【MA35D1】如何修改驱动，支持GPIO控制RS-485方向

RS-485.zip

1、在DTS文件中增加rts-gpio及其管脚配置

&uart12 {

status = "okay";

pinctrl-names = "default";

pinctrl-0 = <&pinctrl_uart12>;

rts-gpio = <&gpioi 1 0>;

};

&uart14 {

status = "okay";

pinctrl-names = "default";

pinctrl-0 = <&pinctrl_uart14>;

rts-gpio = <&gpioi 5 0>;

};

2、在驱动文件ma35d1_serial.c中结构体uart_ma35d1_port增加变量int rts_gpio;

3、在probe函数里面增加获取rts_gpio的代码：

up->rts_gpio = of_get_named_gpio(pdev->dev.of_node, "rts-gpio", 0);

if (gpio_is_valid(up->rts_gpio)) {

pr_err("test will request gpio\n");

                ret = devm_gpio_request(up->port.dev,

                                        up->rts_gpio, "RTS");

                if (ret) {

                        dev_err(&pdev->dev,

                                "error requesting RTS GPIO\n");

                }

                ret = gpio_direction_output(up->rts_gpio,0);

                if (ret) {

                        dev_err(&pdev->dev, "error setting RTS GPIO\n");

                }

        }else{

pr_err("test port do not have rts_port\n");

up->rts_gpio=-EINVAL;

}

4、增加修改极性的函数

static void set_rs485_rst(struct uart_ma35d1_port *p,int value)

{

int i=0;

i= value;

if(p->rts_gpio != -EINVAL){

        gpio_direction_output(p->rts_gpio,i);

}

}

5、在合适的地方调用步骤4增加的函数

static inline void __stop_tx(struct uart_ma35d1_port *p)

{

unsigned int ier;

ier = serial_in(p, UART_REG_IER);

if (ier & THRE_IEN){

if(p->rts_gpio!=-EINVAL){

if(serial_in(p,UART_REG_FSR)&TE_FLAG){

set_rs485_rst(p,0);

serial_out(p, UART_REG_IER, ier & ~THRE_IEN);

}

}else{

serial_out(p, UART_REG_IER, ier & ~THRE_IEN);

}

}

if (p->rs485.flags & SER_RS485_ENABLED)

rs485_start_rx(p);

}

static void ma35d1serial_start_tx(struct uart_port *port)

{

struct uart_ma35d1_port *up = (struct uart_ma35d1_port *)port;

unsigned int ier;

struct circ_buf *xmit = &up->port.state->xmit;

set_rs485_rst(up,1);

if (up->rs485.flags & SER_RS485_ENABLED)

rs485_stop_rx(up);

......