C2410_LCON_PNONE); wr_regl(port, S3C2410_UFCON, S3C2410_UFCON_FIFOMODE | S3C2410_UFCON_RXTRIG8 | S3C2410_UFCON_RESETBOTH); /* 将I/O port H的gph6和gph7设置为TXD2和RXD2 */ gphcon = readl(S3C2410_GPHCON); gphcon = ~((0x5) 12); writel(gphcon, S3C2410_GPHCON); spin_unlock_irqrestore( port- lock, flags); return 0; /* Platform driver probe */ static int __init gprs_uart_probe(struct platform_device *dev) int ret; /* 初始化串口 */ ret = gprs_uart_init_port( gprs_uart_port, dev); if (ret 0) { printk(KERN_ERR"gprs_uart_probe: gprs_uart_init_port error: %d\n", ret); return ret; } /* 添加串口 */ ret = uart_add_one_port( gprs_uart_driver, gprs_uart_port); if (ret 0) { printk(KERN_ERR"gprs_uart_probe: uart_add_one_port error: %d\n", ret); return ret; } /* 将串口uart_port结构体保存在platform_device- dev- driver_data中 */ platform_set_drvdata(dev, gprs_uart_port); return 0; /* Called when the platform driver is unregistered */ static int gprs_uart_remove(struct platform_device *dev) platform_set_drvdata(dev, NULL); /* 移除串口 */ uart_remove_one_port( gprs_uart_driver, gprs_uart_port); return 0; /* Suspend power management event */ static int gprs_uart_suspend(struct platform_device *dev, pm_message_t state) uart_suspend_port( gprs_uart_driver, gprs_uart_port); return 0; /* Resume after a previous suspend */ static int gprs_uart_resume(struct platform_device *dev) uart_resume_port( gprs_uart_driver, gprs_uart_port); return 0; /* Platform driver for GPRS_UART */ static struct platform_driver gprs_plat_driver = { .probe = gprs_uart_probe, /* Probe method */ .remove = __exit_p(gprs_uart_remove), /* Detach method */ .suspend = gprs_uart_suspend, /* Power suspend */ .resume = gprs_uart_resume, /* Resume after a suspend */ .driver = { .owner = THIS_MODULE, .name = DEV_NAME, /* Driver name */ }, /* Platform device for GPRS_UART */ struct platform_device *gprs_plat_device; static int __init gprs_init_module(void) int retval; /* Register uart_driver for GPRS_UART */ retval = uart_register_driver( gprs_uart_driver); if (0 != retval) { printk(KERN_ERR "gprs_init_module: cant register the GPRS_UART driver %d\n",retval); return retval; } /* Register platform device for GPRS_UART. Usually called during architecture-specific setup */ gprs_plat_device = platform_device_register_simple(DEV_NAME, 0, NULL, 0); if (IS_ERR(gprs_plat_device)) { retval = PTR_ERR(gprs_plat_device); printk(KERN_ERR "gprs_init_module: cant register platform device %d\n", retval); goto fail_reg_plat_dev; } /* Announce a matching driver for the platform devices registered above */ retval = platform_driver_register( gprs_plat_driver); if (0 != retval) { printk(KERN_ERR "gprs_init_module: cant register platform driver %d\n", retval); goto fail_reg_plat_drv; } return 0; /* succeed */ fail_reg_plat_drv: platform_device_unregister(gprs_plat_device); fail_reg_plat_dev: uart_unregister_driver( gprs_uart_driver); return retval; static void __exit gprs_exit_module(void) /* The order of unregistration is important. Unregistering the UART driver before the platform driver will crash the system */ /* Unregister the platform driver */ platform_driver_unregister( gprs_plat_driver); /* Unregister the platform devices */ platform_device_unregister(gprs_plat_device); /* Unregister the GPRS_UART driver */ uart_unregister_driver( gprs_uart_driver); module_init(gprs_init_module); module_exit(gprs_exit_module); MODULE_AUTHOR("lingd"); MODULE_LICENSE("Dual BSD/GPL");
zynq操作系统: Linux驱动开发串口篇 串口( UART)是一种非常常见的外设, 串口在嵌入式开发领域当中一般作为一种调试手段,通过串口将调试信息打印出来,或者通过串口发送指令给主机端进行处理;当然除了作为基本的调试手段之外,还可以通过串口与其他设备或传感器进行通信, 譬如有些 sensor 就使用了串口通信的方式与主机端进行数据交互。
Linux串口驱动程序(3)-打开设备 Linux串口驱动程序(3)-打开设备先来分析一下串口打开的过程: 1、用户调用open函数打开串口设备文件;2、在内核中通过tty子系统,把open操作层层传递到串口驱动程序中;3、在串口驱动程序中的xx_open最终实现这个操作。
1、uart_driver uart_driver包含了串口设备名、串口驱动名、主次设备号、串口控制台(可选)等信息,还封装了tty_driver(底层串口驱动无需关心tty_driver)。
struct uart_driver { struct module *owner; /* 拥有该uart_driver的模块,一般为THIS_MODULE */ const char *driver_name; /* 串口驱动名,串口设备文件名以驱动名为基础 */ const char *dev_name; /* 串口设备名 */ int major; /* 主设备号 */ int minor; /* 次设备号 */ int nr; /* 该uart_driver支持的串口个数(最大) */ struct console *cons; /* 其对应的console.若该uart_driver支持serial console,否则为NULL */ /* * these are private; the low level driver should not * touch these; they should be initialised to NULL */ struct uart_state *state; struct tty_driver *tty_driver; };2、uart_port uart_port用于描述串口端口的I/O端口或I/O内存地址、FIFO大小、端口类型、串口时钟等信息。实际上,一个uart_port实例对应一个串口设备。
spinlock_t lock; /* 串口端口锁 */ unsigned int iobase; /* IO端口基地址 */ unsigned char __iomem *membase; /* IO内存基地址,经映射(如ioremap)后的IO内存虚拟基地址 */ unsigned int irq; /* 中断号 */ unsigned int uartclk; /* 串口时钟 */ unsigned int fifosize; /* 串口FIFO缓冲大小 */ unsigned char x_char; /* xon/xoff字符 */ unsigned char regshift; /* 寄存器位移 */ unsigned char iotype; /* IO访问方式 */ unsigned char unused1; #define UPIO_PORT (0) /* IO端口 */ #define UPIO_HUB6 (1) #define UPIO_MEM (2) /* IO内存 */ #define UPIO_MEM32 (3) #define UPIO_AU (4) /* Au1x00 type IO */ #define UPIO_TSI (5) /* Tsi108/109 type IO */ #define UPIO_DWAPB (6) /* DesignWare APB UART */ #define UPIO_RM9000 (7) /* RM9000 type IO */ unsigned int read_status_mask; /* 关心的Rx error status */ unsigned int ignore_status_mask;/* 忽略的Rx error status */ struct uart_info *info; /* pointer to parent info */ struct uart_icount icount; /* 计数器 */ struct console *cons; /* console结构体 */ #ifdef CONFIG_SERIAL_CORE_CONSOLE unsigned long sysrq; /* sysrq timeout */ #endif upf_t flags; #define UPF_FOURPORT ((__force upf_t) (1 1)) #define UPF_SAK ((__force upf_t) (1 2)) #define UPF_SPD_MASK ((__force upf_t) (0x1030)) #define UPF_SPD_HI ((__force upf_t) (0x0010)) #define UPF_SPD_VHI ((__force upf_t) (0x0020)) #define UPF_SPD_CUST ((__force upf_t) (0x0030)) #define UPF_SPD_SHI ((__force upf_t) (0x1000)) #define UPF_SPD_WARP ((__force upf_t) (0x1010)) #define UPF_SKIP_TEST ((__force upf_t) (1 6)) #define UPF_AUTO_IRQ ((__force upf_t) (1 7)) #define UPF_HARDPPS_CD ((__force upf_t) (1 11)) #define UPF_LOW_LATENCY ((__force upf_t) (1 13)) #define UPF_BUGGY_UART ((__force upf_t) (1 14)) #define UPF_MAGIC_MULTIPLIER ((__force upf_t) (1 16)) #define UPF_CONS_FLOW ((__force upf_t) (1 23)) #define UPF_SHARE_IRQ ((__force upf_t) (1 24)) #define UPF_BOOT_AUTOCONF ((__force upf_t) (1 28)) #define UPF_FIXED_PORT ((__force upf_t) (1 29)) #define UPF_DEAD ((__force upf_t) (1 30)) #define UPF_IOREMAP ((__force upf_t) (1 31)) #define UPF_CHANGE_MASK ((__force upf_t) (0x17fff)) #define UPF_USR_MASK ((__force upf_t) (UPF_SPD_MASK|UPF_LOW_LATENCY)) unsigned int mctrl; /* 当前的moden设置 */ unsigned int timeout; /* character-based timeout */ unsigned int type; /* 端口类型 */ const struct uart_ops *ops; /* 串口端口操作函数集 */ unsigned int custom_divisor; unsigned int line; /* 端口索引 */ resource_size_t mapbase; /* IO内存物理基地址,可用于ioremap */ struct device *dev; /* 父设备 */ unsigned char hub6; /* this should be in the 8250 driver */ unsigned char suspended; unsigned char unused[2]; void *private_data; /* 端口私有数据,一般为platform数据指针 */ }; uart_iconut为串口信息计数器,包含了发送字符计数、接收字符计数等。在串口的发送中断处理函数和接收中断处理函数中,我们需要管理这些计数。
}; uart_info有两个成员在底层串口驱动会用到:xmit和tty。用户空间程序通过串口发送数据时,上层驱动将用户数据保存在xmit;而串口发送中断处理函数就是通过xmit获取到用户数据并将它们发送出去。串口接收中断处理函数需要通过tty将接收到的数据传递给行规则层。(未找到)
/* uart_info实例仅在串口端口打开时有效,它可能在串口关闭时被串口核心层释放。因此,在使用uart_port的uart_info成员时必须保证串口已打开。底层驱动和核心层驱动都可以修改uart_info实例。 * This is the state information which is only valid when the port * is open; it may be freed by the core driver once the device has * been closed. Either the low level driver or the core can modify * stuff here. struct uart_info { struct tty_struct *tty; struct circ_buf xmit; uif_t flags; * Definitions for info- flags. These are _private_ to serial_core, and * are specific to this structure. They may be queried by low level drivers. #define UIF_CHECK_CD ((__force uif_t) (1 25)) #define UIF_CTS_FLOW ((__force uif_t) (1 26)) #define UIF_NORMAL_ACTIVE ((__force uif_t) (1 29)) #define UIF_INITIALIZED ((__force uif_t) (1 31)) #define UIF_SUSPENDED ((__force uif_t) (1 30)) int blocked_open; struct tasklet_struct tlet; wait_queue_head_t open_wait; wait_queue_head_t delta_msr_wait; };3、uart_ops uart_ops涵盖了串口驱动可对串口设备进行的所有操作。
* This structure describes all the operations that can be * done on the physical hardware. struct uart_ops { unsigned int (*tx_empty)(struct uart_port *); /* 串口的Tx FIFO缓存是否为空 */ void (*set_mctrl)(struct uart_port *, unsigned int mctrl); /* 设置串口modem控制 */ unsigned int (*get_mctrl)(struct uart_port *); /* 获取串口modem控制 */ void (*stop_tx)(struct uart_port *); /* 禁止串口发送数据 */ void (*start_tx)(struct uart_port *); /* 使能串口发送数据 */ void (*send_xchar)(struct uart_port *, char ch);/* 发送xChar */ void (*stop_rx)(struct uart_port *); /* 禁止串口接收数据 */ void (*enable_ms)(struct uart_port *); /* 使能modem的状态信号 */ void (*break_ctl)(struct uart_port *, int ctl); /* 设置break信号 */ int (*startup)(struct uart_port *); /* 启动串口,应用程序打开串口设备文件时,该函数会被调用 */ void (*shutdown)(struct uart_port *); /* 关闭串口,应用程序关闭串口设备文件时,该函数会被调用 */ void (*set_termios)(struct uart_port *, struct ktermios *new, struct ktermios*old); /* 设置串口参数 */ void (*pm)(struct uart_port *, unsigned int state, unsigned int oldstate); /* 串口电源管理 */ int (*set_wake)(struct uart_port *, unsigned int state); /* */ const char *(*type)(struct uart_port *); /* 返回一描述串口类型的字符串 */ void (*release_port)(struct uart_port *); /* 释放串口已申请的IO端口/IO内存资源,必要时还需iounmap */ int (*request_port)(struct uart_port *); /* 申请必要的IO端口/IO内存资源,必要时还可以重新映射串口端口 */ void (*config_port)(struct uart_port *, int); /* 执行串口所需的自动配置 */ int (*verify_port)(struct uart_port *, struct serial_struct *); /* 核实新串口的信息 */ int (*ioctl)(struct uart_port *, unsigned int, unsigned long); /* IO控制 */ };
1、uart_register_driver
2、uart_unregister_driver
3、uart_add_one_port
4、uart_remove_one_port
5、uart_write_wakeup
6、uart_suspend_port
7、uart_resume_port
8、uart_get_baud_rate
9、uart_get_divisor
10、uart_update_timeout
11、uart_match_port
12、uart_console_write
三、串口驱动例子 该串口驱动例子是我针对s3c2410处理器的串口2(uart2)独立开发的。因为我通过博创2410s开发板的GRPS扩展板来测试该驱动(已通过测试),所以我叫该串口为gprs_uart。该驱动将串口看作平台(platform)设备。platform可以看作一伪总线,用于将集成于片上系统的轻量级设备与Linux设备驱动模型联系到一起,它包含以下两部分(有关platform的声明都在#include linux/platform_device.h ,具体实现在drivers/base/platform.c):
1、platform设备。我们需要为每个设备定义一个platform_device实例
const char *name; /* 设备名 */ int id; /* 设备的id号 */ struct device dev; /* 其对应的device */ u32 num_resources;/* 该设备用有的资源数 */ struct resource *resource; /* 资源数组 */ }; 为我们的设备创建platform_device实例有两种方法:①填充一个platform_device结构体后用platform_device_register(一次注册一个)或②platform_add_devices(一次可以注册多个platform设备)将platform_device注册到内核;更简单的是使用platform_device_register_simple来建立并注册我们的platform_device。
2、platform驱动。platform设备由platform驱动进行管理。当设备加入到系统中时,platform_driver的probe方法会被调用来见对应的设备添加或者注册到内核;当设备从系统中移除时,platform_driver的remove方法会被调用来做一些清理工作,如移除该设备的一些实例、注销一些已注册到系统中去的东西。
struct platform_driver { int (*probe)(struct platform_device *); int (*remove)(struct platform_device *); void (*shutdown)(struct platform_device *); int (*suspend)(struct platform_device *, pm_message_t state); int (*suspend_late)(struct platform_device *, pm_message_t state); int (*resume_early)(struct platform_device *); int (*resume)(struct platform_device *); struct device_driver driver; };例子驱动中申请和释放IO内存区的整个过程如下: insmod gprs_uart.ko→gprs_init_module()→uart_register_driver()→gprs_uart_probe()→ uart_add_one_port()→gprs_uart_config_port()→gprs_uart_request_port()→request_mem_region() rmmod gprs_uart.ko→gprs_exit_module()→uart_unregister_driver()→gprs_uart_remove()→uart_remove_one_port()→gprs_uart_release_port()→release_mem_region() 例子驱动中申请和释放IRQ资源的整个过程如下: open /dev/gprs_uart→gprs_uart_startup()→request_irq() close /dev/gprs_uart→gprs_uart_shutdown()→free_irq() 想了解更详细的调用过程可以在驱动模块各函数头插入printk(KERN_DEBUG "%s\n", __FUNCTION__);并在函数尾插入printk(KERN_DEBUG "%s done\n", __FUNCTION__);
#include linux/kernel.h /* printk() */ #include linux/slab.h /* kmalloc() */ #include linux/fs.h /* everything... */ #include linux/errno.h /* error codes */ #include linux/types.h /* size_t */ #include linux/fcntl.h /* O_ACCMODE */ #include asm/system.h /* cli(), *_flags */ #include asm/uaccess.h /* copy_*_user */ #include linux/ioctl.h #include linux/device.h #include linux/platform_device.h #include linux/sysrq.h #include linux/tty.h #include linux/tty_flip.h #include linux/serial_core.h #include linux/serial.h #include linux/delay.h #include linux/clk.h #include linux/console.h #include asm/io.h #include asm/irq.h #include asm/hardware.h #include asm/plat-s3c/regs-serial.h #include asm/arch/regs-gpio.h
#define DEV_NAME "gprs_uart" /* 设备名 */ /* 这里将串口的主设备号设为0,则串口设备编号由内核动态分配;你也可指定串口的设备编号 */ #define GPRS_UART_MAJOR 0 /* 主设备号 */ #define GPRS_UART_MINOR 0 /* 次设备号 */ #define GPRS_UART_FIFO_SIZE 16 /* 串口FIFO的大小 */ #define RXSTAT_DUMMY_READ (0x10000000) #define MAP_SIZE (0x100) /* 要映射的串口IO内存区大小 */ /* 串口发送中断号 */ #define TX_IRQ(port) ((port)- irq + 1) /* 串口接收中断号 */ #define RX_IRQ(port) ((port)- irq) /* 允许串口接收字符的标志 */ #define tx_enabled(port) ((port)- unused[0]) /* 允许串口发送字符的标志 */ #define rx_enabled(port) ((port)- unused[1]) /* 获取寄存器地址 */ #define portaddr(port, reg) ((port)- membase + (reg)) /* 读8位宽的寄存器 */ #define rd_regb(port, reg) (ioread8(portaddr(port, reg))) /* 读32位宽的寄存器 */ #define rd_regl(port, reg) (ioread32(portaddr(port, reg))) /* 写8位宽的寄存器 */ #define wr_regb(port, reg, val) \ do { iowrite8(val, portaddr(port, reg)); } while(0) /* 写32位宽的寄存器 */ #define wr_regl(port, reg, val) \ do { iowrite32(val, portaddr(port, reg)); } while(0)
disable_irq(TX_IRQ(port)); /* 禁止发送中断 */ tx_enabled(port) = 0; /* 设置串口为未启动发送 */ } /* 使能串口发送数据 */ static void gprs_uart_start_tx(struct uart_port *port) if (!tx_enabled(port)) /* 若串口未启动发送 */ { enable_irq(TX_IRQ(port)); /* 使能发送中断 */ tx_enabled(port) = 1; /* 设置串口为已启动发送 */ } /* 禁止串口接收数据 */ static void gprs_uart_stop_rx(struct uart_port *port) if (rx_enabled(port)) /* 若串口已启动接收 */ { disable_irq(RX_IRQ(port)); /* 禁止接收中断 */ rx_enabled(port) = 0; /* 设置串口为未启动接收 */ } /* 使能modem的状态信号 */ static void gprs_uart_enable_ms(struct uart_port *port) /* 串口的Tx FIFO缓存是否为空 */ static unsigned int gprs_uart_tx_empty(struct uart_port *port) int ret = 1; unsigned long ufstat = rd_regl(port, S3C2410_UFSTAT); unsigned long ufcon = rd_regl(port, S3C2410_UFCON); if (ufcon S3C2410_UFCON_FIFOMODE) /* 若使能了FIFO */ { if ((ufstat S3C2410_UFSTAT_TXMASK) != 0 || /* 0 FIFO =15 */ (ufstat S3C2410_UFSTAT_TXFULL)) /* FIFO满 */ ret = 0; } else /* 若未使能了FIFO,则判断发送缓存和发送移位寄存器是否均为空 */ { ret = rd_regl(port, S3C2410_UTRSTAT) S3C2410_UTRSTAT_TXE; } return ret; /* 获取串口modem控制,因为uart2无modem控制,所以CTS、DSR直接返回有效 */ static unsigned int gprs_uart_get_mctrl(struct uart_port *port) return (TIOCM_CTS | TIOCM_DSR | TIOCM_CAR); /* 设置串口modem控制 */ static void gprs_uart_set_mctrl(struct uart_port *port, unsigned int mctrl) /* 设置break信号 */ static void gprs_uart_break_ctl(struct uart_port *port, int break_state) unsigned long flags; unsigned int ucon; spin_lock_irqsave( port- lock, flags); ucon = rd_regl(port, S3C2410_UCON); if (break_state) ucon |= S3C2410_UCON_SBREAK; else ucon = ~S3C2410_UCON_SBREAK; wr_regl(port, S3C2410_UCON, ucon); spin_unlock_irqrestore( port- lock, flags); /* 返回Rx FIFO已存多少数据 */ static int gprs_uart_rx_fifocnt(unsigned long ufstat) /* 若Rx FIFO已满,返回FIFO的大小 */ if (ufstat S3C2410_UFSTAT_RXFULL) return GPRS_UART_FIFO_SIZE; /* 若FIFO未满,返回Rx FIFO已存了多少字节数据 */ return (ufstat S3C2410_UFSTAT_RXMASK) S3C2410_UFSTAT_RXSHIFT; #define S3C2410_UERSTAT_PARITY (0x1000) /* 串口接收中断处理函数,获取串口接收到的数据,并将这些数据递交给行规则层 */ static irqreturn_t gprs_uart_rx_chars(int irq, void *dev_id) struct uart_port *port = dev_id; struct tty_struct *tty = port- info- unsigned int ufcon, ch, flag, ufstat, uerstat; int max_count = 64; /* 循环接收数据,最多一次中断接收64字节数据 */ while (max_count-- 0) { ufcon = rd_regl(port, S3C2410_UFCON); ufstat = rd_regl(port, S3C2410_UFSTAT); /* 若Rx FIFO无数据了,跳出循环 */ if (gprs_uart_rx_fifocnt(ufstat) == 0) break; /* 读取Rx error状态寄存器 */ uerstat = rd_regl(port, S3C2410_UERSTAT); /* 读取已接受到的数据 */ ch = rd_regb(port, S3C2410_URXH); /* insert the character into the buffer */ /* 先将tty标志设为正常 */ flag = TTY_NORMAL; /* 递增接收字符计数器 */ port- icount.rx++; /* 判断是否存在Rx error * if (unlikely(uerstat S3C2410_UERSTAT_ANY))等同于 * if (uerstat S3C2410_UERSTAT_ANY) * 只是unlikely表示uerstat S3C2410_UERSTAT_ANY的值为假的可能性大一些 * 另外还有一个likely(value)表示value的值为真的可能性更大一些 */ if (unlikely(uerstat S3C2410_UERSTAT_ANY)) { /* 若break错误,递增icount.brk计算器 */ if (uerstat S3C2410_UERSTAT_BREAK) { port- icount.brk++; if (uart_handle_break(port)) goto ignore_char; } /* 若frame错误,递增icount.frame计算器 */ if (uerstat S3C2410_UERSTAT_FRAME) port- icount.frame++; /* 若overrun错误,递增icount.overrun计算器 */ if (uerstat S3C2410_UERSTAT_OVERRUN) port- icount.overrun++; /* 查看我们是否关心该Rx error * port- read_status_mask保存着我们感兴趣的Rx error status */ uerstat = port- read_status_mask; /* 若我们关心该Rx error,则将flag设置为对应的error flag */ if (uerstat S3C2410_UERSTAT_BREAK) flag = TTY_BREAK; else if (uerstat S3C2410_UERSTAT_PARITY) flag = TTY_PARITY; else if (uerstat ( S3C2410_UERSTAT_FRAME | S3C2410_UERSTAT_OVERRUN)) flag = TTY_FRAME; } /* 处理sys字符 */ if (uart_handle_sysrq_char(port, ch)) goto ignore_char; /* 将接收到的字符插入到tty设备的flip缓冲 */ uart_insert_char(port, uerstat, S3C2410_UERSTAT_OVERRUN, ch, flag); ignore_char: continue; } /* 刷新tty设备的flip缓冲,将接受到的数据传给行规则层 */ tty_flip_buffer_push(tty); return IRQ_HANDLED; /* 串口发送中断处理函数,将用户空间的数据(保存在环形缓冲xmit里)发送出去 */ static irqreturn_t gprs_uart_tx_chars(int irq, void *dev_id) struct uart_port *port = dev_id; struct circ_buf *xmit = port- info- xmit; /* 获取环线缓冲 */ int count = 256; /* 若设置了xChar字符 */ if (port- x_char) { /* 将该xChar发送出去 */ wr_regb(port, S3C2410_UTXH, port- x_char); /* 递增发送计数 */ port- icount.tx++; /* 清除xChar */ port- x_char = 0; /* 退出中断处理 */ goto out; } /* 如果没有更多的字符需要发送(环形缓冲为空), * 或者uart Tx已停止, * 则停止uart并退出中断处理函数 */ if (uart_circ_empty(xmit) || uart_tx_stopped(port)) { gprs_uart_stop_tx(port); goto out; } /* 循环发送数据,直到环形缓冲为空,最多一次中断发送256字节数据 */ while (!uart_circ_empty(xmit) count-- 0) { /* 若Tx FIFO已满,退出循环 */ if (rd_regl(port, S3C2410_UFSTAT) S3C2410_UFSTAT_TXFULL) break; /* 将要发送的数据写入Tx FIFO */ wr_regb(port, S3C2410_UTXH, xmit- buf[xmit- tail]); /* 移向循环缓冲中下一要发送的数据 */ xmit- tail = (xmit- tail + 1) (UART_XMIT_SIZE - 1); port- icount.tx++; } /* 如果环形缓冲区中剩余的字符少于WAKEUP_CHARS,唤醒上层 */ if (uart_circ_chars_pending(xmit) WAKEUP_CHARS) uart_write_wakeup(port); /* 如果环形缓冲为空,则停止发送 */ if (uart_circ_empty(xmit)) gprs_uart_stop_tx(port); out: return IRQ_HANDLED; /* 启动串口端口,在打开该驱动的设备文件时会调用该函数来申请串口中断,并设置串口为可接受,也可发送 */ static int gprs_uart_startup(struct uart_port *port) unsigned long flags; int ret; const char *portname = to_platform_device(port- dev)- name; /* 设置串口为不可接受,也不可发送 */ rx_enabled(port) = 0; tx_enabled(port) = 0; spin_lock_irqsave( port- lock, flags); /* 申请接收中断 */ ret = request_irq(RX_IRQ(port), gprs_uart_rx_chars, 0, portname, port); if (ret != 0) { printk(KERN_ERR "cannot get irq %d\n", RX_IRQ(port)); return ret; } /* 设置串口为允许接收 */ rx_enabled(port) = 1; /* 申请发送中断 */ ret = request_irq(TX_IRQ(port), gprs_uart_tx_chars, 0, portname, port); if (ret) { printk(KERN_ERR "cannot get irq %d\n", TX_IRQ(port)); rx_enabled(port) = 0; free_irq(RX_IRQ(port), port); goto err; } /* 设置串口为允许发送 */ tx_enabled(port) = 1; spin_unlock_irqrestore( port- lock, flags); return ret; /* 关闭串口,在关闭驱动的设备文件时会调用该函数,释放串口中断 */ static void gprs_uart_shutdown(struct uart_port *port) rx_enabled(port) = 0; /* 设置串口为不允许接收 */ free_irq(RX_IRQ(port), port); /* 释放接收中断 */ tx_enabled(port) = 0; /* 设置串口为不允许发送 */ free_irq(TX_IRQ(port), port); /* 释放发送中断 */ /* 设置串口参数 */ static void gprs_uart_set_termios(struct uart_port *port, struct ktermios *termios, struct ktermios *old) unsigned long flags; unsigned int baud, quot; unsigned int ulcon, ufcon = 0; /* 不支持moden控制信号线 * HUPCL: 关闭时挂断moden * CMSPAR: mark or space (stick) parity * CLOCAL: 忽略任何moden控制线 */ termios- c_cflag = ~(HUPCL | CMSPAR); termios- c_cflag |= CLOCAL; /* 获取用户设置的串口波特率,并计算分频数(串口波特率除数quot) */ baud = uart_get_baud_rate(port, termios, old, 0, 115200*8); if (baud == 38400 (port- flags UPF_SPD_MASK) == UPF_SPD_CUST) quot = port- custom_divisor; else quot = port- uartclk / baud / 16 - 1; /* 设置数据字长 */ switch (termios- c_cflag CSIZE) { case CS5: ulcon = S3C2410_LCON_CS5; break; case CS6: ulcon = S3C2410_LCON_CS6; break; case CS7: ulcon = S3C2410_LCON_CS7; break; case CS8: default: ulcon = S3C2410_LCON_CS8; break; } /* 是否要求设置两个停止位(CSTOPB) */ if (termios- c_cflag CSTOPB) ulcon |= S3C2410_LCON_STOPB; /* 是否使用奇偶检验 */ if (termios- c_cflag PARENB) { if (termios- c_cflag PARODD) /* 奇校验 */ ulcon |= S3C2410_LCON_PODD; else /* 偶校验 */ ulcon |= S3C2410_LCON_PEVEN; } else /* 无校验 */ { ulcon |= S3C2410_LCON_PNONE; } if (port- fifosize 1) ufcon |= S3C2410_UFCON_FIFOMODE | S3C2410_UFCON_RXTRIG8; spin_lock_irqsave( port- lock, flags); /* 设置FIFO控制寄存器、线控制寄存器和波特率除数寄存器 */ wr_regl(port, S3C2410_UFCON, ufcon); wr_regl(port, S3C2410_ULCON, ulcon); wr_regl(port, S3C2410_UBRDIV, quot); /* 更新串口FIFO的超时时限 */ uart_update_timeout(port, termios- c_cflag, baud); /* 设置我们感兴趣的Rx error */ port- read_status_mask = S3C2410_UERSTAT_OVERRUN; if (termios- c_iflag INPCK) port- read_status_mask |= S3C2410_UERSTAT_FRAME | S3C2410_UERSTAT_PARITY; /* 设置我们忽略的Rx error */ port- ignore_status_mask = 0; if (termios- c_iflag IGNPAR) port- ignore_status_mask |= S3C2410_UERSTAT_OVERRUN; if (termios- c_iflag IGNBRK termios- c_iflag IGNPAR) port- ignore_status_mask |= S3C2410_UERSTAT_FRAME; /* 若未设置CREAD(使用接收器),则忽略所有Rx error*/ if ((termios- c_cflag CREAD) == 0) port- ignore_status_mask |= RXSTAT_DUMMY_READ; spin_unlock_irqrestore( port- lock, flags); /* 获取串口类型 */ static const char *gprs_uart_type(struct uart_port *port) {/* 返回描述串口类型的字符串指针 */ return port- type == PORT_S3C2410 ? "gprs_uart:s3c2410_uart2" : NULL; /* 申请串口一些必要的资源,如IO端口/IO内存资源,必要时还可以重新映射串口端口 */ static int gprs_uart_request_port(struct uart_port *port) struct resource *res; const char *name = to_platform_device(port- dev)- name; /* request_mem_region请求分配IO内存,从开始port- mapbase,大小MAP_SIZE * port- mapbase保存当前串口的寄存器基地址(物理) * uart2: 0x50008000 */ res = request_mem_region(port- mapbase, MAP_SIZE, name); if (res == NULL) { printk(KERN_ERR"request_mem_region error: %p\n", res); return -EBUSY; } return 0; /* 释放串口已申请的IO端口/IO内存资源,必要时还需iounmap */ static void gprs_uart_release_port(struct uart_port *port) /* 释放已分配IO内存 */ release_mem_region(port- mapbase, MAP_SIZE); /* 执行串口所需的自动配置 */ static void gprs_uart_config_port(struct uart_port *port, int flags) { int retval; /* 请求串口 */ retval = gprs_uart_request_port(port); /* 设置串口类型 */ if (flags UART_CONFIG_TYPE retval == 0) port- type = PORT_S3C2410; /* The UART operations structure */ static struct uart_ops gprs_uart_ops = { .start_tx = gprs_uart_start_tx, /* Start transmitting */ .stop_tx = gprs_uart_stop_tx, /* Stop transmission */ .stop_rx = gprs_uart_stop_rx, /* Stop reception */ .enable_ms = gprs_uart_enable_ms, /* Enable modem status signals */ .tx_empty = gprs_uart_tx_empty, /* Transmitter busy? */ .get_mctrl = gprs_uart_get_mctrl, /* Get modem control */ .set_mctrl = gprs_uart_set_mctrl, /* Set modem control */ .break_ctl = gprs_uart_break_ctl, /* Set break signal */ .startup = gprs_uart_startup, /* App opens GPRS_UART */ .shutdown = gprs_uart_shutdown, /* App closes GPRS_UART */ .set_termios = gprs_uart_set_termios, /* Set termios */ .type = gprs_uart_type, /* Get UART type */ .request_port = gprs_uart_request_port, /* Claim resources associated with a GPRS_UART port */ .release_port = gprs_uart_release_port, /* Release resources associated with a GPRS_UART port */ .config_port = gprs_uart_config_port, /* Configure when driver adds a GPRS_UART port */ /* Uart driver for GPRS_UART */ static struct uart_driver gprs_uart_driver = { .owner = THIS_MODULE, /* Owner */ .driver_name = DEV_NAME, /* Driver name */ .dev_name = DEV_NAME, /* Device node name */ .major = GPRS_UART_MAJOR, /* Major number */ .minor = GPRS_UART_MINOR, /* Minor number start */ .nr = 1, /* Number of UART ports */ /* Uart port for GPRS_UART port */ static struct uart_port gprs_uart_port = { .irq = IRQ_S3CUART_RX2, /* IRQ */ .fifosize = GPRS_UART_FIFO_SIZE, /* Size of the FIFO */ .iotype = UPIO_MEM, /* IO memory */ .flags = UPF_BOOT_AUTOCONF, /* UART port flag */ .ops = gprs_uart_ops, /* UART operations */ .line = 0, /* UART port number */ .lock = __SPIN_LOCK_UNLOCKED(gprs_uart_port.lock), /* 初始化指定串口端口 */ static int gprs_uart_init_port(struct uart_port *port, struct platform_device *platdev) unsigned long flags; unsigned int gphcon; if (platdev == NULL) return -ENODEV; port- dev = platdev- /* 设置串口波特率时钟频率 */ port- uartclk = clk_get_rate(clk_get( platdev- dev, "pclk")); /* 设置串口的寄存器基地址(物理): 0x50008000 */ port- mapbase = S3C2410_PA_UART2; /* 设置当前串口的寄存器基地址(虚拟): 0xF5008000 */ port- membase = S3C24XX_VA_UART + (S3C2410_PA_UART2 - S3C24XX_PA_UART); spin_lock_irqsave( port- lock, flags); wr_regl(port, S3C2410_UCON, S3C2410_UCON_DEFAULT); wr_regl(port, S3C2410_ULCON, S3C2410_LCON_CS8 | S3C2410_LCON_PNONE); wr_regl(port, S3C2410_UFCON, S3C2410_UFCON_FIFOMODE | S3C2410_UFCON_RXTRIG8 | S3C2410_UFCON_RESETBOTH); /* 将I/O port H的gph6和gph7设置为TXD2和RXD2 */ gphcon = readl(S3C2410_GPHCON); gphcon = ~((0x5) 12); writel(gphcon, S3C2410_GPHCON); spin_unlock_irqrestore( port- lock, flags); return 0; /* Platform driver probe */ static int __init gprs_uart_probe(struct platform_device *dev) int ret; /* 初始化串口 */ ret = gprs_uart_init_port( gprs_uart_port, dev); if (ret 0) { printk(KERN_ERR"gprs_uart_probe: gprs_uart_init_port error: %d\n", ret); return ret; } /* 添加串口 */ ret = uart_add_one_port( gprs_uart_driver, gprs_uart_port); if (ret 0) { printk(KERN_ERR"gprs_uart_probe: uart_add_one_port error: %d\n", ret); return ret; } /* 将串口uart_port结构体保存在platform_device- dev- driver_data中 */ platform_set_drvdata(dev, gprs_uart_port); return 0; /* Called when the platform driver is unregistered */ static int gprs_uart_remove(struct platform_device *dev) platform_set_drvdata(dev, NULL); /* 移除串口 */ uart_remove_one_port( gprs_uart_driver, gprs_uart_port); return 0; /* Suspend power management event */ static int gprs_uart_suspend(struct platform_device *dev, pm_message_t state) uart_suspend_port( gprs_uart_driver, gprs_uart_port); return 0; /* Resume after a previous suspend */ static int gprs_uart_resume(struct platform_device *dev) uart_resume_port( gprs_uart_driver, gprs_uart_port); return 0; /* Platform driver for GPRS_UART */ static struct platform_driver gprs_plat_driver = { .probe = gprs_uart_probe, /* Probe method */ .remove = __exit_p(gprs_uart_remove), /* Detach method */ .suspend = gprs_uart_suspend, /* Power suspend */ .resume = gprs_uart_resume, /* Resume after a suspend */ .driver = { .owner = THIS_MODULE, .name = DEV_NAME, /* Driver name */ }, /* Platform device for GPRS_UART */ struct platform_device *gprs_plat_device; static int __init gprs_init_module(void) int retval; /* Register uart_driver for GPRS_UART */ retval = uart_register_driver( gprs_uart_driver); if (0 != retval) { printk(KERN_ERR "gprs_init_module: cant register the GPRS_UART driver %d\n",retval); return retval; } /* Register platform device for GPRS_UART. Usually called during architecture-specific setup */ gprs_plat_device = platform_device_register_simple(DEV_NAME, 0, NULL, 0); if (IS_ERR(gprs_plat_device)) { retval = PTR_ERR(gprs_plat_device); printk(KERN_ERR "gprs_init_module: cant register platform device %d\n", retval); goto fail_reg_plat_dev; } /* Announce a matching driver for the platform devices registered above */ retval = platform_driver_register( gprs_plat_driver); if (0 != retval) { printk(KERN_ERR "gprs_init_module: cant register platform driver %d\n", retval); goto fail_reg_plat_drv; } return 0; /* succeed */ fail_reg_plat_drv: platform_device_unregister(gprs_plat_device); fail_reg_plat_dev: uart_unregister_driver( gprs_uart_driver); return retval; static void __exit gprs_exit_module(void) /* The order of unregistration is important. Unregistering the UART driver before the platform driver will crash the system */ /* Unregister the platform driver */ platform_driver_unregister( gprs_plat_driver); /* Unregister the platform devices */ platform_device_unregister(gprs_plat_device); /* Unregister the GPRS_UART driver */ uart_unregister_driver( gprs_uart_driver); module_init(gprs_init_module); module_exit(gprs_exit_module); MODULE_AUTHOR("lingd"); MODULE_LICENSE("Dual BSD/GPL");
zynq操作系统: Linux驱动开发串口篇 串口( UART)是一种非常常见的外设, 串口在嵌入式开发领域当中一般作为一种调试手段,通过串口将调试信息打印出来,或者通过串口发送指令给主机端进行处理;当然除了作为基本的调试手段之外,还可以通过串口与其他设备或传感器进行通信, 譬如有些 sensor 就使用了串口通信的方式与主机端进行数据交互。
Linux串口驱动程序(3)-打开设备 Linux串口驱动程序(3)-打开设备先来分析一下串口打开的过程: 1、用户调用open函数打开串口设备文件;2、在内核中通过tty子系统,把open操作层层传递到串口驱动程序中;3、在串口驱动程序中的xx_open最终实现这个操作。
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