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i.MX 6ULL 驱动开发 二十三：UART
一、UART 协议
二、UART 和 TTY 关系
基于Linux的tty架构及UART驱动详解 - 一口Linux - 博客园 (cnblogs.com)
三、Linux UART 驱动框架中重要对象
1、UART 驱动
struct uart_driver { struct module *owner; const char *driver_name; const char *dev_name; int major; int minor; int nr; struct console *cons; /* * 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; };- 1
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每个串口驱动都需要定义一个
uart_driver，加载驱动时向系统注册这个uart_driver，注销驱动时注销掉注册的uart_driver。2、UART 控制器
struct uart_port { spinlock_t lock; /* port lock */ unsigned long iobase; /* in/out[bwl] */ unsigned char __iomem *membase; /* read/write[bwl] */ unsigned int (*serial_in)(struct uart_port *, int); void (*serial_out)(struct uart_port *, int, int); void (*set_termios)(struct uart_port *, struct ktermios *new, struct ktermios *old); void (*set_mctrl)(struct uart_port *, unsigned int); int (*startup)(struct uart_port *port); void (*shutdown)(struct uart_port *port); void (*throttle)(struct uart_port *port); void (*unthrottle)(struct uart_port *port); int (*handle_irq)(struct uart_port *); void (*pm)(struct uart_port *, unsigned int state, unsigned int old); void (*handle_break)(struct uart_port *); int (*rs485_config)(struct uart_port *, struct serial_rs485 *rs485); unsigned int irq; /* irq number */ unsigned long irqflags; /* irq flags */ unsigned int uartclk; /* base uart clock */ unsigned int fifosize; /* tx fifo size */ unsigned char x_char; /* xon/xoff char */ unsigned char regshift; /* reg offset shift */ unsigned char iotype; /* io access style */ unsigned char unused1; #define UPIO_PORT (SERIAL_IO_PORT) /* 8b I/O port access */ #define UPIO_HUB6 (SERIAL_IO_HUB6) /* Hub6 ISA card */ #define UPIO_MEM (SERIAL_IO_MEM) /* 8b MMIO access */ #define UPIO_MEM32 (SERIAL_IO_MEM32) /* 32b little endian */ #define UPIO_AU (SERIAL_IO_AU) /* Au1x00 and RT288x type IO */ #define UPIO_TSI (SERIAL_IO_TSI) /* Tsi108/109 type IO */ #define UPIO_MEM32BE (SERIAL_IO_MEM32BE) /* 32b big endian */ unsigned int read_status_mask; /* driver specific */ unsigned int ignore_status_mask; /* driver specific */ struct uart_state *state; /* pointer to parent state */ struct uart_icount icount; /* statistics */ struct console *cons; /* struct console, if any */ #if defined(CONFIG_SERIAL_CORE_CONSOLE) || defined(SUPPORT_SYSRQ) unsigned long sysrq; /* sysrq timeout */ #endif /* flags must be updated while holding port mutex */ upf_t flags; /* * These flags must be equivalent to the flags defined in * include/uapi/linux/tty_flags.h which are the userspace definitions * assigned from the serial_struct flags in uart_set_info() * [for bit definitions in the UPF_CHANGE_MASK] * * Bits [0..UPF_LAST_USER] are userspace defined/visible/changeable * except bit 15 (UPF_NO_TXEN_TEST) which is masked off. * The remaining bits are serial-core specific and not modifiable by * userspace. */ #define UPF_FOURPORT ((__force upf_t) ASYNC_FOURPORT /* 1 */ ) #define UPF_SAK ((__force upf_t) ASYNC_SAK /* 2 */ ) #define UPF_SPD_HI ((__force upf_t) ASYNC_SPD_HI /* 4 */ ) #define UPF_SPD_VHI ((__force upf_t) ASYNC_SPD_VHI /* 5 */ ) #define UPF_SPD_CUST ((__force upf_t) ASYNC_SPD_CUST /* 0x0030 */ ) #define UPF_SPD_WARP ((__force upf_t) ASYNC_SPD_WARP /* 0x1010 */ ) #define UPF_SPD_MASK ((__force upf_t) ASYNC_SPD_MASK /* 0x1030 */ ) #define UPF_SKIP_TEST ((__force upf_t) ASYNC_SKIP_TEST /* 6 */ ) #define UPF_AUTO_IRQ ((__force upf_t) ASYNC_AUTO_IRQ /* 7 */ ) #define UPF_HARDPPS_CD ((__force upf_t) ASYNC_HARDPPS_CD /* 11 */ ) #define UPF_SPD_SHI ((__force upf_t) ASYNC_SPD_SHI /* 12 */ ) #define UPF_LOW_LATENCY ((__force upf_t) ASYNC_LOW_LATENCY /* 13 */ ) #define UPF_BUGGY_UART ((__force upf_t) ASYNC_BUGGY_UART /* 14 */ ) #define UPF_NO_TXEN_TEST ((__force upf_t) (1 << 15)) #define UPF_MAGIC_MULTIPLIER ((__force upf_t) ASYNC_MAGIC_MULTIPLIER /* 16 */ ) /* Port has hardware-assisted h/w flow control */ #define UPF_AUTO_CTS ((__force upf_t) (1 << 20)) #define UPF_AUTO_RTS ((__force upf_t) (1 << 21)) #define UPF_HARD_FLOW ((__force upf_t) (UPF_AUTO_CTS | UPF_AUTO_RTS)) /* Port has hardware-assisted s/w flow control */ #define UPF_SOFT_FLOW ((__force upf_t) (1 << 22)) #define UPF_CONS_FLOW ((__force upf_t) (1 << 23)) #define UPF_SHARE_IRQ ((__force upf_t) (1 << 24)) #define UPF_EXAR_EFR ((__force upf_t) (1 << 25)) #define UPF_BUG_THRE ((__force upf_t) (1 << 26)) /* The exact UART type is known and should not be probed. */ #define UPF_FIXED_TYPE ((__force upf_t) (1 << 27)) #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 0x17fff #define UPF_CHANGE_MASK ((__force upf_t) __UPF_CHANGE_MASK) #define UPF_USR_MASK ((__force upf_t) (UPF_SPD_MASK|UPF_LOW_LATENCY)) #if __UPF_CHANGE_MASK > ASYNC_FLAGS #error Change mask not equivalent to userspace-visible bit defines #endif /* * Must hold termios_rwsem, port mutex and port lock to change; * can hold any one lock to read. */ upstat_t status; #define UPSTAT_CTS_ENABLE ((__force upstat_t) (1 << 0)) #define UPSTAT_DCD_ENABLE ((__force upstat_t) (1 << 1)) #define UPSTAT_AUTORTS ((__force upstat_t) (1 << 2)) #define UPSTAT_AUTOCTS ((__force upstat_t) (1 << 3)) #define UPSTAT_AUTOXOFF ((__force upstat_t) (1 << 4)) int hw_stopped; /* sw-assisted CTS flow state */ unsigned int mctrl; /* current modem ctrl settings */ unsigned int timeout; /* character-based timeout */ unsigned int type; /* port type */ const struct uart_ops *ops; unsigned int custom_divisor; unsigned int line; /* port index */ unsigned int minor; resource_size_t mapbase; /* for ioremap */ resource_size_t mapsize; struct device *dev; /* parent device */ unsigned char hub6; /* this should be in the 8250 driver */ unsigned char suspended; unsigned char irq_wake; unsigned char unused[2]; struct attribute_group *attr_group; /* port specific attributes */ const struct attribute_group **tty_groups; /* all attributes (serial core use only) */ struct serial_rs485 rs485; void *private_data; /* generic platform data pointer */ };- 1
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Linux中使用struct uart_port描述硬件信息。3、UART 操作集
/* * This structure describes all the operations that can be done on the * physical hardware. See Documentation/serial/driver for details. */ struct uart_ops { unsigned int (*tx_empty)(struct uart_port *); void (*set_mctrl)(struct uart_port *, unsigned int mctrl); unsigned int (*get_mctrl)(struct uart_port *); void (*stop_tx)(struct uart_port *); void (*start_tx)(struct uart_port *); void (*throttle)(struct uart_port *); void (*unthrottle)(struct uart_port *); void (*send_xchar)(struct uart_port *, char ch); void (*stop_rx)(struct uart_port *); void (*enable_ms)(struct uart_port *); void (*break_ctl)(struct uart_port *, int ctl); int (*startup)(struct uart_port *); void (*shutdown)(struct uart_port *); void (*flush_buffer)(struct uart_port *); void (*set_termios)(struct uart_port *, struct ktermios *new, struct ktermios *old); void (*set_ldisc)(struct uart_port *, struct ktermios *); void (*pm)(struct uart_port *, unsigned int state, unsigned int oldstate); /* * Return a string describing the type of the port */ const char *(*type)(struct uart_port *); /* * Release IO and memory resources used by the port. * This includes iounmap if necessary. */ void (*release_port)(struct uart_port *); /* * Request IO and memory resources used by the port. * This includes iomapping the port if necessary. */ int (*request_port)(struct uart_port *); void (*config_port)(struct uart_port *, int); int (*verify_port)(struct uart_port *, struct serial_struct *); int (*ioctl)(struct uart_port *, unsigned int, unsigned long); #ifdef CONFIG_CONSOLE_POLL int (*poll_init)(struct uart_port *); void (*poll_put_char)(struct uart_port *, unsigned char); int (*poll_get_char)(struct uart_port *); #endif };- 1
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四、UART 驱动编写思路
Linux下UART一般都编写好，根据设备树找到相关驱动分析即可。五、imx6ull 下 UART 驱动分析
文档路径：
drivers\tty\serial\imx.c。1、驱动框架
static struct uart_driver imx_reg = { .owner = THIS_MODULE, .driver_name = DRIVER_NAME, .dev_name = DEV_NAME, .major = SERIAL_IMX_MAJOR, .minor = MINOR_START, .nr = ARRAY_SIZE(imx_ports), // imx_ports 封装 struct uart_port .cons = IMX_CONSOLE, }; static struct platform_driver serial_imx_driver = { .probe = serial_imx_probe, .remove = serial_imx_remove, .suspend = serial_imx_suspend, .resume = serial_imx_resume, .id_table = imx_uart_devtype, .driver = { .name = "imx-uart", .of_match_table = imx_uart_dt_ids, }, }; static int __init imx_serial_init(void) { int ret = uart_register_driver(&imx_reg); if (ret) return ret; ret = platform_driver_register(&serial_imx_driver); if (ret != 0) uart_unregister_driver(&imx_reg); return ret; } static void __exit imx_serial_exit(void) { platform_driver_unregister(&serial_imx_driver); uart_unregister_driver(&imx_reg); }- 1
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1、
UART驱动使用platform驱动框架。2、在加载驱动时注册
UART驱动。2、初始化
见
serial_imx_probe函数。3、注销
见
serial_imx_remove函数。六、添加设备树
1、UART 设备树相关说明
见文档：
Documentation\devicetree\bindings\serial\fsl-imx-uart.txt。2、确定使用 UART
通过原理图可以确定，使用接口为
uart3。3、添加 pinctrl 子系统相关配置
pinctrl_uart3: uart3grp { fsl,pins = < MX6UL_PAD_UART3_TX_DATA__UART3_DCE_TX 0X1b0b1 MX6UL_PAD_UART3_RX_DATA__UART3_DCE_RX 0X1b0b1 >; };- 1
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4、在 uart3 下追加配置
&uart3 { pinctrl-names = "default"; pinctrl-0 = <&pinctrl_uart3>; status = "okay"; };- 1
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5、编译设备树
onlylove@ubuntu:~/my/linux/linux-imx-4.1.15$ make dtbs CHK include/config/kernel.release CHK include/generated/uapi/linux/version.h CHK include/generated/utsrelease.h make[1]: 'include/generated/mach-types.h' is up to date. CHK include/generated/bounds.h CHK include/generated/asm-offsets.h CALL scripts/checksyscalls.sh DTC arch/arm/boot/dts/imx6ull-alientek-emmc.dtb DTC arch/arm/boot/dts/imx6ull-alientek-nand.dtb onlylove@ubuntu:~/my/linux/linux-imx-4.1.15$- 1
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6、测试
# pwd /proc/device-tree/soc/aips-bus@02100000 # ls #address-cells lcdif@021c8000 serial@021f0000 #size-cells mmdc@021b0000 serial@021f4000 adc@02198000 name serial@021fc000 compatible ocotp-ctrl@021bc000 usb@02184000 csi@021c4000 pxp@021cc000 usb@02184200 csu@021c0000 qspi@021e0000 usbmisc@02184800 ethernet@02188000 ranges usdhc@02190000 i2c@021a0000 reg usdhc@02194000 i2c@021a4000 romcp@021ac000 weim@021b8000 i2c@021a8000 serial@021e8000 i2c@021f8000 serial@021ec000 # cd serial@021ec000/ # ls clock-names dma-names name reg clocks dmas pinctrl-0 status compatible interrupts pinctrl-names # cat compatible fsl,imx6ul-uartfsl,imx6q-uartfsl,imx21-uart# #- 1
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七、驱动编写
uart相关驱动Linux内核已添加，不需要我们编写。
# ls /dev/ttymxc* -l crw------- 1 root root 207, 16 Jan 1 05:59 /dev/ttymxc0 crw-rw---- 1 root root 207, 18 Jan 1 00:00 /dev/ttymxc2 #- 1
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通过以上消息，
uart3驱动加载成功，uart3在应用层映射为ttymxc2。八、应用编写
1、概述
在
Linux下UART驱动和tty关系密切，在应用层使用UART是需特别注意，否则一些特殊字符传输可能有问题。2、程序
/*************************************************************** Copyright © ALIENTEK Co., Ltd. 1998-2021. All rights reserved. 文件名 : uart_test.c 作者 : 邓涛 版本 : V1.0 描述 : 串口在原始模式下进行数据传输--应用程序示例代码 其他 : 无 论坛 : www.openedv.com 日志 : 初版 V1.0 2021/7/20 邓涛创建 ***************************************************************/ #define _GNU_SOURCE //在源文件开头定义_GNU_SOURCE宏 #include#include #include #include #include #include #include #include #include #include #include typedef struct uart_hardware_cfg { unsigned int baudrate; /* 波特率 */ unsigned char dbit; /* 数据位 */ char parity; /* 奇偶校验 */ unsigned char sbit; /* 停止位 */ } uart_cfg_t; static struct termios old_cfg; //用于保存终端的配置参数 static int fd; //串口终端对应的文件描述符 /** ** 串口初始化操作 ** 参数device表示串口终端的设备节点 **/ static int uart_init(const char *device) { /* 打开串口终端 */ fd = open(device, O_RDWR | O_NOCTTY); if (0 > fd) { fprintf(stderr, "open error: %s: %s\n", device, strerror(errno)); return -1; } /* 获取串口当前的配置参数 */ if (0 > tcgetattr(fd, &old_cfg)) { fprintf(stderr, "tcgetattr error: %s\n", strerror(errno)); close(fd); return -1; } return 0; } /** ** 串口配置 ** 参数cfg指向一个uart_cfg_t结构体对象 **/ static int uart_cfg(const uart_cfg_t *cfg) { struct termios new_cfg = {0}; //将new_cfg对象清零 speed_t speed; /* 设置为原始模式 */ cfmakeraw(&new_cfg); /* 使能接收 */ new_cfg.c_cflag |= CREAD; /* 设置波特率 */ switch (cfg->baudrate) { case 1200: speed = B1200; break; case 1800: speed = B1800; break; case 2400: speed = B2400; break; case 4800: speed = B4800; break; case 9600: speed = B9600; break; case 19200: speed = B19200; break; case 38400: speed = B38400; break; case 57600: speed = B57600; break; case 115200: speed = B115200; break; case 230400: speed = B230400; break; case 460800: speed = B460800; break; case 500000: speed = B500000; break; default: //默认配置为115200 speed = B115200; printf("default baud rate: 115200\n"); break; } if (0 > cfsetspeed(&new_cfg, speed)) { fprintf(stderr, "cfsetspeed error: %s\n", strerror(errno)); return -1; } /* 设置数据位大小 */ new_cfg.c_cflag &= ~CSIZE; //将数据位相关的比特位清零 switch (cfg->dbit) { case 5: new_cfg.c_cflag |= CS5; break; case 6: new_cfg.c_cflag |= CS6; break; case 7: new_cfg.c_cflag |= CS7; break; case 8: new_cfg.c_cflag |= CS8; break; default: //默认数据位大小为8 new_cfg.c_cflag |= CS8; printf("default data bit size: 8\n"); break; } /* 设置奇偶校验 */ switch (cfg->parity) { case 'N': //无校验 new_cfg.c_cflag &= ~PARENB; new_cfg.c_iflag &= ~INPCK; break; case 'O': //奇校验 new_cfg.c_cflag |= (PARODD | PARENB); new_cfg.c_iflag |= INPCK; break; case 'E': //偶校验 new_cfg.c_cflag |= PARENB; new_cfg.c_cflag &= ~PARODD; /* 清除PARODD标志，配置为偶校验 */ new_cfg.c_iflag |= INPCK; break; default: //默认配置为无校验 new_cfg.c_cflag &= ~PARENB; new_cfg.c_iflag &= ~INPCK; printf("default parity: N\n"); break; } /* 设置停止位 */ switch (cfg->sbit) { case 1: //1个停止位 new_cfg.c_cflag &= ~CSTOPB; break; case 2: //2个停止位 new_cfg.c_cflag |= CSTOPB; break; default: //默认配置为1个停止位 new_cfg.c_cflag &= ~CSTOPB; printf("default stop bit size: 1\n"); break; } /* 将MIN和TIME设置为0 */ new_cfg.c_cc[VTIME] = 0; new_cfg.c_cc[VMIN] = 0; /* 清空缓冲区 */ if (0 > tcflush(fd, TCIOFLUSH)) { fprintf(stderr, "tcflush error: %s\n", strerror(errno)); return -1; } /* 写入配置、使配置生效 */ if (0 > tcsetattr(fd, TCSANOW, &new_cfg)) { fprintf(stderr, "tcsetattr error: %s\n", strerror(errno)); return -1; } /* 配置OK 退出 */ return 0; } /*** --dev=/dev/ttymxc2 --brate=115200 --dbit=8 --parity=N --sbit=1 --type=read ***/ /** ** 打印帮助信息 **/ static void show_help(const char *app) { printf("Usage: %s [选项]\n" "\n必选选项:\n" " --dev=DEVICE 指定串口终端设备名称, 譬如--dev=/dev/ttymxc2\n" " --type=TYPE 指定操作类型, 读串口还是写串口, 譬如--type=read(read表示读、write表示写、其它值无效)\n" "\n可选选项:\n" " --brate=SPEED 指定串口波特率, 譬如--brate=115200\n" " --dbit=SIZE 指定串口数据位个数, 譬如--dbit=8(可取值为: 5/6/7/8)\n" " --parity=PARITY 指定串口奇偶校验方式, 譬如--parity=N(N表示无校验、O表示奇校验、E表示偶校验)\n" " --sbit=SIZE 指定串口停止位个数, 譬如--sbit=1(可取值为: 1/2)\n" " --help 查看本程序使用帮助信息\n\n", app); } /** ** 信号处理函数，当串口有数据可读时，会跳转到该函数执行 **/ static void io_handler(int sig, siginfo_t *info, void *context) { unsigned char buf[10] = {0}; int ret; int n; if(SIGRTMIN != sig) return; /* 判断串口是否有数据可读 */ if (POLL_IN == info->si_code) { ret = read(fd, buf, 8); //一次最多读8个字节数据 printf("[ "); for (n = 0; n < ret; n++) printf("0x%hhx ", buf[n]); printf("]\n"); } } /** ** 异步I/O初始化函数 **/ static void async_io_init(void) { struct sigaction sigatn; int flag; /* 使能异步I/O */ flag = fcntl(fd, F_GETFL); //使能串口的异步I/O功能 flag |= O_ASYNC; fcntl(fd, F_SETFL, flag); /* 设置异步I/O的所有者 */ fcntl(fd, F_SETOWN, getpid()); /* 指定实时信号SIGRTMIN作为异步I/O通知信号 */ fcntl(fd, F_SETSIG, SIGRTMIN); /* 为实时信号SIGRTMIN注册信号处理函数 */ sigatn.sa_sigaction = io_handler; //当串口有数据可读时，会跳转到io_handler函数 sigatn.sa_flags = SA_SIGINFO; sigemptyset(&sigatn.sa_mask); sigaction(SIGRTMIN, &sigatn, NULL); } int main(int argc, char *argv[]) { uart_cfg_t cfg = {0}; char *device = NULL; int rw_flag = -1; unsigned char w_buf[10] = {0x11, 0x22, 0x33, 0x44,0x55, 0x66, 0x77, 0x88}; //通过串口发送出去的数据 int n; /* 解析出参数 */ for (n = 1; n < argc; n++) { if (!strncmp("--dev=", argv[n], 6)) device = &argv[n][6]; else if (!strncmp("--brate=", argv[n], 8)) cfg.baudrate = atoi(&argv[n][8]); else if (!strncmp("--dbit=", argv[n], 7)) cfg.dbit = atoi(&argv[n][7]); else if (!strncmp("--parity=", argv[n], 9)) cfg.parity = argv[n][9]; else if (!strncmp("--sbit=", argv[n], 7)) cfg.sbit = atoi(&argv[n][7]); else if (!strncmp("--type=", argv[n], 7)) { if (!strcmp("read", &argv[n][7])) rw_flag = 0; //读 else if (!strcmp("write", &argv[n][7])) rw_flag = 1; //写 } else if (!strcmp("--help", argv[n])) { show_help(argv[0]); //打印帮助信息 exit(EXIT_SUCCESS); } } if (NULL == device || -1 == rw_flag) { fprintf(stderr, "Error: the device and read|write type must be set!\n"); show_help(argv[0]); exit(EXIT_FAILURE); } /* 串口初始化 */ if (uart_init(device)) exit(EXIT_FAILURE); /* 串口配置 */ if (uart_cfg(&cfg)) { tcsetattr(fd, TCSANOW, &old_cfg); //恢复到之前的配置 close(fd); exit(EXIT_FAILURE); } /* 读|写串口 */ switch (rw_flag) { case 0: //读串口数据 async_io_init(); //我们使用异步I/O方式读取串口的数据，调用该函数去初始化串口的异步I/O for ( ; ; ) sleep(1); //进入休眠、等待有数据可读，有数据可读之后就会跳转到io_handler()函数 break; case 1: //向串口写入数据 for ( ; ; ) { //循环向串口写入数据 write(fd, w_buf, 8); //一次向串口写入8个字节 sleep(1); //间隔1秒钟 } break; } /* 退出 */ tcsetattr(fd, TCSANOW, &old_cfg); //恢复到之前的配置 close(fd); exit(EXIT_SUCCESS); } - 1
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程序使用正点原子提供。
九、测试
1、数据接收
# ./uart_app --dev=/dev/ttymxc2 --type=read default baud rate: 115200 default data bit size: 8 default parity: N default stop bit size: 1 [ 0x11 0x22 0x33 0x44 0x55 0x66 0x77 0x88 ] [ 0x11 0x22 0x33 0x44 0x55 0x66 0x77 0x88 ] [ 0x11 0x22 0x33 0x44 0x55 0x66 0x77 0x88 ] [ 0x11 0x22 0x33 0x44 0x55 0x66 0x77 0x88 ] [ 0x11 0x22 0x33 0x44 0x55 0x66 0x77 0x88 ] [ 0x11 0x22 0x33 0x44 0x55 0x66 0x77 0x88 ] [ 0x11 0x22 0x33 0x44 0x55 0x66 0x77 0x88 ] [ 0x11 0x22 0x33 0x44 0x55 0x66 0x77 0x88 ] #- 1
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2、数据发送
-
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- 原文地址：https://blog.csdn.net/OnlyLove_/article/details/127950130
