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Commit 5e42e9a3 authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
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serial: imx: Fix x_char handling and tx flow control 



The serial core expects the UART driver to transmit x_char
(START/STOP chars) even if tx is stopped and before data already
in the tx ring buffer if possible. Also, sending x_char must
not cause additional data in the tx ring buffer to transmit
if tx is stopped.

Cause x_char to be transmitted before any other data is sent.
Auto-stop tx if the tx ring buffer is empty or tx should be stopped.
Only perform one write wakeup if tx ring buffer space is below
threshold.

x_char handling in DMA mode is still broken; add FIXME.

Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 99abf3b9

drivers/tty/serial/imx.c

+16 −23
Original line number Diff line number Diff line
@@ -464,9 +464,19 @@ static inline void imx_transmit_buffer(struct imx_port *sport) 
{

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



	if (sport->port.x_char) {

		/* Send next char */

		writel(sport->port.x_char, sport->port.membase + URTX0);

		return;

	}



	if (uart_circ_empty(xmit) || uart_tx_stopped(&sport->port)) {

		imx_stop_tx(&sport->port);

		return;

	}



	while (!uart_circ_empty(xmit) &&

			!(readl(sport->port.membase + uts_reg(sport))

				& UTS_TXFULL)) {

	       !(readl(sport->port.membase + uts_reg(sport)) & UTS_TXFULL)) {

		/* send xmit->buf[xmit->tail]

		 * out the port here */

		writel(xmit->buf[xmit->tail], sport->port.membase + URTX0);
@@ -567,9 +577,6 @@ static void imx_start_tx(struct uart_port *port) 
	struct imx_port *sport = (struct imx_port *)port;

	unsigned long temp;



	if (uart_circ_empty(&port->state->xmit))

		return;



	if (USE_IRDA(sport)) {

		/* half duplex in IrDA mode; have to disable receive mode */

		temp = readl(sport->port.membase + UCR4);
@@ -604,6 +611,9 @@ static void imx_start_tx(struct uart_port *port) 
	}



	if (sport->dma_is_enabled) {

		/* FIXME: port->x_char must be transmitted if != 0 */

		if (!uart_circ_empty(&port->state->xmit) &&

		    !uart_tx_stopped(port))

			imx_dma_tx(sport);

		return;

	}
@@ -632,27 +642,10 @@ static irqreturn_t imx_rtsint(int irq, void *dev_id) 
static irqreturn_t imx_txint(int irq, void *dev_id)

{

	struct imx_port *sport = dev_id;

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

	unsigned long flags;



	spin_lock_irqsave(&sport->port.lock, flags);

	if (sport->port.x_char) {

		/* Send next char */

		writel(sport->port.x_char, sport->port.membase + URTX0);

		goto out;

	}



	if (uart_circ_empty(xmit) || uart_tx_stopped(&sport->port)) {

		imx_stop_tx(&sport->port);

		goto out;

	}



	imx_transmit_buffer(sport);



	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)

		uart_write_wakeup(&sport->port);



out:

	spin_unlock_irqrestore(&sport->port.lock, flags);

	return IRQ_HANDLED;

}