Merge branch 'omap-serial' of git://git.linaro.org/people/rmk/linux-arm

Pull ARM OMAP serial updates from Russell King:
 "This series is a major reworking of the OMAP serial driver code fixing
  various bugs in the hardware-assisted flow control, extending up into
  serial_core for a couple of issues.  These fixes have been done as a
  set of progressive changes and transformations in the hope that no new
  bugs will be introduced by this series.

  The problems are many-fold, from the driver not being informed about
  updated settings, to the driver not knowing what the intentions of the
  upper layers are.

  The first four patches tackle the serial_core layer, allowing it to
  provide the necessary information to drivers, and the remaining
  patches allow the OMAP serial driver to take advantage of this.

  This brings hardware assisted RTS/CTS and XON/OFF flow control into a
  useful state.

  These patches have been in linux-next for most of the last cycle;
  indeed they predate the previous merge window.  They've also been
  posted to the OMAP people."

* 'omap-serial' of git://git.linaro.org/people/rmk/linux-arm: (21 commits)
  SERIAL: omap: fix hardware assisted flow control
  SERIAL: omap: simplify (2)
  SERIAL: omap: move xon/xoff setting earlier
  SERIAL: omap: always set TCR
  SERIAL: omap: simplify
  SERIAL: omap: don't read back LCR/MCR/EFR
  SERIAL: omap: serial_omap_configure_xonxoff() contents into set_termios
  SERIAL: omap: configure xon/xoff before setting modem control lines
  SERIAL: omap: remove OMAP_UART_SYSC_RESET and OMAP_UART_FIFO_CLR
  SERIAL: omap: move driver private definitions and structures to driver
  SERIAL: omap: remove 'irq_pending' bitfield
  SERIAL: omap: fix MCR TCRTLR bit handling
  SERIAL: omap: fix set_mctrl() breakage
  SERIAL: omap: no need to re-read EFR
  SERIAL: omap: remove setting of EFR SCD bit
  SERIAL: omap: allow hardware assisted IXANY mode to be disabled
  SERIAL: omap: allow hardware assisted rts/cts modes to be disabled
  SERIAL: core: add throttle/unthrottle callbacks for hardware assisted flow control
  SERIAL: core: add hardware assisted h/w flow control support
  SERIAL: core: add hardware assisted s/w flow control support
  ...

Conflicts:
	drivers/tty/serial/omap-serial.c

arch/arm/plat-omap/include/plat/omap-serial.h

@@ -30,35 +30,6 @@
  */
 #define OMAP_SERIAL_NAME	"ttyO"
 
-#define OMAP_MODE13X_SPEED	230400
-
-#define OMAP_UART_SCR_TX_EMPTY	0x08
-
-/* WER = 0x7F
- * Enable module level wakeup in WER reg
- */
-#define OMAP_UART_WER_MOD_WKUP	0X7F
-
-/* Enable XON/XOFF flow control on output */
-#define OMAP_UART_SW_TX		0x04
-
-/* Enable XON/XOFF flow control on input */
-#define OMAP_UART_SW_RX		0x04
-
-#define OMAP_UART_SYSC_RESET	0X07
-#define OMAP_UART_TCR_TRIG	0X0F
-#define OMAP_UART_SW_CLR	0XF0
-#define OMAP_UART_FIFO_CLR	0X06
-
-#define OMAP_UART_DMA_CH_FREE	-1
-
-#define OMAP_MAX_HSUART_PORTS	6
-
-#define MSR_SAVE_FLAGS		UART_MSR_ANY_DELTA
-
-#define UART_ERRATA_i202_MDR1_ACCESS	BIT(0)
-#define UART_ERRATA_i291_DMA_FORCEIDLE	BIT(1)
-
 struct omap_uart_port_info {
 	bool			dma_enabled;	/* To specify DMA Mode */
 	unsigned int		uartclk;	/* UART clock rate */
@@ -77,30 +48,4 @@ struct omap_uart_port_info {
 	void (*enable_wakeup)(struct device *, bool);
 };
 
-struct uart_omap_dma {
-	u8			uart_dma_tx;
-	u8			uart_dma_rx;
-	int			rx_dma_channel;
-	int			tx_dma_channel;
-	dma_addr_t		rx_buf_dma_phys;
-	dma_addr_t		tx_buf_dma_phys;
-	unsigned int		uart_base;
-	/*
-	 * Buffer for rx dma.It is not required for tx because the buffer
-	 * comes from port structure.
-	 */
-	unsigned char		*rx_buf;
-	unsigned int		prev_rx_dma_pos;
-	int			tx_buf_size;
-	int			tx_dma_used;
-	int			rx_dma_used;
-	spinlock_t		tx_lock;
-	spinlock_t		rx_lock;
-	/* timer to poll activity on rx dma */
-	struct timer_list	rx_timer;
-	unsigned int		rx_buf_size;
-	unsigned int		rx_poll_rate;
-	unsigned int		rx_timeout;
-};
-
 #endif /* __OMAP_SERIAL_H__ */

drivers/tty/serial/omap-serial.c

@@ -44,6 +44,8 @@
 
 #include <plat/omap-serial.h>
 
+#define OMAP_MAX_HSUART_PORTS	6
+
 #define UART_BUILD_REVISION(x, y)	(((x) << 8) | (y))
 
 #define OMAP_UART_REV_42 0x0402
@@ -51,10 +53,14 @@
 #define OMAP_UART_REV_52 0x0502
 #define OMAP_UART_REV_63 0x0603
 
+#define UART_ERRATA_i202_MDR1_ACCESS	BIT(0)
+#define UART_ERRATA_i291_DMA_FORCEIDLE	BIT(1)
+
 #define DEFAULT_CLK_SPEED 48000000 /* 48Mhz*/
 
 /* SCR register bitmasks */
 #define OMAP_UART_SCR_RX_TRIG_GRANU1_MASK		(1 << 7)
+#define OMAP_UART_SCR_TX_EMPTY			(1 << 3)
 
 /* FCR register bitmasks */
 #define OMAP_UART_FCR_RX_FIFO_TRIG_MASK			(0x3 << 6)
@@ -71,6 +77,52 @@
 #define OMAP_UART_MVR_MAJ_SHIFT		8
 #define OMAP_UART_MVR_MIN_MASK		0x3f
 
+#define OMAP_UART_DMA_CH_FREE	-1
+
+#define MSR_SAVE_FLAGS		UART_MSR_ANY_DELTA
+#define OMAP_MODE13X_SPEED	230400
+
+/* WER = 0x7F
+ * Enable module level wakeup in WER reg
+ */
+#define OMAP_UART_WER_MOD_WKUP	0X7F
+
+/* Enable XON/XOFF flow control on output */
+#define OMAP_UART_SW_TX		0x08
+
+/* Enable XON/XOFF flow control on input */
+#define OMAP_UART_SW_RX		0x02
+
+#define OMAP_UART_SW_CLR	0xF0
+
+#define OMAP_UART_TCR_TRIG	0x0F
+
+struct uart_omap_dma {
+	u8			uart_dma_tx;
+	u8			uart_dma_rx;
+	int			rx_dma_channel;
+	int			tx_dma_channel;
+	dma_addr_t		rx_buf_dma_phys;
+	dma_addr_t		tx_buf_dma_phys;
+	unsigned int		uart_base;
+	/*
+	 * Buffer for rx dma.It is not required for tx because the buffer
+	 * comes from port structure.
+	 */
+	unsigned char		*rx_buf;
+	unsigned int		prev_rx_dma_pos;
+	int			tx_buf_size;
+	int			tx_dma_used;
+	int			rx_dma_used;
+	spinlock_t		tx_lock;
+	spinlock_t		rx_lock;
+	/* timer to poll activity on rx dma */
+	struct timer_list	rx_timer;
+	unsigned int		rx_buf_size;
+	unsigned int		rx_poll_rate;
+	unsigned int		rx_timeout;
+};
+
 struct uart_omap_port {
 	struct uart_port	port;
 	struct uart_omap_dma	uart_dma;
@@ -99,7 +151,6 @@ struct uart_omap_port {
 	int			context_loss_cnt;
 	u32			errata;
 	u8			wakeups_enabled;
-	unsigned int		irq_pending:1;
 
 	int			DTR_gpio;
 	int			DTR_inverted;
@@ -303,6 +354,34 @@ static void serial_omap_start_tx(struct uart_port *port)
 	pm_runtime_put_autosuspend(up->dev);
 }
 
+static void serial_omap_throttle(struct uart_port *port)
+{
+	struct uart_omap_port *up = to_uart_omap_port(port);
+	unsigned long flags;
+
+	pm_runtime_get_sync(up->dev);
+	spin_lock_irqsave(&up->port.lock, flags);
+	up->ier &= ~(UART_IER_RLSI | UART_IER_RDI);
+	serial_out(up, UART_IER, up->ier);
+	spin_unlock_irqrestore(&up->port.lock, flags);
+	pm_runtime_mark_last_busy(up->dev);
+	pm_runtime_put_autosuspend(up->dev);
+}
+
+static void serial_omap_unthrottle(struct uart_port *port)
+{
+	struct uart_omap_port *up = to_uart_omap_port(port);
+	unsigned long flags;
+
+	pm_runtime_get_sync(up->dev);
+	spin_lock_irqsave(&up->port.lock, flags);
+	up->ier |= UART_IER_RLSI | UART_IER_RDI;
+	serial_out(up, UART_IER, up->ier);
+	spin_unlock_irqrestore(&up->port.lock, flags);
+	pm_runtime_mark_last_busy(up->dev);
+	pm_runtime_put_autosuspend(up->dev);
+}
+
 static unsigned int check_modem_status(struct uart_omap_port *up)
 {
 	unsigned int status;
@@ -504,7 +583,7 @@ static unsigned int serial_omap_get_mctrl(struct uart_port *port)
 static void serial_omap_set_mctrl(struct uart_port *port, unsigned int mctrl)
 {
 	struct uart_omap_port *up = to_uart_omap_port(port);
-	unsigned char mcr = 0;
+	unsigned char mcr = 0, old_mcr;
 
 	dev_dbg(up->port.dev, "serial_omap_set_mctrl+%d\n", up->port.line);
 	if (mctrl & TIOCM_RTS)
@@ -519,8 +598,10 @@ static void serial_omap_set_mctrl(struct uart_port *port, unsigned int mctrl)
 		mcr |= UART_MCR_LOOP;
 
 	pm_runtime_get_sync(up->dev);
-	up->mcr = serial_in(up, UART_MCR);
-	up->mcr |= mcr;
+	old_mcr = serial_in(up, UART_MCR);
+	old_mcr &= ~(UART_MCR_LOOP | UART_MCR_OUT2 | UART_MCR_OUT1 |
+		     UART_MCR_DTR | UART_MCR_RTS);
+	up->mcr = old_mcr | mcr;
 	serial_out(up, UART_MCR, up->mcr);
 	pm_runtime_mark_last_busy(up->dev);
 	pm_runtime_put_autosuspend(up->dev);
@@ -654,61 +735,6 @@ static void serial_omap_shutdown(struct uart_port *port)
 	free_irq(up->port.irq, up);
 }
 
-static inline void
-serial_omap_configure_xonxoff
-		(struct uart_omap_port *up, struct ktermios *termios)
-{
-	up->lcr = serial_in(up, UART_LCR);
-	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
-	up->efr = serial_in(up, UART_EFR);
-	serial_out(up, UART_EFR, up->efr & ~UART_EFR_ECB);
-
-	serial_out(up, UART_XON1, termios->c_cc[VSTART]);
-	serial_out(up, UART_XOFF1, termios->c_cc[VSTOP]);
-
-	/* clear SW control mode bits */
-	up->efr &= OMAP_UART_SW_CLR;
-
-	/*
-	 * IXON Flag:
-	 * Enable XON/XOFF flow control on output.
-	 * Transmit XON1, XOFF1
-	 */
-	if (termios->c_iflag & IXON)
-		up->efr |= OMAP_UART_SW_TX;
-
-	/*
-	 * IXOFF Flag:
-	 * Enable XON/XOFF flow control on input.
-	 * Receiver compares XON1, XOFF1.
-	 */
-	if (termios->c_iflag & IXOFF)
-		up->efr |= OMAP_UART_SW_RX;
-
-	serial_out(up, UART_EFR, up->efr | UART_EFR_ECB);
-	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_A);
-
-	up->mcr = serial_in(up, UART_MCR);
-
-	/*
-	 * IXANY Flag:
-	 * Enable any character to restart output.
-	 * Operation resumes after receiving any
-	 * character after recognition of the XOFF character
-	 */
-	if (termios->c_iflag & IXANY)
-		up->mcr |= UART_MCR_XONANY;
-
-	serial_out(up, UART_MCR, up->mcr | UART_MCR_TCRTLR);
-	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
-	serial_out(up, UART_TI752_TCR, OMAP_UART_TCR_TRIG);
-
-	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_A);
-
-	serial_out(up, UART_MCR, up->mcr & ~UART_MCR_TCRTLR);
-	serial_out(up, UART_LCR, up->lcr);
-}
-
 static void serial_omap_uart_qos_work(struct work_struct *work)
 {
 	struct uart_omap_port *up = container_of(work, struct uart_omap_port,
@@ -726,7 +752,6 @@ serial_omap_set_termios(struct uart_port *port, struct ktermios *termios,
 {
 	struct uart_omap_port *up = to_uart_omap_port(port);
 	unsigned char cval = 0;
-	unsigned char efr = 0;
 	unsigned long flags = 0;
 	unsigned int baud, quot;
 
@@ -836,11 +861,12 @@ serial_omap_set_termios(struct uart_port *port, struct ktermios *termios,
 
 	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
 
-	up->efr = serial_in(up, UART_EFR);
+	up->efr = serial_in(up, UART_EFR) & ~UART_EFR_ECB;
+	up->efr &= ~UART_EFR_SCD;
 	serial_out(up, UART_EFR, up->efr | UART_EFR_ECB);
 
 	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_A);
-	up->mcr = serial_in(up, UART_MCR);
+	up->mcr = serial_in(up, UART_MCR) & ~UART_MCR_TCRTLR;
 	serial_out(up, UART_MCR, up->mcr | UART_MCR_TCRTLR);
 	/* FIFO ENABLE, DMA MODE */
 
@@ -859,9 +885,12 @@ serial_omap_set_termios(struct uart_port *port, struct ktermios *termios,
 
 	serial_out(up, UART_OMAP_SCR, up->scr);
 
-	serial_out(up, UART_EFR, up->efr);
+	/* Reset UART_MCR_TCRTLR: this must be done with the EFR_ECB bit set */
 	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_A);
 	serial_out(up, UART_MCR, up->mcr);
+	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
+	serial_out(up, UART_EFR, up->efr);
+	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_A);
 
 	/* Protocol, Baud Rate, and Interrupt Settings */
 
@@ -871,8 +900,6 @@ serial_omap_set_termios(struct uart_port *port, struct ktermios *termios,
 		serial_out(up, UART_OMAP_MDR1, up->mdr1);
 
 	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
-
-	up->efr = serial_in(up, UART_EFR);
 	serial_out(up, UART_EFR, up->efr | UART_EFR_ECB);
 
 	serial_out(up, UART_LCR, 0);
@@ -899,29 +926,68 @@ serial_omap_set_termios(struct uart_port *port, struct ktermios *termios,
 	else
 		serial_out(up, UART_OMAP_MDR1, up->mdr1);
 
-	/* Hardware Flow Control Configuration */
-
-	if (termios->c_cflag & CRTSCTS) {
-		efr |= (UART_EFR_CTS | UART_EFR_RTS);
-		serial_out(up, UART_LCR, UART_LCR_CONF_MODE_A);
+	/* Configure flow control */
+	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
 
-		up->mcr = serial_in(up, UART_MCR);
-		serial_out(up, UART_MCR, up->mcr | UART_MCR_TCRTLR);
+	/* XON1/XOFF1 accessible mode B, TCRTLR=0, ECB=0 */
+	serial_out(up, UART_XON1, termios->c_cc[VSTART]);
+	serial_out(up, UART_XOFF1, termios->c_cc[VSTOP]);
 
-		serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
-		up->efr = serial_in(up, UART_EFR);
+	/* Enable access to TCR/TLR */
 	serial_out(up, UART_EFR, up->efr | UART_EFR_ECB);
+	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_A);
+	serial_out(up, UART_MCR, up->mcr | UART_MCR_TCRTLR);
 
 	serial_out(up, UART_TI752_TCR, OMAP_UART_TCR_TRIG);
-		serial_out(up, UART_EFR, efr); /* Enable AUTORTS and AUTOCTS */
-		serial_out(up, UART_LCR, UART_LCR_CONF_MODE_A);
-		serial_out(up, UART_MCR, up->mcr | UART_MCR_RTS);
-		serial_out(up, UART_LCR, cval);
+
+	if (termios->c_cflag & CRTSCTS && up->port.flags & UPF_HARD_FLOW) {
+		/* Enable AUTORTS and AUTOCTS */
+		up->efr |= UART_EFR_CTS | UART_EFR_RTS;
+
+		/* Ensure MCR RTS is asserted */
+		up->mcr |= UART_MCR_RTS;
+	} else {
+		/* Disable AUTORTS and AUTOCTS */
+		up->efr &= ~(UART_EFR_CTS | UART_EFR_RTS);
 	}
 
+	if (up->port.flags & UPF_SOFT_FLOW) {
+		/* clear SW control mode bits */
+		up->efr &= OMAP_UART_SW_CLR;
+
+		/*
+		 * IXON Flag:
+		 * Enable XON/XOFF flow control on input.
+		 * Receiver compares XON1, XOFF1.
+		 */
+		if (termios->c_iflag & IXON)
+			up->efr |= OMAP_UART_SW_RX;
+
+		/*
+		 * IXOFF Flag:
+		 * Enable XON/XOFF flow control on output.
+		 * Transmit XON1, XOFF1
+		 */
+		if (termios->c_iflag & IXOFF)
+			up->efr |= OMAP_UART_SW_TX;
+
+		/*
+		 * IXANY Flag:
+		 * Enable any character to restart output.
+		 * Operation resumes after receiving any
+		 * character after recognition of the XOFF character
+		 */
+		if (termios->c_iflag & IXANY)
+			up->mcr |= UART_MCR_XONANY;
+		else
+			up->mcr &= ~UART_MCR_XONANY;
+	}
+	serial_out(up, UART_MCR, up->mcr);
+	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
+	serial_out(up, UART_EFR, up->efr);
+	serial_out(up, UART_LCR, up->lcr);
+
 	serial_omap_set_mctrl(&up->port, up->port.mctrl);
-	/* Software Flow Control Configuration */
-	serial_omap_configure_xonxoff(up, termios);
 
 	spin_unlock_irqrestore(&up->port.lock, flags);
 	pm_runtime_mark_last_busy(up->dev);
@@ -987,6 +1053,7 @@ static void serial_omap_config_port(struct uart_port *port, int flags)
 	dev_dbg(up->port.dev, "serial_omap_config_port+%d\n",
 							up->port.line);
 	up->port.type = PORT_OMAP;
+	up->port.flags |= UPF_SOFT_FLOW | UPF_HARD_FLOW;
 }
 
 static int
@@ -1190,6 +1257,8 @@ static struct uart_ops serial_omap_pops = {
 	.get_mctrl	= serial_omap_get_mctrl,
 	.stop_tx	= serial_omap_stop_tx,
 	.start_tx	= serial_omap_start_tx,
+	.throttle	= serial_omap_throttle,
+	.unthrottle	= serial_omap_unthrottle,
 	.stop_rx	= serial_omap_stop_rx,
 	.enable_ms	= serial_omap_enable_ms,
 	.break_ctl	= serial_omap_break_ctl,

drivers/tty/serial/serial_core.c

@@ -610,27 +610,50 @@ static void uart_send_xchar(struct tty_struct *tty, char ch)
 static void uart_throttle(struct tty_struct *tty)
 {
 	struct uart_state *state = tty->driver_data;
+	struct uart_port *port = state->uart_port;
+	uint32_t mask = 0;
 
 	if (I_IXOFF(tty))
+		mask |= UPF_SOFT_FLOW;
+	if (tty->termios.c_cflag & CRTSCTS)
+		mask |= UPF_HARD_FLOW;
+
+	if (port->flags & mask) {
+		port->ops->throttle(port);
+		mask &= ~port->flags;
+	}
+
+	if (mask & UPF_SOFT_FLOW)
 		uart_send_xchar(tty, STOP_CHAR(tty));
 
-	if (tty->termios.c_cflag & CRTSCTS)
-		uart_clear_mctrl(state->uart_port, TIOCM_RTS);
+	if (mask & UPF_HARD_FLOW)
+		uart_clear_mctrl(port, TIOCM_RTS);
 }
 
 static void uart_unthrottle(struct tty_struct *tty)
 {
 	struct uart_state *state = tty->driver_data;
 	struct uart_port *port = state->uart_port;
+	uint32_t mask = 0;
 
-	if (I_IXOFF(tty)) {
+	if (I_IXOFF(tty))
+		mask |= UPF_SOFT_FLOW;
+	if (tty->termios.c_cflag & CRTSCTS)
+		mask |= UPF_HARD_FLOW;
+
+	if (port->flags & mask) {
+		port->ops->unthrottle(port);
+		mask &= ~port->flags;
+	}
+
+	if (mask & UPF_SOFT_FLOW) {
 		if (port->x_char)
 			port->x_char = 0;
 		else
 			uart_send_xchar(tty, START_CHAR(tty));
 	}
 
-	if (tty->termios.c_cflag & CRTSCTS)
+	if (mask & UPF_HARD_FLOW)
 		uart_set_mctrl(port, TIOCM_RTS);
 }
 
@@ -1214,9 +1237,22 @@ static void uart_set_termios(struct tty_struct *tty,
 						struct ktermios *old_termios)
 {
 	struct uart_state *state = tty->driver_data;
+	struct uart_port *uport = state->uart_port;
 	unsigned long flags;
 	unsigned int cflag = tty->termios.c_cflag;
+	unsigned int iflag_mask = IGNBRK|BRKINT|IGNPAR|PARMRK|INPCK;
+	bool sw_changed = false;
 
+	/*
+	 * Drivers doing software flow control also need to know
+	 * about changes to these input settings.
+	 */
+	if (uport->flags & UPF_SOFT_FLOW) {
+		iflag_mask |= IXANY|IXON|IXOFF;
+		sw_changed =
+		   tty->termios.c_cc[VSTART] != old_termios->c_cc[VSTART] ||
+		   tty->termios.c_cc[VSTOP] != old_termios->c_cc[VSTOP];
+	}
 
 	/*
 	 * These are the bits that are used to setup various
@@ -1224,11 +1260,11 @@ static void uart_set_termios(struct tty_struct *tty,
 	 * bits in c_cflag; c_[io]speed will always be set
 	 * appropriately by set_termios() in tty_ioctl.c
 	 */
-#define RELEVANT_IFLAG(iflag)	((iflag) & (IGNBRK|BRKINT|IGNPAR|PARMRK|INPCK))
 	if ((cflag ^ old_termios->c_cflag) == 0 &&
 	    tty->termios.c_ospeed == old_termios->c_ospeed &&
 	    tty->termios.c_ispeed == old_termios->c_ispeed &&
-	    RELEVANT_IFLAG(tty->termios.c_iflag ^ old_termios->c_iflag) == 0) {
+	    ((tty->termios.c_iflag ^ old_termios->c_iflag) & iflag_mask) == 0 &&
+	    !sw_changed) {
 		return;
 	}
 
@@ -1236,31 +1272,38 @@ static void uart_set_termios(struct tty_struct *tty,
 
 	/* Handle transition to B0 status */
 	if ((old_termios->c_cflag & CBAUD) && !(cflag & CBAUD))
-		uart_clear_mctrl(state->uart_port, TIOCM_RTS | TIOCM_DTR);
+		uart_clear_mctrl(uport, TIOCM_RTS | TIOCM_DTR);
 	/* Handle transition away from B0 status */
 	else if (!(old_termios->c_cflag & CBAUD) && (cflag & CBAUD)) {
 		unsigned int mask = TIOCM_DTR;
 		if (!(cflag & CRTSCTS) ||
 		    !test_bit(TTY_THROTTLED, &tty->flags))
 			mask |= TIOCM_RTS;
-		uart_set_mctrl(state->uart_port, mask);
+		uart_set_mctrl(uport, mask);
 	}
 
+	/*
+	 * If the port is doing h/w assisted flow control, do nothing.
+	 * We assume that tty->hw_stopped has never been set.
+	 */
+	if (uport->flags & UPF_HARD_FLOW)
+		return;
+
 	/* Handle turning off CRTSCTS */
 	if ((old_termios->c_cflag & CRTSCTS) && !(cflag & CRTSCTS)) {
-		spin_lock_irqsave(&state->uart_port->lock, flags);
+		spin_lock_irqsave(&uport->lock, flags);
 		tty->hw_stopped = 0;
 		__uart_start(tty);
-		spin_unlock_irqrestore(&state->uart_port->lock, flags);
+		spin_unlock_irqrestore(&uport->lock, flags);
 	}
 	/* Handle turning on CRTSCTS */
 	else if (!(old_termios->c_cflag & CRTSCTS) && (cflag & CRTSCTS)) {
-		spin_lock_irqsave(&state->uart_port->lock, flags);
-		if (!(state->uart_port->ops->get_mctrl(state->uart_port) & TIOCM_CTS)) {
+		spin_lock_irqsave(&uport->lock, flags);
+		if (!(uport->ops->get_mctrl(uport) & TIOCM_CTS)) {
 			tty->hw_stopped = 1;
-			state->uart_port->ops->stop_tx(state->uart_port);
+			uport->ops->stop_tx(uport);
 		}
-		spin_unlock_irqrestore(&state->uart_port->lock, flags);
+		spin_unlock_irqrestore(&uport->lock, flags);
 	}
 }
 

include/linux/serial_core.h

@@ -46,6 +46,8 @@ struct uart_ops {
 	unsigned int	(*get_mctrl)(struct uart_port *);
 	void		(*stop_tx)(struct uart_port *);
 	void		(*start_tx)(struct uart_port *);
+	void		(*throttle)(struct uart_port *);
+	void		(*unthrottle)(struct uart_port *);
 	void		(*send_xchar)(struct uart_port *, char ch);
 	void		(*stop_rx)(struct uart_port *);
 	void		(*enable_ms)(struct uart_port *);
@@ -163,6 +165,10 @@ struct uart_port {
 #define UPF_BUGGY_UART		((__force upf_t) (1 << 14))
 #define UPF_NO_TXEN_TEST	((__force upf_t) (1 << 15))
 #define UPF_MAGIC_MULTIPLIER	((__force upf_t) (1 << 16))
+/* Port has hardware-assisted h/w flow control (iow, auto-RTS *not* auto-CTS) */
+#define UPF_HARD_FLOW		((__force upf_t) (1 << 21))
+/* Port has hardware-assisted s/w flow control */
+#define UPF_SOFT_FLOW		((__force upf_t) (1 << 22))
 #define UPF_CONS_FLOW		((__force upf_t) (1 << 23))
 #define UPF_SHARE_IRQ		((__force upf_t) (1 << 24))
 #define UPF_EXAR_EFR		((__force upf_t) (1 << 25))