Linux4.1 for IMX6UL ，RS232 driver does not use CTS, use an additional GPIO control to receive and send, which changed the RS485 driver?

jsj2000lyz — Sat, 10 Dec 2016 14:50:40 GMT

I found a function which named - static void imx_start_tx (struct uart_port * port) in the source code of the linux nernel 4.1 for IMX6UL, here how to changed the RS232 driver code to control the GPIO port used to control RS485 send and receive?

Thanks!

The code file name and directory：Imx.c (linux-src\drivers\tty\serial)

The function code：

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;
}
}

Thanks again !

Re: Linux4.1 for IMX6UL ，RS232 driver does not use CTS, use an additional GPIO control to receive and send, which changed the RS485 driver?

igorpadykov — Sun, 11 Dec 2016 23:27:46 GMT

if you are trying replace CTS flow control signal with gpio one can try below changes:

temp &= ~UCR2_CTS; <----- replace with gpio assert
else
temp |= UCR2_CTS;
writel(temp, port->membase + UCR2); <----- replace with gpio deassert

Best regards
igor
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topic Re: Linux4.1 for IMX6UL ，RS232 driver does not use CTS, use an additional GPIO control to receive and send, which changed the RS485 driver? in i.MX Processors

Linux4.1 for IMX6UL ，RS232 driver does not use CTS, use an additional GPIO control to receive and send, which changed the RS485 driver?

Re: Linux4.1 for IMX6UL ，RS232 driver does not use CTS, use an additional GPIO control to receive and send, which changed the RS485 driver?