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Commit 55d3b282 authored by Russell King's avatar Russell King
Browse files

[PATCH] Serial: Mobility's 16550A ports need a helping hand 



The Mobility 16550A serial ports don't behave the same as standard
16550A ports, and need a helping hand to get them going once the
transmitter has drained and been disabled.

Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 4ba5e35d

drivers/serial/8250.c

+31 −0
Original line number Diff line number Diff line
@@ -1027,6 +1027,8 @@ static void serial8250_stop_tx(struct uart_port *port, unsigned int tty_stop) 
	}

}



static void transmit_chars(struct uart_8250_port *up);



static void serial8250_start_tx(struct uart_port *port, unsigned int tty_start)

{

	struct uart_8250_port *up = (struct uart_8250_port *)port;
@@ -1034,6 +1036,14 @@ static void serial8250_start_tx(struct uart_port *port, unsigned int tty_start) 
	if (!(up->ier & UART_IER_THRI)) {

		up->ier |= UART_IER_THRI;

		serial_out(up, UART_IER, up->ier);



		if (up->capabilities & UART_BUG_TXEN) {

			unsigned char lsr, iir;

			lsr = serial_in(up, UART_LSR);

			iir = serial_in(up, UART_IIR);

			if (lsr & UART_LSR_TEMT && iir & UART_IIR_NO_INT)

				transmit_chars(up);

		}

	}

	/*

	 * We only do this from uart_start
@@ -1439,6 +1449,7 @@ static int serial8250_startup(struct uart_port *port) 
{

	struct uart_8250_port *up = (struct uart_8250_port *)port;

	unsigned long flags;

	unsigned char lsr, iir;

	int retval;



	up->capabilities = uart_config[up->port.type].flags;
@@ -1542,6 +1553,26 @@ static int serial8250_startup(struct uart_port *port) 
			up->port.mctrl |= TIOCM_OUT2;



	serial8250_set_mctrl(&up->port, up->port.mctrl);



	/*

	 * Do a quick test to see if we receive an

	 * interrupt when we enable the TX irq.

	 */

	serial_outp(up, UART_IER, UART_IER_THRI);

	lsr = serial_in(up, UART_LSR);

	iir = serial_in(up, UART_IIR);

	serial_outp(up, UART_IER, 0);



	if (lsr & UART_LSR_TEMT && iir & UART_IIR_NO_INT) {

		if (!(up->capabilities & UART_BUG_TXEN)) {

			up->capabilities |= UART_BUG_TXEN;

			pr_debug("ttyS%d - enabling bad tx status workarounds\n",

				 port->line);

		}

	} else {

		up->capabilities &= ~UART_BUG_TXEN;

	}



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



	/*

drivers/serial/8250.h

+1 −0
Original line number Diff line number Diff line
@@ -52,6 +52,7 @@ struct serial8250_config { 
#define UART_CAP_UUE	(1 << 12)	/* UART needs IER bit 6 set (Xscale) */



#define UART_BUG_QUOT	(1 << 0)	/* UART has buggy quot LSB */

#define UART_BUG_TXEN	(1 << 1)	/* UART has buggy TX IIR status */



#if defined(__i386__) && (defined(CONFIG_M386) || defined(CONFIG_M486))

#define _INLINE_ inline