diff mbox series

[v5,2/3] tty: serial: use uart_port_tx() helper

Message ID 20221004104927.14361-3-jirislaby@kernel.org
State New
Headers show
Series tty: TX helpers | expand

Commit Message

Jiri Slaby Oct. 4, 2022, 10:49 a.m. UTC 
uart_port_tx() is a new helper to send characters to the device. Use it
in these drivers.

Cc: Tobias Klauser <tklauser@distanz.ch>
Cc: Richard Genoud <richard.genoud@gmail.com>
Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Claudiu Beznea <claudiu.beznea@microchip.com>
Cc: Vladimir Zapolskiy <vz@mleia.com>
Cc: Liviu Dudau <liviu.dudau@arm.com>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: NXP Linux Team <linux-imx@nxp.com>
Cc: "Andreas Färber" <afaerber@suse.de>
Cc: Manivannan Sadhasivam <mani@kernel.org>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
---

Notes:
    [v5] use bool pending in mcf_tx_chars() too [Ilpo]
    
    [v4] switch from DEFINE_UART_PORT_TX_HELPER() (helper generator) to
         uart_port_tx() (akin to wait_event())
    
    [v3] remove stray \n removal (Ilpo)

 drivers/tty/serial/altera_uart.c   | 29 ++++------------------
 drivers/tty/serial/atmel_serial.c  | 28 +++++----------------
 drivers/tty/serial/fsl_lpuart.c    | 30 ++++-------------------
 drivers/tty/serial/lantiq.c        | 36 +++------------------------
 drivers/tty/serial/lpc32xx_hs.c    | 33 +++----------------------
 drivers/tty/serial/mcf.c           | 34 ++++++--------------------
 drivers/tty/serial/mpc52xx_uart.c  | 39 +++---------------------------
 drivers/tty/serial/mps2-uart.c     | 26 +++-----------------
 drivers/tty/serial/mxs-auart.c     | 32 ++++++------------------
 drivers/tty/serial/owl-uart.c      | 32 +++---------------------
 drivers/tty/serial/sa1100.c        | 34 +++-----------------------
 drivers/tty/serial/vt8500_serial.c | 30 +++--------------------
 12 files changed, 60 insertions(+), 323 deletions(-)

Comments

Michael Walle Nov. 21, 2022, 8:27 p.m. UTC | #1 
From: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>

Hi Jiri,

> diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
> index bd07f79a2df9..a6b4d30c5888 100644
> --- a/drivers/tty/serial/atmel_serial.c
> +++ b/drivers/tty/serial/atmel_serial.c
> @@ -824,30 +824,14 @@ static void atmel_rx_chars(struct uart_port *port)
>   */
>  static void atmel_tx_chars(struct uart_port *port)
>  {
> -	struct circ_buf *xmit = &port->state->xmit;
>  	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
> +	bool pending;
> +	u8 ch;
>  
> -	if (port->x_char &&
> -	    (atmel_uart_readl(port, ATMEL_US_CSR) & ATMEL_US_TXRDY)) {
> -		atmel_uart_write_char(port, port->x_char);
> -		port->icount.tx++;
> -		port->x_char = 0;
> -	}
> -	if (uart_circ_empty(xmit) || uart_tx_stopped(port))
> -		return;
> -
> -	while (atmel_uart_readl(port, ATMEL_US_CSR) & ATMEL_US_TXRDY) {
> -		atmel_uart_write_char(port, xmit->buf[xmit->tail]);
> -		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
> -		port->icount.tx++;
> -		if (uart_circ_empty(xmit))
> -			break;
> -	}
> -
> -	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
> -		uart_write_wakeup(port);
> -
> -	if (!uart_circ_empty(xmit)) {
> +	pending = uart_port_tx(port, ch,
> +		atmel_uart_readl(port, ATMEL_US_CSR) & ATMEL_US_TXRDY,
> +		atmel_uart_write_char(port, ch));
> +	if (pending) {
>  		/* we still have characters to transmit, so we should continue
>  		 * transmitting them when TX is ready, regardless of
>  		 * mode or duplexity

This will break serial output for the userspace on my board
(arch/arm/boot/dts/lan966x-kontron-kswitch-d10-mmt*dts). The uart_port_tx()
helper will call __port->ops->stop_tx(__port) if uart_circ_chars_pending()
returns 0. But the code above, doesn't do that. In fact, removing the
stop_tx() call in the helper macro, will fix the console output.

Any ideas how to fix that?

-michael
Jiri Slaby Nov. 22, 2022, 7:02 a.m. UTC | #2 
Hi,

On 21. 11. 22, 21:27, Michael Walle wrote:
> This will break serial output for the userspace on my board
> (arch/arm/boot/dts/lan966x-kontron-kswitch-d10-mmt*dts). The uart_port_tx()
> helper will call __port->ops->stop_tx(__port) if uart_circ_chars_pending()
> returns 0. But the code above, doesn't do that. In fact, removing the
> stop_tx() call in the helper macro, will fix the console output.
> 
> Any ideas how to fix that?

Hm, so ATMEL_US_TXRDY is removed from tx_done_mask in stop_tx, but not 
added back in start_tx. So the tx interrupt is never handled (the tx 
tasklet is not scheduled to send the queue chars) in 
atmel_handle_transmit().

Any chance, the below fixes it?

diff --git a/drivers/tty/serial/atmel_serial.c 
b/drivers/tty/serial/atmel_serial.c
index 11bf2466390e..395370e0c77b 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -596,6 +596,8 @@ static void atmel_start_tx(struct uart_port *port)
                 /* re-enable PDC transmit */
                 atmel_uart_writel(port, ATMEL_PDC_PTCR, ATMEL_PDC_TXTEN);

+       atmel_port->tx_done_mask |= ATMEL_US_TXRDY;
+
         /* Enable interrupts */
         atmel_uart_writel(port, ATMEL_US_IER, atmel_port->tx_done_mask);


thanks,
Michael Walle Nov. 22, 2022, 8:18 a.m. UTC | #3 
Am 2022-11-22 09:09, schrieb Michael Walle:
> Hi,
> 
> Am 2022-11-22 08:02, schrieb Jiri Slaby:
>> On 21. 11. 22, 21:27, Michael Walle wrote:
>>> This will break serial output for the userspace on my board
>>> (arch/arm/boot/dts/lan966x-kontron-kswitch-d10-mmt*dts). The 
>>> uart_port_tx()
>>> helper will call __port->ops->stop_tx(__port) if 
>>> uart_circ_chars_pending()
>>> returns 0. But the code above, doesn't do that. In fact, removing the
>>> stop_tx() call in the helper macro, will fix the console output.
>>> 
>>> Any ideas how to fix that?
>> 
>> Hm, so ATMEL_US_TXRDY is removed from tx_done_mask in stop_tx, but not
>> added back in start_tx. So the tx interrupt is never handled (the tx
>> tasklet is not scheduled to send the queue chars) in
>> atmel_handle_transmit().
>> 
>> Any chance, the below fixes it?
>> 
>> diff --git a/drivers/tty/serial/atmel_serial.c
>> b/drivers/tty/serial/atmel_serial.c
>> index 11bf2466390e..395370e0c77b 100644
>> --- a/drivers/tty/serial/atmel_serial.c
>> +++ b/drivers/tty/serial/atmel_serial.c
>> @@ -596,6 +596,8 @@ static void atmel_start_tx(struct uart_port *port)
>>                 /* re-enable PDC transmit */
>>                 atmel_uart_writel(port, ATMEL_PDC_PTCR, 
>> ATMEL_PDC_TXTEN);
>> 
>> +       atmel_port->tx_done_mask |= ATMEL_US_TXRDY;
>> +
>>         /* Enable interrupts */
>>         atmel_uart_writel(port, ATMEL_US_IER, 
>> atmel_port->tx_done_mask);
>> 
>> 
>> thanks,
> 
> Unfortunately, that doesn't help. Btw, some characters are transmitted:
> 
> 
> [    6.219356] Key type dns_resolver registered
> [    6.223679] Registering SWP/SWPB emulation handler
> [    6.247530] Loading compiled-in X.509 certificates
> [    6.288467] Freeing unused kernel image (initmem) memory: 1024K
> [    6.297789] Run /init as init process
> WbSOROSOSOSOSOStarting linuxptp system clock synchronization: O
> 
> -michael

But you made me look at atmel_stop_tx() and there is this:

        /*
	* Disable the transmitter.
	* This is mandatory when DMA is used, otherwise the DMA buffer
	* is fully transmitted.
	*/
	atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXDIS);

Removing that write, will also fix the problem. Could it be, that
the transmit is still active (via DMA) but the driver will call
tx_stop() and then stop the transmission in the background?

-michael
Jiri Slaby Nov. 22, 2022, 8:25 a.m. UTC | #4 
On 22. 11. 22, 9:23, Jiri Slaby wrote:
> On 22. 11. 22, 9:18, Michael Walle wrote:
>> Am 2022-11-22 09:09, schrieb Michael Walle:
>>> Hi,
>>>
>>> Am 2022-11-22 08:02, schrieb Jiri Slaby:
>>>> On 21. 11. 22, 21:27, Michael Walle wrote:
>>>>> This will break serial output for the userspace on my board
>>>>> (arch/arm/boot/dts/lan966x-kontron-kswitch-d10-mmt*dts). The 
>>>>> uart_port_tx()
>>>>> helper will call __port->ops->stop_tx(__port) if 
>>>>> uart_circ_chars_pending()
>>>>> returns 0. But the code above, doesn't do that. In fact, removing the
>>>>> stop_tx() call in the helper macro, will fix the console output.
>>>>>
>>>>> Any ideas how to fix that?
>>>>
>>>> Hm, so ATMEL_US_TXRDY is removed from tx_done_mask in stop_tx, but not
>>>> added back in start_tx. So the tx interrupt is never handled (the tx
>>>> tasklet is not scheduled to send the queue chars) in
>>>> atmel_handle_transmit().
>>>>
>>>> Any chance, the below fixes it?
>>>>
>>>> diff --git a/drivers/tty/serial/atmel_serial.c
>>>> b/drivers/tty/serial/atmel_serial.c
>>>> index 11bf2466390e..395370e0c77b 100644
>>>> --- a/drivers/tty/serial/atmel_serial.c
>>>> +++ b/drivers/tty/serial/atmel_serial.c
>>>> @@ -596,6 +596,8 @@ static void atmel_start_tx(struct uart_port *port)
>>>>                 /* re-enable PDC transmit */
>>>>                 atmel_uart_writel(port, ATMEL_PDC_PTCR, 
>>>> ATMEL_PDC_TXTEN);
>>>>
>>>> +       atmel_port->tx_done_mask |= ATMEL_US_TXRDY;
>>>> +
>>>>         /* Enable interrupts */
>>>>         atmel_uart_writel(port, ATMEL_US_IER, 
>>>> atmel_port->tx_done_mask);
>>>>
>>>>
>>>> thanks,
>>>
>>> Unfortunately, that doesn't help. Btw, some characters are transmitted:
>>>
>>>
>>> [    6.219356] Key type dns_resolver registered
>>> [    6.223679] Registering SWP/SWPB emulation handler
>>> [    6.247530] Loading compiled-in X.509 certificates
>>> [    6.288467] Freeing unused kernel image (initmem) memory: 1024K
>>> [    6.297789] Run /init as init process
>>> WbSOROSOSOSOSOStarting linuxptp system clock synchronization: O
>>>
>>> -michael
>>
>> But you made me look at atmel_stop_tx() and there is this:
>>
>>         /*
>>      * Disable the transmitter.
>>      * This is mandatory when DMA is used, otherwise the DMA buffer
>>      * is fully transmitted.
>>      */
>>      atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXDIS);
>>
>> Removing that write, will also fix the problem. Could it be, that
>> the transmit is still active (via DMA) but the driver will call
>> tx_stop() and then stop the transmission in the background?
> 
> Yes, that was exactly the next step to try. The datasheet doesn't tell 
> much what happens when TXDIS is written while the characters are 
> transmitted.

Side note: your usart doesn't use dma. It's PIO (hence all that 
uart_tx_helper()). And the attached patch doesn't touch TXDIS for 
non-DMA case. I.e. it should transmit the final character (and nothing 
more).
Michael Walle Nov. 22, 2022, 9:13 a.m. UTC | #5 
Am 2022-11-22 09:25, schrieb Jiri Slaby:
> On 22. 11. 22, 9:23, Jiri Slaby wrote:
>> On 22. 11. 22, 9:18, Michael Walle wrote:
>>> Am 2022-11-22 09:09, schrieb Michael Walle:
>>>> Hi,
>>>> 
>>>> Am 2022-11-22 08:02, schrieb Jiri Slaby:
>>>>> On 21. 11. 22, 21:27, Michael Walle wrote:
>>>>>> This will break serial output for the userspace on my board
>>>>>> (arch/arm/boot/dts/lan966x-kontron-kswitch-d10-mmt*dts). The 
>>>>>> uart_port_tx()
>>>>>> helper will call __port->ops->stop_tx(__port) if 
>>>>>> uart_circ_chars_pending()
>>>>>> returns 0. But the code above, doesn't do that. In fact, removing 
>>>>>> the
>>>>>> stop_tx() call in the helper macro, will fix the console output.
>>>>>> 
>>>>>> Any ideas how to fix that?
>>>>> 
>>>>> Hm, so ATMEL_US_TXRDY is removed from tx_done_mask in stop_tx, but 
>>>>> not
>>>>> added back in start_tx. So the tx interrupt is never handled (the 
>>>>> tx
>>>>> tasklet is not scheduled to send the queue chars) in
>>>>> atmel_handle_transmit().
>>>>> 
>>>>> Any chance, the below fixes it?
>>>>> 
>>>>> diff --git a/drivers/tty/serial/atmel_serial.c
>>>>> b/drivers/tty/serial/atmel_serial.c
>>>>> index 11bf2466390e..395370e0c77b 100644
>>>>> --- a/drivers/tty/serial/atmel_serial.c
>>>>> +++ b/drivers/tty/serial/atmel_serial.c
>>>>> @@ -596,6 +596,8 @@ static void atmel_start_tx(struct uart_port 
>>>>> *port)
>>>>>                 /* re-enable PDC transmit */
>>>>>                 atmel_uart_writel(port, ATMEL_PDC_PTCR, 
>>>>> ATMEL_PDC_TXTEN);
>>>>> 
>>>>> +       atmel_port->tx_done_mask |= ATMEL_US_TXRDY;
>>>>> +
>>>>>         /* Enable interrupts */
>>>>>         atmel_uart_writel(port, ATMEL_US_IER, 
>>>>> atmel_port->tx_done_mask);
>>>>> 
>>>>> 
>>>>> thanks,
>>>> 
>>>> Unfortunately, that doesn't help. Btw, some characters are 
>>>> transmitted:
>>>> 
>>>> 
>>>> [    6.219356] Key type dns_resolver registered
>>>> [    6.223679] Registering SWP/SWPB emulation handler
>>>> [    6.247530] Loading compiled-in X.509 certificates
>>>> [    6.288467] Freeing unused kernel image (initmem) memory: 1024K
>>>> [    6.297789] Run /init as init process
>>>> WbSOROSOSOSOSOStarting linuxptp system clock synchronization: O
>>>> 
>>>> -michael
>>> 
>>> But you made me look at atmel_stop_tx() and there is this:
>>> 
>>>         /*
>>>      * Disable the transmitter.
>>>      * This is mandatory when DMA is used, otherwise the DMA buffer
>>>      * is fully transmitted.
>>>      */
>>>      atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXDIS);
>>> 
>>> Removing that write, will also fix the problem. Could it be, that
>>> the transmit is still active (via DMA) but the driver will call
>>> tx_stop() and then stop the transmission in the background?
>> 
>> Yes, that was exactly the next step to try. The datasheet doesn't tell 
>> much what happens when TXDIS is written while the characters are 
>> transmitted.
> 
> Side note: your usart doesn't use dma. It's PIO (hence all that
> uart_tx_helper()). And the attached patch doesn't touch TXDIS for
> non-DMA case. I.e. it should transmit the final character (and nothing
> more).

ok ;)

expect from "s/id_dma/is_dma/", this patch works. thanks!

-michael
diff mbox series

Patch

diff --git a/drivers/tty/serial/altera_uart.c b/drivers/tty/serial/altera_uart.c
index 82f2790de28d..316074bb23e9 100644
--- a/drivers/tty/serial/altera_uart.c
+++ b/drivers/tty/serial/altera_uart.c
@@ -247,31 +247,12 @@  static void altera_uart_rx_chars(struct uart_port *port)
 
 static void altera_uart_tx_chars(struct uart_port *port)
 {
-	struct circ_buf *xmit = &port->state->xmit;
-
-	if (port->x_char) {
-		/* Send special char - probably flow control */
-		altera_uart_writel(port, port->x_char, ALTERA_UART_TXDATA_REG);
-		port->x_char = 0;
-		port->icount.tx++;
-		return;
-	}
-
-	while (altera_uart_readl(port, ALTERA_UART_STATUS_REG) &
-	       ALTERA_UART_STATUS_TRDY_MSK) {
-		if (xmit->head == xmit->tail)
-			break;
-		altera_uart_writel(port, xmit->buf[xmit->tail],
-		       ALTERA_UART_TXDATA_REG);
-		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
-		port->icount.tx++;
-	}
-
-	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
-		uart_write_wakeup(port);
+	u8 ch;
 
-	if (uart_circ_empty(xmit))
-		altera_uart_stop_tx(port);
+	uart_port_tx(port, ch,
+		altera_uart_readl(port, ALTERA_UART_STATUS_REG) &
+		                ALTERA_UART_STATUS_TRDY_MSK,
+		altera_uart_writel(port, ch, ALTERA_UART_TXDATA_REG));
 }
 
 static irqreturn_t altera_uart_interrupt(int irq, void *data)
diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index bd07f79a2df9..a6b4d30c5888 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -824,30 +824,14 @@  static void atmel_rx_chars(struct uart_port *port)
  */
 static void atmel_tx_chars(struct uart_port *port)
 {
-	struct circ_buf *xmit = &port->state->xmit;
 	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
+	bool pending;
+	u8 ch;
 
-	if (port->x_char &&
-	    (atmel_uart_readl(port, ATMEL_US_CSR) & ATMEL_US_TXRDY)) {
-		atmel_uart_write_char(port, port->x_char);
-		port->icount.tx++;
-		port->x_char = 0;
-	}
-	if (uart_circ_empty(xmit) || uart_tx_stopped(port))
-		return;
-
-	while (atmel_uart_readl(port, ATMEL_US_CSR) & ATMEL_US_TXRDY) {
-		atmel_uart_write_char(port, xmit->buf[xmit->tail]);
-		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
-		port->icount.tx++;
-		if (uart_circ_empty(xmit))
-			break;
-	}
-
-	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
-		uart_write_wakeup(port);
-
-	if (!uart_circ_empty(xmit)) {
+	pending = uart_port_tx(port, ch,
+		atmel_uart_readl(port, ATMEL_US_CSR) & ATMEL_US_TXRDY,
+		atmel_uart_write_char(port, ch));
+	if (pending) {
 		/* we still have characters to transmit, so we should continue
 		 * transmitting them when TX is ready, regardless of
 		 * mode or duplexity
diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index 67fa113f77d4..d811eda1844e 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -742,32 +742,12 @@  static int lpuart32_poll_get_char(struct uart_port *port)
 
 static inline void lpuart_transmit_buffer(struct lpuart_port *sport)
 {
-	struct circ_buf *xmit = &sport->port.state->xmit;
-
-	if (sport->port.x_char) {
-		writeb(sport->port.x_char, sport->port.membase + UARTDR);
-		sport->port.icount.tx++;
-		sport->port.x_char = 0;
-		return;
-	}
-
-	if (lpuart_stopped_or_empty(&sport->port)) {
-		lpuart_stop_tx(&sport->port);
-		return;
-	}
-
-	while (!uart_circ_empty(xmit) &&
-		(readb(sport->port.membase + UARTTCFIFO) < sport->txfifo_size)) {
-		writeb(xmit->buf[xmit->tail], sport->port.membase + UARTDR);
-		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
-		sport->port.icount.tx++;
-	}
-
-	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
-		uart_write_wakeup(&sport->port);
+	struct uart_port *port = &sport->port;
+	u8 ch;
 
-	if (uart_circ_empty(xmit))
-		lpuart_stop_tx(&sport->port);
+	uart_port_tx(port, ch,
+		readb(port->membase + UARTTCFIFO) < sport->txfifo_size,
+		writeb(ch, port->membase + UARTDR));
 }
 
 static inline void lpuart32_transmit_buffer(struct lpuart_port *sport)
diff --git a/drivers/tty/serial/lantiq.c b/drivers/tty/serial/lantiq.c
index c892f3c7d1ab..a58e9277dfad 100644
--- a/drivers/tty/serial/lantiq.c
+++ b/drivers/tty/serial/lantiq.c
@@ -95,7 +95,6 @@ 
 #define ASCFSTAT_TXFFLMASK	0x3F00
 #define ASCFSTAT_TXFREEMASK	0x3F000000
 
-static void lqasc_tx_chars(struct uart_port *port);
 static struct ltq_uart_port *lqasc_port[MAXPORTS];
 static struct uart_driver lqasc_reg;
 
@@ -151,9 +150,12 @@  lqasc_start_tx(struct uart_port *port)
 {
 	unsigned long flags;
 	struct ltq_uart_port *ltq_port = to_ltq_uart_port(port);
+	u8 ch;
 
 	spin_lock_irqsave(&ltq_port->lock, flags);
-	lqasc_tx_chars(port);
+	uart_port_tx(port, ch,
+		lqasc_tx_ready(port),
+		writeb(ch, port->membase + LTQ_ASC_TBUF));
 	spin_unlock_irqrestore(&ltq_port->lock, flags);
 	return;
 }
@@ -226,36 +228,6 @@  lqasc_rx_chars(struct uart_port *port)
 	return 0;
 }
 
-static void
-lqasc_tx_chars(struct uart_port *port)
-{
-	struct circ_buf *xmit = &port->state->xmit;
-	if (uart_tx_stopped(port)) {
-		lqasc_stop_tx(port);
-		return;
-	}
-
-	while (lqasc_tx_ready(port)) {
-		if (port->x_char) {
-			writeb(port->x_char, port->membase + LTQ_ASC_TBUF);
-			port->icount.tx++;
-			port->x_char = 0;
-			continue;
-		}
-
-		if (uart_circ_empty(xmit))
-			break;
-
-		writeb(port->state->xmit.buf[port->state->xmit.tail],
-			port->membase + LTQ_ASC_TBUF);
-		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
-		port->icount.tx++;
-	}
-
-	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
-		uart_write_wakeup(port);
-}
-
 static irqreturn_t
 lqasc_tx_int(int irq, void *_port)
 {
diff --git a/drivers/tty/serial/lpc32xx_hs.c b/drivers/tty/serial/lpc32xx_hs.c
index ed47f4768338..b38fe4728c26 100644
--- a/drivers/tty/serial/lpc32xx_hs.c
+++ b/drivers/tty/serial/lpc32xx_hs.c
@@ -276,8 +276,6 @@  static void __serial_lpc32xx_rx(struct uart_port *port)
 	tty_flip_buffer_push(tport);
 }
 
-static void serial_lpc32xx_stop_tx(struct uart_port *port);
-
 static bool serial_lpc32xx_tx_ready(struct uart_port *port)
 {
 	u32 level = readl(LPC32XX_HSUART_LEVEL(port->membase));
@@ -287,34 +285,11 @@  static bool serial_lpc32xx_tx_ready(struct uart_port *port)
 
 static void __serial_lpc32xx_tx(struct uart_port *port)
 {
-	struct circ_buf *xmit = &port->state->xmit;
-
-	if (port->x_char) {
-		writel((u32)port->x_char, LPC32XX_HSUART_FIFO(port->membase));
-		port->icount.tx++;
-		port->x_char = 0;
-		return;
-	}
-
-	if (uart_circ_empty(xmit) || uart_tx_stopped(port))
-		goto exit_tx;
-
-	/* Transfer data */
-	while (serial_lpc32xx_tx_ready(port)) {
-		writel((u32) xmit->buf[xmit->tail],
-		       LPC32XX_HSUART_FIFO(port->membase));
-		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
-		port->icount.tx++;
-		if (uart_circ_empty(xmit))
-			break;
-	}
-
-	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
-		uart_write_wakeup(port);
+	u8 ch;
 
-exit_tx:
-	if (uart_circ_empty(xmit))
-		serial_lpc32xx_stop_tx(port);
+	uart_port_tx(port, ch,
+		serial_lpc32xx_tx_ready(port),
+		writel(ch, LPC32XX_HSUART_FIFO(port->membase)));
 }
 
 static irqreturn_t serial_lpc32xx_interrupt(int irq, void *dev_id)
diff --git a/drivers/tty/serial/mcf.c b/drivers/tty/serial/mcf.c
index b1cd9a76dd93..3239babe12a4 100644
--- a/drivers/tty/serial/mcf.c
+++ b/drivers/tty/serial/mcf.c
@@ -327,34 +327,16 @@  static void mcf_rx_chars(struct mcf_uart *pp)
 static void mcf_tx_chars(struct mcf_uart *pp)
 {
 	struct uart_port *port = &pp->port;
-	struct circ_buf *xmit = &port->state->xmit;
-
-	if (port->x_char) {
-		/* Send special char - probably flow control */
-		writeb(port->x_char, port->membase + MCFUART_UTB);
-		port->x_char = 0;
-		port->icount.tx++;
-		return;
-	}
-
-	while (readb(port->membase + MCFUART_USR) & MCFUART_USR_TXREADY) {
-		if (uart_circ_empty(xmit))
-			break;
-		writeb(xmit->buf[xmit->tail], port->membase + MCFUART_UTB);
-		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE -1);
-		port->icount.tx++;
-	}
+	bool pending;
+	u8 ch;
 
-	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
-		uart_write_wakeup(port);
+	pending = uart_port_tx(port, ch,
+		readb(port->membase + MCFUART_USR) & MCFUART_USR_TXREADY,
+		writeb(ch, port->membase + MCFUART_UTB));
 
-	if (uart_circ_empty(xmit)) {
-		mcf_stop_tx(port);
-		/* Disable TX to negate RTS automatically */
-		if (port->rs485.flags & SER_RS485_ENABLED)
-			writeb(MCFUART_UCR_TXDISABLE,
-				port->membase + MCFUART_UCR);
-	}
+	/* Disable TX to negate RTS automatically */
+	if (!pending && (port->rs485.flags & SER_RS485_ENABLED))
+		writeb(MCFUART_UCR_TXDISABLE, port->membase + MCFUART_UCR);
 }
 
 /****************************************************************************/
diff --git a/drivers/tty/serial/mpc52xx_uart.c b/drivers/tty/serial/mpc52xx_uart.c
index 73362d4bc45d..384ca195e3d5 100644
--- a/drivers/tty/serial/mpc52xx_uart.c
+++ b/drivers/tty/serial/mpc52xx_uart.c
@@ -1428,42 +1428,11 @@  mpc52xx_uart_int_rx_chars(struct uart_port *port)
 static inline bool
 mpc52xx_uart_int_tx_chars(struct uart_port *port)
 {
-	struct circ_buf *xmit = &port->state->xmit;
-
-	/* Process out of band chars */
-	if (port->x_char) {
-		psc_ops->write_char(port, port->x_char);
-		port->icount.tx++;
-		port->x_char = 0;
-		return true;
-	}
-
-	/* Nothing to do ? */
-	if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
-		mpc52xx_uart_stop_tx(port);
-		return false;
-	}
-
-	/* Send chars */
-	while (psc_ops->raw_tx_rdy(port)) {
-		psc_ops->write_char(port, xmit->buf[xmit->tail]);
-		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
-		port->icount.tx++;
-		if (uart_circ_empty(xmit))
-			break;
-	}
-
-	/* Wake up */
-	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
-		uart_write_wakeup(port);
-
-	/* Maybe we're done after all */
-	if (uart_circ_empty(xmit)) {
-		mpc52xx_uart_stop_tx(port);
-		return false;
-	}
+	u8 ch;
 
-	return true;
+	return uart_port_tx(port, ch,
+		psc_ops->raw_tx_rdy(port),
+		psc_ops->write_char(port, ch));
 }
 
 static irqreturn_t
diff --git a/drivers/tty/serial/mps2-uart.c b/drivers/tty/serial/mps2-uart.c
index 2e3e6cf16817..860d161fa594 100644
--- a/drivers/tty/serial/mps2-uart.c
+++ b/drivers/tty/serial/mps2-uart.c
@@ -129,29 +129,11 @@  static void mps2_uart_stop_tx(struct uart_port *port)
 
 static void mps2_uart_tx_chars(struct uart_port *port)
 {
-	struct circ_buf *xmit = &port->state->xmit;
-
-	while (!(mps2_uart_read8(port, UARTn_STATE) & UARTn_STATE_TX_FULL)) {
-		if (port->x_char) {
-			mps2_uart_write8(port, port->x_char, UARTn_DATA);
-			port->x_char = 0;
-			port->icount.tx++;
-			continue;
-		}
-
-		if (uart_circ_empty(xmit) || uart_tx_stopped(port))
-			break;
-
-		mps2_uart_write8(port, xmit->buf[xmit->tail], UARTn_DATA);
-		xmit->tail = (xmit->tail + 1) % UART_XMIT_SIZE;
-		port->icount.tx++;
-	}
-
-	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
-		uart_write_wakeup(port);
+	u8 ch;
 
-	if (uart_circ_empty(xmit))
-		mps2_uart_stop_tx(port);
+	uart_port_tx(port, ch,
+		mps2_uart_tx_empty(port),
+		mps2_uart_write8(port, ch, UARTn_DATA));
 }
 
 static void mps2_uart_start_tx(struct uart_port *port)
diff --git a/drivers/tty/serial/mxs-auart.c b/drivers/tty/serial/mxs-auart.c
index d21a4f3ef2fe..ef6e7bb6105c 100644
--- a/drivers/tty/serial/mxs-auart.c
+++ b/drivers/tty/serial/mxs-auart.c
@@ -569,6 +569,8 @@  static int mxs_auart_dma_tx(struct mxs_auart_port *s, int size)
 static void mxs_auart_tx_chars(struct mxs_auart_port *s)
 {
 	struct circ_buf *xmit = &s->port.state->xmit;
+	bool pending;
+	u8 ch;
 
 	if (auart_dma_enabled(s)) {
 		u32 i = 0;
@@ -603,31 +605,13 @@  static void mxs_auart_tx_chars(struct mxs_auart_port *s)
 		return;
 	}
 
-
-	while (!(mxs_read(s, REG_STAT) & AUART_STAT_TXFF)) {
-		if (s->port.x_char) {
-			s->port.icount.tx++;
-			mxs_write(s->port.x_char, s, REG_DATA);
-			s->port.x_char = 0;
-			continue;
-		}
-		if (!uart_circ_empty(xmit) && !uart_tx_stopped(&s->port)) {
-			s->port.icount.tx++;
-			mxs_write(xmit->buf[xmit->tail], s, REG_DATA);
-			xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
-		} else
-			break;
-	}
-	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
-		uart_write_wakeup(&s->port);
-
-	if (uart_circ_empty(&(s->port.state->xmit)))
-		mxs_clr(AUART_INTR_TXIEN, s, REG_INTR);
-	else
+	pending = uart_port_tx(&s->port, ch,
+		!(mxs_read(s, REG_STAT) & AUART_STAT_TXFF),
+		mxs_write(ch, s, REG_DATA));
+	if (pending)
 		mxs_set(AUART_INTR_TXIEN, s, REG_INTR);
-
-	if (uart_tx_stopped(&s->port))
-		mxs_auart_stop_tx(&s->port);
+	else
+		mxs_clr(AUART_INTR_TXIEN, s, REG_INTR);
 }
 
 static void mxs_auart_rx_char(struct mxs_auart_port *s)
diff --git a/drivers/tty/serial/owl-uart.c b/drivers/tty/serial/owl-uart.c
index fde39cc1145d..e99970a9437f 100644
--- a/drivers/tty/serial/owl-uart.c
+++ b/drivers/tty/serial/owl-uart.c
@@ -181,35 +181,11 @@  static void owl_uart_start_tx(struct uart_port *port)
 
 static void owl_uart_send_chars(struct uart_port *port)
 {
-	struct circ_buf *xmit = &port->state->xmit;
-	unsigned int ch;
-
-	if (port->x_char) {
-		while (!(owl_uart_read(port, OWL_UART_STAT) & OWL_UART_STAT_TFFU))
-			cpu_relax();
-		owl_uart_write(port, port->x_char, OWL_UART_TXDAT);
-		port->icount.tx++;
-		port->x_char = 0;
-	}
-
-	if (uart_tx_stopped(port))
-		return;
-
-	while (!(owl_uart_read(port, OWL_UART_STAT) & OWL_UART_STAT_TFFU)) {
-		if (uart_circ_empty(xmit))
-			break;
+	u8 ch;
 
-		ch = xmit->buf[xmit->tail];
-		owl_uart_write(port, ch, OWL_UART_TXDAT);
-		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
-		port->icount.tx++;
-	}
-
-	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
-		uart_write_wakeup(port);
-
-	if (uart_circ_empty(xmit))
-		owl_uart_stop_tx(port);
+	uart_port_tx(port, ch,
+		!(owl_uart_read(port, OWL_UART_STAT) & OWL_UART_STAT_TFFU),
+		owl_uart_write(port, ch, OWL_UART_TXDAT));
 }
 
 static void owl_uart_receive_chars(struct uart_port *port)
diff --git a/drivers/tty/serial/sa1100.c b/drivers/tty/serial/sa1100.c
index dd9e3253cab4..55107bbc00ce 100644
--- a/drivers/tty/serial/sa1100.c
+++ b/drivers/tty/serial/sa1100.c
@@ -228,14 +228,7 @@  sa1100_rx_chars(struct sa1100_port *sport)
 
 static void sa1100_tx_chars(struct sa1100_port *sport)
 {
-	struct circ_buf *xmit = &sport->port.state->xmit;
-
-	if (sport->port.x_char) {
-		UART_PUT_CHAR(sport, sport->port.x_char);
-		sport->port.icount.tx++;
-		sport->port.x_char = 0;
-		return;
-	}
+	u8 ch;
 
 	/*
 	 * Check the modem control lines before
@@ -243,28 +236,9 @@  static void sa1100_tx_chars(struct sa1100_port *sport)
 	 */
 	sa1100_mctrl_check(sport);
 
-	if (uart_circ_empty(xmit) || uart_tx_stopped(&sport->port)) {
-		sa1100_stop_tx(&sport->port);
-		return;
-	}
-
-	/*
-	 * Tried using FIFO (not checking TNF) for fifo fill:
-	 * still had the '4 bytes repeated' problem.
-	 */
-	while (UART_GET_UTSR1(sport) & UTSR1_TNF) {
-		UART_PUT_CHAR(sport, xmit->buf[xmit->tail]);
-		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
-		sport->port.icount.tx++;
-		if (uart_circ_empty(xmit))
-			break;
-	}
-
-	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
-		uart_write_wakeup(&sport->port);
-
-	if (uart_circ_empty(xmit))
-		sa1100_stop_tx(&sport->port);
+	uart_port_tx(&sport->port, ch,
+			UART_GET_UTSR1(sport) & UTSR1_TNF,
+			UART_PUT_CHAR(sport, ch));
 }
 
 static irqreturn_t sa1100_int(int irq, void *dev_id)
diff --git a/drivers/tty/serial/vt8500_serial.c b/drivers/tty/serial/vt8500_serial.c
index 10fbdb09965f..deedb6513160 100644
--- a/drivers/tty/serial/vt8500_serial.c
+++ b/drivers/tty/serial/vt8500_serial.c
@@ -196,33 +196,11 @@  static unsigned int vt8500_tx_empty(struct uart_port *port)
 
 static void handle_tx(struct uart_port *port)
 {
-	struct circ_buf *xmit = &port->state->xmit;
+	u8 ch;
 
-	if (port->x_char) {
-		writeb(port->x_char, port->membase + VT8500_TXFIFO);
-		port->icount.tx++;
-		port->x_char = 0;
-	}
-	if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
-		vt8500_stop_tx(port);
-		return;
-	}
-
-	while (vt8500_tx_empty(port)) {
-		if (uart_circ_empty(xmit))
-			break;
-
-		writeb(xmit->buf[xmit->tail], port->membase + VT8500_TXFIFO);
-
-		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
-		port->icount.tx++;
-	}
-
-	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
-		uart_write_wakeup(port);
-
-	if (uart_circ_empty(xmit))
-		vt8500_stop_tx(port);
+	uart_port_tx(port, ch,
+		vt8500_tx_empty(port),
+		writeb(ch, port->membase + VT8500_TXFIFO));
 }
 
 static void vt8500_start_tx(struct uart_port *port)