[SERIAL] Clean up and fix tty transmission start/stoping

The start_tx and stop_tx methods were passed a flag to indicate
whether the start/stop was from the tty start/stop callbacks, and
some drivers used this flag to decide whether to ask the UART to
immediately stop transmission (where the UART supports such a
feature.)

There are other cases when we wish this to occur - when CTS is
lowered, or if we change from soft to hard flow control and CTS
is inactive.  In these cases, this flag was false, and we would
allow the transmitter to drain before stopping.

There is really only one case where we want to let the transmitter
drain before disabling, and that's when we run out of characters
to send.

Hence, re-jig the start_tx and stop_tx methods to eliminate this
flag, and introduce new functions for the special "disable and
allow transmitter to drain" case.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

Documentation/serial/driver

@@ -111,24 +111,17 @@ hardware.
 	Interrupts: locally disabled.
 	This call must not sleep
 
-  stop_tx(port,tty_stop)
+  stop_tx(port)
 	Stop transmitting characters.  This might be due to the CTS
 	line becoming inactive or the tty layer indicating we want
-	to stop transmission.
-
-	tty_stop: 1 if this call is due to the TTY layer issuing a
-	          TTY stop to the driver (equiv to rs_stop).
+	to stop transmission due to an XOFF character.
 
 	Locking: port->lock taken.
 	Interrupts: locally disabled.
 	This call must not sleep
 
-  start_tx(port,tty_start)
-	start transmitting characters.  (incidentally, nonempty will
-	always be nonzero, and shouldn't be used - it will be dropped).
-
-	tty_start: 1 if this call was due to the TTY layer issuing
-	           a TTY start to the driver (equiv to rs_start)
+  start_tx(port)
+	start transmitting characters.
 
 	Locking: port->lock taken.
 	Interrupts: locally disabled.

drivers/serial/21285.c

@@ -58,17 +58,15 @@ static const char serial21285_name[] = "Footbridge UART";
  *  int((BAUD_BASE - (baud >> 1)) / baud)
  */
 
-static void
-serial21285_stop_tx(struct uart_port *port, unsigned int tty_stop)
+static void serial21285_stop_tx(struct uart_port *port)
 {
 	if (tx_enabled(port)) {
 		disable_irq(IRQ_CONTX);
 		tx_enabled(port) = 0;
 	}
 }
 
-static void
-serial21285_start_tx(struct uart_port *port, unsigned int tty_start)
+static void serial21285_start_tx(struct uart_port *port)
 {
 	if (!tx_enabled(port)) {
 		enable_irq(IRQ_CONTX);
@@ -148,7 +146,7 @@ static irqreturn_t serial21285_tx_chars(int irq, void *dev_id, struct pt_regs *r
 		goto out;
 	}
 	if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
-		serial21285_stop_tx(port, 0);
+		serial21285_stop_tx(port);
 		goto out;
 	}
 
@@ -164,7 +162,7 @@ static irqreturn_t serial21285_tx_chars(int irq, void *dev_id, struct pt_regs *r
 		uart_write_wakeup(port);
 
 	if (uart_circ_empty(xmit))
-		serial21285_stop_tx(port, 0);
+		serial21285_stop_tx(port);
 
  out:
 	return IRQ_HANDLED;

drivers/serial/8250.c

@@ -1001,7 +1001,7 @@ static inline void __stop_tx(struct uart_8250_port *p)
 	}
 }
 
-static void serial8250_stop_tx(struct uart_port *port, unsigned int tty_stop)
+static void serial8250_stop_tx(struct uart_port *port)
 {
 	struct uart_8250_port *up = (struct uart_8250_port *)port;
 
@@ -1018,7 +1018,7 @@ 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)
+static void serial8250_start_tx(struct uart_port *port)
 {
 	struct uart_8250_port *up = (struct uart_8250_port *)port;
 
@@ -1158,7 +1158,11 @@ static _INLINE_ void transmit_chars(struct uart_8250_port *up)
 		up->port.x_char = 0;
 		return;
 	}
-	if (uart_circ_empty(xmit) || uart_tx_stopped(&up->port)) {
+	if (uart_tx_stopped(&up->port)) {
+		serial8250_stop_tx(&up->port);
+		return;
+	}
+	if (uart_circ_empty(xmit)) {
 		__stop_tx(up);
 		return;
 	}

drivers/serial/amba-pl010.c

@@ -105,7 +105,7 @@ struct uart_amba_port {
 	unsigned int		old_status;
 };
 
-static void pl010_stop_tx(struct uart_port *port, unsigned int tty_stop)
+static void pl010_stop_tx(struct uart_port *port)
 {
 	unsigned int cr;
 
@@ -114,7 +114,7 @@ static void pl010_stop_tx(struct uart_port *port, unsigned int tty_stop)
 	UART_PUT_CR(port, cr);
 }
 
-static void pl010_start_tx(struct uart_port *port, unsigned int tty_start)
+static void pl010_start_tx(struct uart_port *port)
 {
 	unsigned int cr;
 
@@ -219,7 +219,7 @@ static void pl010_tx_chars(struct uart_port *port)
 		return;
 	}
 	if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
-		pl010_stop_tx(port, 0);
+		pl010_stop_tx(port);
 		return;
 	}
 
@@ -236,7 +236,7 @@ static void pl010_tx_chars(struct uart_port *port)
 		uart_write_wakeup(port);
 
 	if (uart_circ_empty(xmit))
-		pl010_stop_tx(port, 0);
+		pl010_stop_tx(port);
 }
 
 static void pl010_modem_status(struct uart_port *port)

drivers/serial/amba-pl011.c

@@ -74,15 +74,15 @@ struct uart_amba_port {
 	unsigned int		old_status;
 };
 
-static void pl011_stop_tx(struct uart_port *port, unsigned int tty_stop)
+static void pl011_stop_tx(struct uart_port *port)
 {
 	struct uart_amba_port *uap = (struct uart_amba_port *)port;
 
 	uap->im &= ~UART011_TXIM;
 	writew(uap->im, uap->port.membase + UART011_IMSC);
 }
 
-static void pl011_start_tx(struct uart_port *port, unsigned int tty_start)
+static void pl011_start_tx(struct uart_port *port)
 {
 	struct uart_amba_port *uap = (struct uart_amba_port *)port;
 
@@ -184,7 +184,7 @@ static void pl011_tx_chars(struct uart_amba_port *uap)
 		return;
 	}
 	if (uart_circ_empty(xmit) || uart_tx_stopped(&uap->port)) {
-		pl011_stop_tx(&uap->port, 0);
+		pl011_stop_tx(&uap->port);
 		return;
 	}
 
@@ -201,7 +201,7 @@ static void pl011_tx_chars(struct uart_amba_port *uap)
 		uart_write_wakeup(&uap->port);
 
 	if (uart_circ_empty(xmit))
-		pl011_stop_tx(&uap->port, 0);
+		pl011_stop_tx(&uap->port);
 }
 
 static void pl011_modem_status(struct uart_amba_port *uap)

drivers/serial/au1x00_uart.c

@@ -200,7 +200,7 @@ static void autoconfig(struct uart_8250_port *up, unsigned int probeflags)
 	DEBUG_AUTOCONF("type=%s\n", uart_config[up->port.type].name);
 }
 
-static void serial8250_stop_tx(struct uart_port *port, unsigned int tty_stop)
+static void serial8250_stop_tx(struct uart_port *port)
 {
 	struct uart_8250_port *up = (struct uart_8250_port *)port;
 
@@ -210,7 +210,7 @@ static void serial8250_stop_tx(struct uart_port *port, unsigned int tty_stop)
 	}
 }
 
-static void serial8250_start_tx(struct uart_port *port, unsigned int tty_start)
+static void serial8250_start_tx(struct uart_port *port)
 {
 	struct uart_8250_port *up = (struct uart_8250_port *)port;
 
@@ -337,7 +337,7 @@ static _INLINE_ void transmit_chars(struct uart_8250_port *up)
 		return;
 	}
 	if (uart_circ_empty(xmit) || uart_tx_stopped(&up->port)) {
-		serial8250_stop_tx(&up->port, 0);
+		serial8250_stop_tx(&up->port);
 		return;
 	}
 
@@ -356,7 +356,7 @@ static _INLINE_ void transmit_chars(struct uart_8250_port *up)
 	DEBUG_INTR("THRE...");
 
 	if (uart_circ_empty(xmit))
-		serial8250_stop_tx(&up->port, 0);
+		serial8250_stop_tx(&up->port);
 }
 
 static _INLINE_ void check_modem_status(struct uart_8250_port *up)

drivers/serial/clps711x.c

@@ -69,17 +69,15 @@
 
 #define tx_enabled(port)	((port)->unused[0])
 
-static void
-clps711xuart_stop_tx(struct uart_port *port, unsigned int tty_stop)
+static void clps711xuart_stop_tx(struct uart_port *port)
 {
 	if (tx_enabled(port)) {
 		disable_irq(TX_IRQ(port));
 		tx_enabled(port) = 0;
 	}
 }
 
-static void
-clps711xuart_start_tx(struct uart_port *port, unsigned int tty_start)
+static void clps711xuart_start_tx(struct uart_port *port)
 {
 	if (!tx_enabled(port)) {
 		enable_irq(TX_IRQ(port));
@@ -165,7 +163,7 @@ static irqreturn_t clps711xuart_int_tx(int irq, void *dev_id, struct pt_regs *re
 		return IRQ_HANDLED;
 	}
 	if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
-		clps711xuart_stop_tx(port, 0);
+		clps711xuart_stop_tx(port);
 		return IRQ_HANDLED;
 	}
 
@@ -182,7 +180,7 @@ static irqreturn_t clps711xuart_int_tx(int irq, void *dev_id, struct pt_regs *re
 		uart_write_wakeup(port);
 
 	if (uart_circ_empty(xmit))
-		clps711xuart_stop_tx(port, 0);
+		clps711xuart_stop_tx(port);
 
 	return IRQ_HANDLED;
 }

drivers/serial/cpm_uart/cpm_uart_core.c

@@ -124,7 +124,7 @@ static unsigned int cpm_uart_get_mctrl(struct uart_port *port)
 /*
  * Stop transmitter
  */
-static void cpm_uart_stop_tx(struct uart_port *port, unsigned int tty_stop)
+static void cpm_uart_stop_tx(struct uart_port *port)
 {
 	struct uart_cpm_port *pinfo = (struct uart_cpm_port *)port;
 	volatile smc_t *smcp = pinfo->smcp;
@@ -141,7 +141,7 @@ static void cpm_uart_stop_tx(struct uart_port *port, unsigned int tty_stop)
 /*
  * Start transmitter
  */
-static void cpm_uart_start_tx(struct uart_port *port, unsigned int tty_start)
+static void cpm_uart_start_tx(struct uart_port *port)
 {
 	struct uart_cpm_port *pinfo = (struct uart_cpm_port *)port;
 	volatile smc_t *smcp = pinfo->smcp;
@@ -623,7 +623,7 @@ static int cpm_uart_tx_pump(struct uart_port *port)
 	}
 
 	if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
-		cpm_uart_stop_tx(port, 0);
+		cpm_uart_stop_tx(port);
 		return 0;
 	}
 
@@ -656,7 +656,7 @@ static int cpm_uart_tx_pump(struct uart_port *port)
 		uart_write_wakeup(port);
 
 	if (uart_circ_empty(xmit)) {
-		cpm_uart_stop_tx(port, 0);
+		cpm_uart_stop_tx(port);
 		return 0;
 	}
 

drivers/serial/dz.c

@@ -112,7 +112,7 @@ static inline void dz_out(struct dz_port *dport, unsigned offset,
  * ------------------------------------------------------------
  */
 
-static void dz_stop_tx(struct uart_port *uport, unsigned int tty_stop)
+static void dz_stop_tx(struct uart_port *uport)
 {
 	struct dz_port *dport = (struct dz_port *)uport;
 	unsigned short tmp, mask = 1 << dport->port.line;
@@ -125,7 +125,7 @@ static void dz_stop_tx(struct uart_port *uport, unsigned int tty_stop)
 	spin_unlock_irqrestore(&dport->port.lock, flags);
 }
 
-static void dz_start_tx(struct uart_port *uport, unsigned int tty_start)
+static void dz_start_tx(struct uart_port *uport)
 {
 	struct dz_port *dport = (struct dz_port *)uport;
 	unsigned short tmp, mask = 1 << dport->port.line;
@@ -290,7 +290,7 @@ static inline void dz_transmit_chars(struct dz_port *dport)
 	}
 	/* if nothing to do or stopped or hardware stopped */
 	if (uart_circ_empty(xmit) || uart_tx_stopped(&dport->port)) {
-		dz_stop_tx(&dport->port, 0);
+		dz_stop_tx(&dport->port);
 		return;
 	}
 
@@ -308,7 +308,7 @@ static inline void dz_transmit_chars(struct dz_port *dport)
 
 	/* Are we done */
 	if (uart_circ_empty(xmit))
-		dz_stop_tx(&dport->port, 0);
+		dz_stop_tx(&dport->port);
 }
 
 /*
@@ -440,7 +440,7 @@ static int dz_startup(struct uart_port *uport)
  */
 static void dz_shutdown(struct uart_port *uport)
 {
-	dz_stop_tx(uport, 0);
+	dz_stop_tx(uport);
 }
 
 /*

drivers/serial/icom.c

@@ -989,18 +989,16 @@ static unsigned int icom_get_mctrl(struct uart_port *port)
 	return result;
 }
 
-static void icom_stop_tx(struct uart_port *port, unsigned int tty_stop)
+static void icom_stop_tx(struct uart_port *port)
 {
 	unsigned char cmdReg;
 
-	if (tty_stop) {
-		trace(ICOM_PORT, "STOP", 0);
-		cmdReg = readb(&ICOM_PORT->dram->CmdReg);
-		writeb(cmdReg | CMD_HOLD_XMIT, &ICOM_PORT->dram->CmdReg);
-	}
+	trace(ICOM_PORT, "STOP", 0);
+	cmdReg = readb(&ICOM_PORT->dram->CmdReg);
+	writeb(cmdReg | CMD_HOLD_XMIT, &ICOM_PORT->dram->CmdReg);
 }
 
-static void icom_start_tx(struct uart_port *port, unsigned int tty_start)
+static void icom_start_tx(struct uart_port *port)
 {
 	unsigned char cmdReg;
 

drivers/serial/imx.c

@@ -124,7 +124,7 @@ static void imx_timeout(unsigned long data)
 /*
  * interrupts disabled on entry
  */
-static void imx_stop_tx(struct uart_port *port, unsigned int tty_stop)
+static void imx_stop_tx(struct uart_port *port)
 {
 	struct imx_port *sport = (struct imx_port *)port;
 	UCR1((u32)sport->port.membase) &= ~UCR1_TXMPTYEN;
@@ -165,13 +165,13 @@ static inline void imx_transmit_buffer(struct imx_port *sport)
 	} while (!(UTS((u32)sport->port.membase) & UTS_TXFULL));
 
 	if (uart_circ_empty(xmit))
-		imx_stop_tx(&sport->port, 0);
+		imx_stop_tx(&sport->port);
 }
 
 /*
  * interrupts disabled on entry
  */
-static void imx_start_tx(struct uart_port *port, unsigned int tty_start)
+static void imx_start_tx(struct uart_port *port)
 {
 	struct imx_port *sport = (struct imx_port *)port;
 
@@ -196,7 +196,7 @@ static irqreturn_t imx_txint(int irq, void *dev_id, struct pt_regs *regs)
 	}
 
 	if (uart_circ_empty(xmit) || uart_tx_stopped(&sport->port)) {
-		imx_stop_tx(&sport->port, 0);
+		imx_stop_tx(&sport->port);
 		goto out;
 	}