imx6ul A7核心 linux系统，RS232驱动中增加GPIO控制改成RS485驱动的问题？

[lyz007]

原版RS232驱动源码中的imx_start_tx函数原型如下：
static void imx_start_tx(struct uart_port *port)
static void imx_start_tx(struct uart_port *port)
{
struct imx_port *sport = (struct imx_port *)port;
unsigned long temp;

if (port->rs485.flags & SER_RS485_ENABLED) {
/* enable transmitter and shifter empty irq */
temp = readl(port->membase + UCR2);
if (port->rs485.flags & SER_RS485_RTS_ON_SEND)
temp &= ~UCR2_CTS;
else
temp |= UCR2_CTS;
writel(temp, port->membase + UCR2);

temp = readl(port->membase + UCR4);
temp |= UCR4_TCEN;
writel(temp, port->membase + UCR4);
}

if (!sport->dma_is_enabled) {
temp = readl(sport->port.membase + UCR1);
writel(temp | UCR1_TXMPTYEN, sport->port.membase + UCR1);
}

if (sport->dma_is_enabled) {
if (sport->port.x_char) {
/* We have X-char to send, so enable TX IRQ and
* disable TX DMA to let TX interrupt to send X-char */
temp = readl(sport->port.membase + UCR1);
temp &= ~UCR1_TDMAEN;
temp |= UCR1_TXMPTYEN;
writel(temp, sport->port.membase + UCR1);
return;
}

schedule_delayed_work(&sport->tsk_dma_tx, 0);
return;
}
}
硬件和系统分别是imx6ul A7核心和linux系统
想要在这里增加对GPIO端口的控制应该怎么处理？请高手帮忙？？？？