前言

一. 功能特點

RockchipUART (Universal Asynchronous Receiver/Transmitter) 基于16550A串口標準，完整模塊支持以下功能：

二、代碼位置

在Linuxkernel 中，使用8250串口通用驅動，以下為主要驅動文件：

(資料圖片僅供參考)

drivers/tty/serial/8250/8250_core.c # 8250串口驅動核心

drivers/tty/serial/8250/8250_dw.c # Synopsis DesignWare 8250串口驅動

drivers/tty/serial/8250/8250_dma.c # 8250串口DMA驅動

drivers/tty/serial/8250/8250_port.c # 8250串口端口操作

drivers/tty/serial/8250/8250_early.c # 8250串口early console驅動

SDK中提供的UART默認配置已經使用了8250驅動我們就不需要修改

三、硬件原理圖

串口功能的硬件上比較簡單，這是只附上調試串口的原理圖

四、設備樹配置

rk平臺的設備樹修改路徑都是在kernel\\arch\\arm64\\boot\\dts\\rockchip下面，具體哪個文件根據對應開發板來決定，通常描述設備硬件配置在rkxxxx.dtsi中，比如在rk3588s.dtsi中：

uart2: serial@feb50000 {compatible = "rockchip,rk3588-uart", "snps,dw-apb-uart";reg = < 0x0 0xfeb50000 0x0 0x100 >;interrupts = < GIC_SPI 333 IRQ_TYPE_LEVEL_HIGH >;clocks = < &cru SCLK_UART2 >, < &cru PCLK_UART2 >;clock-names = "baudclk", "apb_pclk";reg-shift = < 2 >;reg-io-width = < 4 >;dmas = < &dmac0 10 >, < &dmac0 11 >;pinctrl-names = "default";pinctrl-0 = < &uart2m1_xfer >;status = "disabled";};

4.1作為普通串口

假入我們想使用w3開發板上40PIN上的uart7

我們在dts可以使用如下配置打開

&uart7 {status = "okay";pinctrl-names = "default";pinctrl-0 = < &uart7m1_xfer >;};

4.2作為調試串口

Rockchip UART作為控制臺，使用fiq_debugger流程。

在dts中fiq_debugger節點配置如下。由于fiq_debugger和普通串口互斥，在使能fiq_debugger節點后必須禁用對應的普通串口uart節點。

chosen: chosen {bootargs = "earlycon=uart8250,mmio32,0xfe660000 console=ttyFIQ0";};fiq-debugger {compatible = "rockchip,fiq-debugger";rockchip,serial-id = < 2 >;rockchip,wake-irq = < 0 >;/* If enable uart uses irq insteadof fiq */rockchip,irq-mode-enable = < 1 >;rockchip,baudrate = < 1500000 >; /* Only 115200 and 1500000 */interrupts = < GIC_SPI 252 IRQ_TYPE_LEVEL_LOW >;pinctrl-names = "default";pinctrl-0 = < &uart2m0_xfer >;status = "okay";};&uart2 {status = "disabled";};

五、串口相關問題

5.1設備注冊

普通串口設備將會根據dts中的aliase來對串口進行編號，對應注冊成ttySx設備。注冊的節點為/dev/ttyS4，命名規則是通過dts中的aliases來的。

aliases {serial0 = &uart0;serial1 = &uart1;serial2 = &uart2;serial3 = &uart3;}

對應uart0注冊為ttyS0，uart0注冊為ttyS1，如果需要把uart3注冊成ttyS1，可以進行以下修改

serial1 = &uart3;  serial3 = &uart1;

5.2控制臺打印相關

Rockchip UART打印通常包括DDR階段、Miniloader階段、TF-A (Trusted Firmware-A)階段、OP-TEE階段、Uboot階段和Kernel階段，我們平時主要關注的是uboot階段和kernel階段的打印，在這兩個階段我們可以嘗試關閉所有打印或切換所有打印到其他UART，RK平臺默認的調試串口是uart2_m0這一組引腳，假如現在我將打印換成其他串口，可以嘗試以下做法。

5.2.1DDR Loader修改方法

DDR Loader中關閉或切換打印，需要修改DDR Loader中的UART打印配置，修改文件rkbin/tools/ddrbin_param.txt中的以下參數：

uart id= # UART控制器id，配置為0xf為關閉打印

uart iomux= # 復用的IOMUX引腳 uart

baudrate= # 115200 or 1500000

修改完成后，使用以下命令重新生成ddr.bin固件。

./ddrbin_tool ddrbin_param.txt rk3588_ddr_lp4_2112MHz_lp5_2736MHz_v1.09.bin

5.2.2Uboot修改方法

Uboot中關閉打印，需要在menuconfig中，打開配CONFIG_DISABLE_CONSOLE，保存到.config文件

Uboot中切換打印，由傳參機制決定，不需要進行額外修改。uboot解析傳參機制相關代碼在arch/arm/mach-rockchip/board.c的board_init_f_init_serial()函數中。

5.2.3kernel修改方法

去掉打印需要在menuconfig中，關閉配置CONFIG_SERIAL_8250_CONSOLE。

Device Drivers --->

Character devices --->

Serial drivers --->

[ ]Console on 8250/16550 and compatible serial port

在dts配置中找到類似以下內容，并去掉UART基地址和console相關配置參數

chosen: chosen {bootargs = "earlycon=uart8250,mmio32,0xfeb50000 console=ttyFIQ0 irqchip.gicv3_pseudo_nmi=0 root=PARTUUID=614e0000-0000 rw rootwait";};

將0xfeb50000 console=ttyFIQ0 去掉，然后找到fiq-debugger節點，修改serial-id為0xffffffff，去掉UART引腳復用相關配置。注意，需要保持fiqdebugger節點使能，保持fiq-debugger流程系統才能正常啟動

fiq_debugger: fiq-debugger {compatible = "rockchip,fiq-debugger";rockchip,serial-id = < 0xffffffff >;rockchip,wake-irq = < 0 >;/* If enable uart uses irq instead of fiq */rockchip,irq-mode-enable = < 1 >;rockchip,baudrate = < 1500000 >;  /* Only 115200 and 1500000 */interrupts = < GIC_SPI 423 IRQ_TYPE_LEVEL_LOW >;status = "okay";};

切換打印串口例如將Kernel打印從UART2切換到UART3，在dts配置中找到類似以下內容，將UART基地址由UART2改為UART3.

bootargs = "earlycon=uart8250,mmio32,0xfe670000 console=ttyFIQ0";

0xfe670000是UART3基地址，然后找到fiq-debugger節點，修改serial-id為3，修改UART3引腳復用配置pinctrl-0 = <&uart3m0_xfer>。注意，同時需要將切換為打印串口的UART3作為普通串口的節點禁用。

六、串口測試

在開發板上跑一套應用程序，可以發送數據，可以接收數據，測試方法可以短接TX_RX

#include < stdio.h >#include < stdlib.h >#include < errno.h >#include < unistd.h >#include < fcntl.h >#include < string.h >#include < termio.h >#include < time.h >#include < pthread.h >int read_data(int fd, void *buf, int len);int write_data(int fd, void *buf, int len);int setup_port(int fd, int baud, int databits, int parity, int stopbits);void print_usage(char *program_name);pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;pthread_cond_t data_ready = PTHREAD_COND_INITIALIZER;int data_available = 0;void *read_thread(void *arg) {    int fd = *(int *)arg;    char buffer[1024]; // 存儲讀取的數據    while (1) {        int bytes_read = read_data(fd, buffer, sizeof(buffer));        if (bytes_read > 0) {            printf("Read Thread: Read %d bytes: %s\\n", bytes_read, buffer);        } else {            // 處理讀取錯誤或設備關閉的情況            break;        }    }        pthread_exit(NULL);}void *write_thread(void *arg) {    int fd = *(int *)arg;char input[1024]; // 存儲用戶輸入的數據    while (1) {        printf("Enter data to write (or "q" to quit): ");        fgets(input, sizeof(input), stdin);        if (strcmp(input, "q\\n") == 0 || strcmp(input, "Q\\n") == 0) {            // 用戶輸入 "q" 或 "Q"，退出循環            break;        }        int len = strlen(input);        int bytes_written = write_data(fd, input, len);        if (bytes_written > 0) {            printf("Write Thread: Wrote %d bytes: %s\\n", bytes_written, input);        }    }        pthread_exit(NULL);}int main(int argc, char *argv[]) //./a.out /dev/ttyS4 115200 8 0 1{    int fd;    int baud;    int len;    int count;    int i;    int databits;    int stopbits;    int parity;    if (argc != 6) {        print_usage(argv[0]);        return 1;    }     baud = atoi(argv[2]);    if ((baud < 0) || (baud > 921600)) {        fprintf(stderr, "Invalid baudrate!\\n");        return 1;    }     databits = atoi(argv[3]);    if ((databits < 5) || (databits > 8)) {        fprintf(stderr, "Invalid databits!\\n");        return 1;    }     parity = atoi(argv[4]);    if ((parity < 0) || (parity > 2)) {        fprintf(stderr, "Invalid parity!\\n");        return 1;    }     stopbits = atoi(argv[5]);    if ((stopbits < 1) || (stopbits > 2)) {        fprintf(stderr, "Invalid stopbits!\\n");        return 1;    }      fd = open(argv[1], O_RDWR, 0);    if (fd < 0) {        fprintf(stderr, "open < %s > error %s\\n", argv[1], strerror(errno));        return 1;    }     if (setup_port(fd, baud, databits, parity, stopbits)) {        fprintf(stderr, "setup_port error %s\\n", strerror(errno));        close(fd);        return 1;    }pthread_t read_tid, write_tid;    int ret;    // 創建讀取線程    ret = pthread_create(&read_tid, NULL, read_thread, &fd);    if (ret != 0) {        fprintf(stderr, "Failed to create read thread\\n");        return 1;    }    // 創建寫入線程    ret = pthread_create(&write_tid, NULL, write_thread, &fd);    if (ret != 0) {        fprintf(stderr, "Failed to create write thread\\n");        return 1;    }    // 等待讀取線程和寫入線程結束    pthread_join(read_tid, NULL);    pthread_join(write_tid, NULL);    close(fd);     return 0;}static int baudflag_arr[] = {    B921600, B460800, B230400, B115200, B57600, B38400,    B19200,  B9600,   B4800,   B2400,   B1800,  B1200,    B600,    B300,    B150,    B110,    B75,    B50};static int speed_arr[] = {    921600,  460800,  230400,  115200,  57600,  38400,    19200,   9600,    4800,    2400,    1800,   1200,    600,     300,     150,     110,     75,     50};int speed_to_flag(int speed){    int i;     for (i = 0;  i < sizeof(speed_arr)/sizeof(int);  i++) {        if (speed == speed_arr[i]) {            return baudflag_arr[i];        }    }     fprintf(stderr, "Unsupported baudrate, use 9600 instead!\\n");    return B9600;}static struct termio oterm_attr;int setup_port(int fd, int baud, int databits, int parity, int stopbits){    struct termio term_attr;         if (ioctl(fd, TCGETA, &term_attr) < 0) {        return -1;    }         memcpy(&oterm_attr, &term_attr, sizeof(struct termio));     term_attr.c_iflag &= ~(INLCR | IGNCR | ICRNL | ISTRIP);    term_attr.c_oflag &= ~(OPOST | ONLCR | OCRNL);    term_attr.c_lflag &= ~(ISIG | ECHO | ICANON | NOFLSH);    term_attr.c_cflag &= ~CBAUD;    term_attr.c_cflag |= CREAD | speed_to_flag(baud);         term_attr.c_cflag &= ~(CSIZE);    switch (databits) {        case 5:            term_attr.c_cflag |= CS5;            break;         case 6:            term_attr.c_cflag |= CS6;            break;         case 7:            term_attr.c_cflag |= CS7;            break;         case 8:        default:            term_attr.c_cflag |= CS8;            break;    }         switch (parity) {        case 1:              term_attr.c_cflag |= (PARENB | PARODD);            break;         case 2:              term_attr.c_cflag |= PARENB;            term_attr.c_cflag &= ~(PARODD);            break;         case 0:          default:            term_attr.c_cflag &= ~(PARENB);            break;    }          switch (stopbits) {        case 2:              term_attr.c_cflag |= CSTOPB;            break;         case 1:          default:            term_attr.c_cflag &= ~CSTOPB;            break;    }     term_attr.c_cc[VMIN] = 1;    term_attr.c_cc[VTIME] = 0;     if (ioctl(fd, TCSETAW, &term_attr) < 0) {        return -1;    }     if (ioctl(fd, TCFLSH, 2) < 0) {        return -1;    }     return 0;}  int read_data(int fd, void *buf, int len){    int count;    int ret;     ret = 0;    count = 0;     //while (len > 0) {     ret = read(fd, (char*)buf + count, len);    if (ret < 1) {        fprintf(stderr, "Read error %s\\n", strerror(errno));        //break;    }     count += ret;    len = len - ret;     //}     *((char*)buf + count) = 0;    return count;}  int write_data(int fd, void *buf, int len){    int count;    int ret;     ret = 0;    count = 0;     while (len > 0) {         ret = write(fd, (char*)buf + count, len);        if (ret < 1) {            fprintf(stderr, "Write error %s\\n", strerror(errno));            break;        }         count += ret;        len = len - ret;    }     return count;}void print_usage(char *program_name){    fprintf(stderr,            "*************************************\\n"            "  A Simple Serial Port Test Utility\\n"            "*************************************\\n\\n"            "Usage:\\n  %s < device > < baud > < databits > < parity > < stopbits > \\n"            "       databits: 5, 6, 7, 8\\n"            "       parity: 0(None), 1(Odd), 2(Even)\\n"            "       stopbits: 1, 2\\n"            "Example:\\n  %s /dev/ttyS4 115200 8 0 1\\n\\n",            program_name, program_name           );}

運行效果如下：

審核編輯：湯梓紅

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