serial: 8250: omap: restore registers on shutdown

If DMA is active during a shutdown, a delayed restore of the registers may be pending. The restore must be performed after the DMA is stopped, otherwise the delayed restore remains pending and will fire upon the first DMA TX complete of a totally different serial session.

Signed-off-by John Ogness <[email protected]>

---
 drivers/tty/serial/8250/8250_omap.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

drivers/tty/serial/8250/8250_omap.c +0 -0

index 5b39892..25f6255 100644
@@ -657,9 +657,15 @@ static void omap_8250_shutdown(struct uart_port *port)
 	up->ier = 0;

drivers/tty/serial/8250/8250_omap.c +2 -0

+	}
+
 	/*
 	 * Disable break condition and FIFOs
 	 */

Hi John,

I was never really a fan of the deferred set_termios(); I think it's more appropriate to wait for tx dma to complete in omap_8250_set_termios().

Quoted 1 line · * Peter Hurley | 2015-07-30 20:51:10 [-0400]:

Hi John,

Hi Peter,

Quoted 3 lines

I was never really a fan of the deferred set_termios(); I think it's more appropriate to wait for tx dma to complete in omap_8250_set_termios().

So you want something like this? This was only compile + boot tested (without triggering the corner case) and I know that 8250.h piece has to go in a separated patch (as requested in 2/3 of this series). Just checking if this is what you had in mind.

drivers/tty/serial/8250/8250.h +0 -0

index c43f74c53cd9..a407757dcecc 100644

drivers/tty/serial/8250/8250.h +0 -0

 struct old_serial_port {

drivers/tty/serial/8250/8250_omap.c +9 -13

index d9a37191a1ae..12249125a218 100644
@@ -100,9 +100,9 @@ struct omap8250_priv {
 	u8 wer;
 	u8 xon;
 	u8 xoff;
-	u8 delayed_restore;
 	u16 quot;
 
+	wait_queue_head_t termios_wait;
 	bool is_suspending;
 	int wakeirq;
 	int wakeups_enabled;

@@ -256,18 +256,6 @@ static void omap8250_update_mdr1(struct uart_8250_port *up,
 static void omap8250_restore_regs(struct uart_8250_port *up)
 {
 	struct omap8250_priv *priv = up->port.private_data;
-	struct uart_8250_dma	*dma = up->dma;
-
-	if (dma && dma->tx_running) {
-		/*
-		 * TCSANOW requests the change to occur immediately however if
-		 * we have a TX-DMA operation in progress then it has been
-		 * observed that it might stall and never complete. Therefore we
-		 * delay DMA completes to prevent this hang from happen.
-		 */
-		priv->delayed_restore = 1;
-		return;
-	}
 
 	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
 	serial_out(up, UART_EFR, UART_EFR_ECB);

@@ -309,6 +297,7 @@ static void omap8250_restore_regs(struct uart_8250_port *up)
 	up->port.ops->set_mctrl(&up->port, up->port.mctrl);
 }
 
+static void omap_8250_dma_tx_complete(void *param);
 /*
  * OMAP can use "CLK / (16 or 13) / div" for baud rate. And then we have have
  * some differences in how we want to handle flow control.

@@ -322,6 +311,7 @@ static void omap_8250_set_termios(struct uart_port *port,
 	struct omap8250_priv *priv = up->port.private_data;
 	unsigned char cval = 0;
 	unsigned int baud;
+	unsigned int complete_dma = 0;
 
 	switch (termios->c_cflag & CSIZE) {
 	case CS5:

@@ -473,6 +463,25 @@ static void omap_8250_set_termios(struct uart_port *port,
 		if (termios->c_iflag & IXANY)
 			up->mcr |= UART_MCR_XONANY;
 	}
+
+	if (up->dma && up->dma->tx_running) {
+		struct uart_8250_dma	*dma = up->dma;
+
+		/*
+		 * TCSANOW requests the change to occur immediately however if

drivers/tty/serial/8250/8250_omap.c +13 -6

+		spin_lock_irq(&up->port.lock);
+		complete_dma = 1;
+	}
 	omap8250_restore_regs(up);
 
 	spin_unlock_irq(&up->port.lock);

@@ -488,6 +497,8 @@ static void omap_8250_set_termios(struct uart_port *port,
 	/* Don't rewrite B0 */
 	if (tty_termios_baud_rate(termios))
 		tty_termios_encode_baud_rate(termios, baud, baud);
+	if (complete_dma)
+		omap_8250_dma_tx_complete(up);
 }
 
 /* same as 8250 except that we may have extra flow bits set in EFR */

@@ -869,17 +880,18 @@ static void omap_8250_dma_tx_complete(void *param)
 
 	spin_lock_irqsave(&p->port.lock, flags);
 
+	if (dma->tx_running == 2) {
+		dma->tx_running = 3;
+		wake_up(&priv->termios_wait);
+		goto out;
+	}
+
 	dma->tx_running = 0;
 
 	xmit->tail += dma->tx_size;
 	xmit->tail &= UART_XMIT_SIZE - 1;
 	p->port.icount.tx += dma->tx_size;
 
-	if (priv->delayed_restore) {
-		priv->delayed_restore = 0;
-		omap8250_restore_regs(p);
-	}
-
 	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
 		uart_write_wakeup(&p->port);
 

@@ -899,7 +911,7 @@ static void omap_8250_dma_tx_complete(void *param)
 		p->ier |= UART_IER_THRI;
 		serial_port_out(&p->port, UART_IER, p->ier);
 	}
-
+out:
 	spin_unlock_irqrestore(&p->port.lock, flags);
 }
 

@@ -1216,6 +1228,7 @@ static int omap8250_probe(struct platform_device *pdev)
 			priv->omap8250_dma.rx_size = RX_TRIGGER;
 			priv->omap8250_dma.rxconf.src_maxburst = RX_TRIGGER;
 			priv->omap8250_dma.txconf.dst_maxburst = TX_TRIGGER;
+			init_waitqueue_head(&priv->termios_wait);
 
 			if (of_machine_is_compatible("ti,am33xx"))
 				priv->habit |= OMAP_DMA_TX_KICK;

Sebastian

Hi Sebastian,

Quoted 66 lines

struct old_serial_port {

drivers/tty/serial/8250/8250_omap.c +14 -13

index d9a37191a1ae..12249125a218 100644
@@ -100,9 +100,9 @@ struct omap8250_priv {
 	u8 wer;
 	u8 xon;
 	u8 xoff;
-	u8 delayed_restore;
 	u16 quot;
 
+	wait_queue_head_t termios_wait;
 	bool is_suspending;
 	int wakeirq;
 	int wakeups_enabled;

@@ -256,18 +256,6 @@ static void omap8250_update_mdr1(struct uart_8250_port *up,
 static void omap8250_restore_regs(struct uart_8250_port *up)
 {
 	struct omap8250_priv *priv = up->port.private_data;
-	struct uart_8250_dma	*dma = up->dma;
-
-	if (dma && dma->tx_running) {
-		/*
-		 * TCSANOW requests the change to occur immediately however if
-		 * we have a TX-DMA operation in progress then it has been
-		 * observed that it might stall and never complete. Therefore we
-		 * delay DMA completes to prevent this hang from happen.
-		 */
-		priv->delayed_restore = 1;
-		return;
-	}
 
 	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
 	serial_out(up, UART_EFR, UART_EFR_ECB);

@@ -309,6 +297,7 @@ static void omap8250_restore_regs(struct uart_8250_port *up)
 	up->port.ops->set_mctrl(&up->port, up->port.mctrl);
 }
 
+static void omap_8250_dma_tx_complete(void *param);
 /*
  * OMAP can use "CLK / (16 or 13) / div" for baud rate. And then we have have
  * some differences in how we want to handle flow control.

@@ -322,6 +311,7 @@ static void omap_8250_set_termios(struct uart_port *port,
 	struct omap8250_priv *priv = up->port.private_data;
 	unsigned char cval = 0;
 	unsigned int baud;
+	unsigned int complete_dma = 0;
 
 	switch (termios->c_cflag & CSIZE) {
 	case CS5:

@@ -473,6 +463,25 @@ static void omap_8250_set_termios(struct uart_port *port,
 		if (termios->c_iflag & IXANY)
 			up->mcr |= UART_MCR_XONANY;
 	}
+
+	if (up->dma && up->dma->tx_running) {
+		struct uart_8250_dma	*dma = up->dma;
+
+		/*
+		 * TCSANOW requests the change to occur immediately however if
+		 * we have a TX-DMA operation in progress then it has been
+		 * observed that it might stall and never complete. Therefore we
+		 * wait until DMA completes to prevent this hang from happen.
+		 */
+

drivers/tty/serial/8250/8250_omap.c static void omap_8250_set_termios(struct uart_port *port, · line 481

Quoted 5 lines

drivers/tty/serial/8250/8250_omap.c +5 -0

+		dma->tx_running = 2;
+
+		spin_unlock_irq(&up->port.lock);
+		wait_event(priv->termios_wait,
+			   dma->tx_running == 3);

Doesn't the dmaengine api offer a race-free way to wait for pending tx dma to complete?

Maybe we could wrap that in the 8250 dma api?

Regards,
Peter Hurley

Quoted 54 lines

drivers/tty/serial/8250/8250_omap.c +13 -6

+		spin_lock_irq(&up->port.lock);
+		complete_dma = 1;
+	}
 	omap8250_restore_regs(up);
 
 	spin_unlock_irq(&up->port.lock);

@@ -488,6 +497,8 @@ static void omap_8250_set_termios(struct uart_port *port,
 	/* Don't rewrite B0 */
 	if (tty_termios_baud_rate(termios))
 		tty_termios_encode_baud_rate(termios, baud, baud);
+	if (complete_dma)
+		omap_8250_dma_tx_complete(up);
 }
 
 /* same as 8250 except that we may have extra flow bits set in EFR */

@@ -869,17 +880,18 @@ static void omap_8250_dma_tx_complete(void *param)
 
 	spin_lock_irqsave(&p->port.lock, flags);
 
+	if (dma->tx_running == 2) {
+		dma->tx_running = 3;
+		wake_up(&priv->termios_wait);
+		goto out;
+	}
+
 	dma->tx_running = 0;
 
 	xmit->tail += dma->tx_size;
 	xmit->tail &= UART_XMIT_SIZE - 1;
 	p->port.icount.tx += dma->tx_size;
 
-	if (priv->delayed_restore) {
-		priv->delayed_restore = 0;
-		omap8250_restore_regs(p);
-	}
-
 	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
 		uart_write_wakeup(&p->port);
 

@@ -899,7 +911,7 @@ static void omap_8250_dma_tx_complete(void *param)
 		p->ier |= UART_IER_THRI;
 		serial_port_out(&p->port, UART_IER, p->ier);
 	}
-
+out:
 	spin_unlock_irqrestore(&p->port.lock, flags);
 }
 

@@ -1216,6 +1228,7 @@ static int omap8250_probe(struct platform_device *pdev)
 			priv->omap8250_dma.rx_size = RX_TRIGGER;
 			priv->omap8250_dma.rxconf.src_maxburst = RX_TRIGGER;
 			priv->omap8250_dma.txconf.dst_maxburst = TX_TRIGGER;
+			init_waitqueue_head(&priv->termios_wait);
 

drivers/tty/serial/8250/8250_omap.c static int omap8250_probe(struct platform_device *pdev) · line 1234

Quoted 3 lines

drivers/tty/serial/8250/8250_omap.c +0 -0

 			if (of_machine_is_compatible("ti,am33xx"))
 				priv->habit |= OMAP_DMA_TX_KICK;

Quoted 1 line · Peter Hurley

Hi Sebastian,

Hi Peter,

Quoted 66 lines

Quoted 66 lines

struct old_serial_port {

drivers/tty/serial/8250/8250_omap.c +14 -13

index d9a37191a1ae..12249125a218 100644
@@ -100,9 +100,9 @@ struct omap8250_priv {
 	u8 wer;
 	u8 xon;
 	u8 xoff;
-	u8 delayed_restore;
 	u16 quot;
 
+	wait_queue_head_t termios_wait;
 	bool is_suspending;
 	int wakeirq;
 	int wakeups_enabled;

@@ -256,18 +256,6 @@ static void omap8250_update_mdr1(struct uart_8250_port *up,
 static void omap8250_restore_regs(struct uart_8250_port *up)
 {
 	struct omap8250_priv *priv = up->port.private_data;
-	struct uart_8250_dma	*dma = up->dma;
-
-	if (dma && dma->tx_running) {
-		/*
-		 * TCSANOW requests the change to occur immediately however if
-		 * we have a TX-DMA operation in progress then it has been
-		 * observed that it might stall and never complete. Therefore we
-		 * delay DMA completes to prevent this hang from happen.
-		 */
-		priv->delayed_restore = 1;
-		return;
-	}
 
 	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
 	serial_out(up, UART_EFR, UART_EFR_ECB);

@@ -309,6 +297,7 @@ static void omap8250_restore_regs(struct uart_8250_port *up)
 	up->port.ops->set_mctrl(&up->port, up->port.mctrl);
 }
 
+static void omap_8250_dma_tx_complete(void *param);
 /*
  * OMAP can use "CLK / (16 or 13) / div" for baud rate. And then we have have
  * some differences in how we want to handle flow control.

@@ -322,6 +311,7 @@ static void omap_8250_set_termios(struct uart_port *port,
 	struct omap8250_priv *priv = up->port.private_data;
 	unsigned char cval = 0;
 	unsigned int baud;
+	unsigned int complete_dma = 0;
 
 	switch (termios->c_cflag & CSIZE) {
 	case CS5:

@@ -473,6 +463,25 @@ static void omap_8250_set_termios(struct uart_port *port,
 		if (termios->c_iflag & IXANY)
 			up->mcr |= UART_MCR_XONANY;
 	}
+
+	if (up->dma && up->dma->tx_running) {
+		struct uart_8250_dma	*dma = up->dma;
+
+		/*
+		 * TCSANOW requests the change to occur immediately however if
+		 * we have a TX-DMA operation in progress then it has been
+		 * observed that it might stall and never complete. Therefore we
+		 * wait until DMA completes to prevent this hang from happen.
+		 */
+

Quoted 8 lines

drivers/tty/serial/8250/8250_omap.c static void omap_8250_set_termios(struct uart_port *port, · line 481

Quoted 5 lines

drivers/tty/serial/8250/8250_omap.c +5 -0

+		dma->tx_running = 2;
+
+		spin_unlock_irq(&up->port.lock);
+		wait_event(priv->termios_wait,
+			   dma->tx_running == 3);

Doesn't the dmaengine api offer a race-free way to wait for pending tx dma to complete?

Not that I know of. You still need to ensure that once that DMA completed, nobody triggers another TX transfer before you do what you planned. This is ensures by the tx_running != 0 and the spin lock.

Quoted 1 line

Maybe we could wrap that in the 8250 dma api?

You mean a function in 8250-dma API which does what I did just here with the wait_event() and the wake_up in the callback? That way I could move the termios_wait into the dma struct instead of keeping in the omap specific part. I am also not sure if OMAP is the only one that may hang here or the other people just didn't notice it yet.

Quoted 54 lines

Quoted 54 lines

drivers/tty/serial/8250/8250_omap.c +13 -6

+		spin_lock_irq(&up->port.lock);
+		complete_dma = 1;
+	}
 	omap8250_restore_regs(up);
 
 	spin_unlock_irq(&up->port.lock);

@@ -488,6 +497,8 @@ static void omap_8250_set_termios(struct uart_port *port,
 	/* Don't rewrite B0 */
 	if (tty_termios_baud_rate(termios))
 		tty_termios_encode_baud_rate(termios, baud, baud);
+	if (complete_dma)
+		omap_8250_dma_tx_complete(up);
 }
 
 /* same as 8250 except that we may have extra flow bits set in EFR */

@@ -869,17 +880,18 @@ static void omap_8250_dma_tx_complete(void *param)
 
 	spin_lock_irqsave(&p->port.lock, flags);
 
+	if (dma->tx_running == 2) {
+		dma->tx_running = 3;
+		wake_up(&priv->termios_wait);
+		goto out;
+	}
+
 	dma->tx_running = 0;
 
 	xmit->tail += dma->tx_size;
 	xmit->tail &= UART_XMIT_SIZE - 1;
 	p->port.icount.tx += dma->tx_size;
 
-	if (priv->delayed_restore) {
-		priv->delayed_restore = 0;
-		omap8250_restore_regs(p);
-	}
-
 	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
 		uart_write_wakeup(&p->port);
 

@@ -899,7 +911,7 @@ static void omap_8250_dma_tx_complete(void *param)
 		p->ier |= UART_IER_THRI;
 		serial_port_out(&p->port, UART_IER, p->ier);
 	}
-
+out:
 	spin_unlock_irqrestore(&p->port.lock, flags);
 }
 

@@ -1216,6 +1228,7 @@ static int omap8250_probe(struct platform_device *pdev)
 			priv->omap8250_dma.rx_size = RX_TRIGGER;
 			priv->omap8250_dma.rxconf.src_maxburst = RX_TRIGGER;
 			priv->omap8250_dma.txconf.dst_maxburst = TX_TRIGGER;
+			init_waitqueue_head(&priv->termios_wait);
 

Quoted 3 lines

drivers/tty/serial/8250/8250_omap.c static int omap8250_probe(struct platform_device *pdev) · line 1234

Quoted 3 lines

drivers/tty/serial/8250/8250_omap.c +0 -0

 			if (of_machine_is_compatible("ti,am33xx"))
 				priv->habit |= OMAP_DMA_TX_KICK;

Sebastian

Quoted 5 lines

You mean a function in 8250-dma API which does what I did just here with the wait_event() and the wake_up in the callback? That way I could move the termios_wait into the dma struct instead of keeping in the omap specific part. I am also not sure if OMAP is the only one that may hang here or the other people just didn't notice it yet.

Exactly; and we need to fix DMA wrt x_char anyway.

Going back to the dmaengine api, I think something like this might work (as a first approximation):

	dma_sync_wait(dma->txchan, dma->tx_cookie);
	dmaengine_pause(dma->txchan);

	/* remainder of set_termios */

	dmaengine_resume(dma->txchan);

We could require 8250 core dma to support pause/resume.

Quoted 11 lines · Peter Hurley

Quoted 5 lines

You mean a function in 8250-dma API which does what I did just here with the wait_event() and the wake_up in the callback? That way I could move the termios_wait into the dma struct instead of keeping in the omap specific part. I am also not sure if OMAP is the only one that may hang here or the other people just didn't notice it yet.

Exactly; and we need to fix DMA wrt x_char anyway.

Going back to the dmaengine api, I think something like this might work (as a first approximation):

Quoted 8 lines

	dma_sync_wait(dma->txchan, dma->tx_cookie);
	dmaengine_pause(dma->txchan);

	/* remainder of set_termios */

	dmaengine_resume(dma->txchan);

We could require 8250 core dma to support pause/resume.

I would prefer the waitqueue approach.
You can't do this while holding the port lock. The lock is taken with irqs off so may not see the transfer completing.
Why do you pause the channel? It may not work without an active descriptor and a start without "resume" should work. Also you must ensure that DMA's complete callback does not start another transfer if there is something queued up (that is why I had the tx_running dance). I am not sure if a transfer that is active and then paused will not trigger the hang bug if we change the termios in between.

Hi Sebastian,

Quoted 22 lines · Peter Hurley

Quoted 12 lines

Quoted 6 lines

You mean a function in 8250-dma API which does what I did just here with the wait_event() and the wake_up in the callback? That way I could move the termios_wait into the dma struct instead of keeping in the omap specific part. I am also not sure if OMAP is the only one that may hang here or the other people just didn't notice it yet.

Exactly; and we need to fix DMA wrt x_char anyway.

Going back to the dmaengine api, I think something like this might work (as a first approximation):

Quoted 8 lines

	dma_sync_wait(dma->txchan, dma->tx_cookie);
	dmaengine_pause(dma->txchan);

	/* remainder of set_termios */

	dmaengine_resume(dma->txchan);

We could require 8250 core dma to support pause/resume.

Quoted 9 lines

I would prefer the waitqueue approach.
You can't do this while holding the port lock. The lock is taken with irqs off so may not see the transfer completing.
Why do you pause the channel? It may not work without an active descriptor and a start without "resume" should work. Also you must ensure that DMA's complete callback does not start another transfer if there is something queued up (that is why I had the tx_running dance). I am not sure if a transfer that is active and then paused will not trigger the hang bug if we change the termios in between.

I'll look at/test this this weekend, ok?

Regards,
Peter Hurley

Quoted 1 line

I'll look at/test this this weekend, ok?

Sure. I'm currently re-spinning the patches so have everything in proper pieces. While at it I will take a look at x_char.

Quoted 2 lines

Regards,
Peter Hurley

On 08/06/2015 02:31 PM, Sebastian Andrzej Siewior wrote:

Hi Peter,

Quoted 4 lines

Quoted 1 line

I'll look at/test this this weekend, ok?

Sure. I'm currently re-spinning the patches so have everything in proper pieces. While at it I will take a look at x_char.

So now that I actually look at it. If I read this right, we never send the x_char if the TX-DMA never fails to do its job.

The comment above uart_send_xchar() says it is high priority.

What do you suggest, wait
until the transfer completes, send the x_char _or_ pause the transfer send that byte and then send the byte?

In both cases we have to wait until for the FIFO-empty interrupt to make sure we don't overrun that TX-FIFO.

I *think* waiting until the transfer completes would be simpler but it is not necessarily high priority.

I agree; this is what we should do first because someone might want it for backports.

Quoted 3 lines · * Peter Hurley | 2015-07-30 20:51:10 [-0400]:

I was never really a fan of the deferred set_termios(); I think it's more appropriate to wait for tx dma to complete in omap_8250_set_termios().

So you want something like this? This was only compile + boot tested (without triggering the corner case) [...] Just checking if this is what you had in mind.

drivers/tty/serial/8250/8250_omap.c +9 -13

index d9a37191a1ae..12249125a218 100644
@@ -100,9 +100,9 @@ struct omap8250_priv {
 	u8 wer;
 	u8 xon;
 	u8 xoff;
-	u8 delayed_restore;
 	u16 quot;
 
+	wait_queue_head_t termios_wait;
 	bool is_suspending;
 	int wakeirq;
 	int wakeups_enabled;

@@ -256,18 +256,6 @@ static void omap8250_update_mdr1(struct uart_8250_port *up,
 static void omap8250_restore_regs(struct uart_8250_port *up)
 {
 	struct omap8250_priv *priv = up->port.private_data;
-	struct uart_8250_dma	*dma = up->dma;
-
-	if (dma && dma->tx_running) {
-		/*
-		 * TCSANOW requests the change to occur immediately however if
-		 * we have a TX-DMA operation in progress then it has been
-		 * observed that it might stall and never complete. Therefore we
-		 * delay DMA completes to prevent this hang from happen.
-		 */
-		priv->delayed_restore = 1;
-		return;
-	}
 
 	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
 	serial_out(up, UART_EFR, UART_EFR_ECB);

@@ -309,6 +297,7 @@ static void omap8250_restore_regs(struct uart_8250_port *up)
 	up->port.ops->set_mctrl(&up->port, up->port.mctrl);
 }
 
+static void omap_8250_dma_tx_complete(void *param);
 /*
  * OMAP can use "CLK / (16 or 13) / div" for baud rate. And then we have have
  * some differences in how we want to handle flow control.

@@ -322,6 +311,7 @@ static void omap_8250_set_termios(struct uart_port *port,
 	struct omap8250_priv *priv = up->port.private_data;
 	unsigned char cval = 0;
 	unsigned int baud;
+	unsigned int complete_dma = 0;
 
 	switch (termios->c_cflag & CSIZE) {
 	case CS5:

@@ -473,6 +463,25 @@ static void omap_8250_set_termios(struct uart_port *port,
 		if (termios->c_iflag & IXANY)
 			up->mcr |= UART_MCR_XONANY;
 	}
+
+	if (up->dma && up->dma->tx_running) {
+		struct uart_8250_dma	*dma = up->dma;
+
+		/*
+		 * TCSANOW requests the change to occur immediately however if

drivers/tty/serial/8250/8250_omap.c +12 -6

+		spin_lock_irq(&up->port.lock);
+		complete_dma = 1;
+	}
 	omap8250_restore_regs(up);
 
 	spin_unlock_irq(&up->port.lock);

@@ -488,6 +497,8 @@ static void omap_8250_set_termios(struct uart_port *port,
 	/* Don't rewrite B0 */
 	if (tty_termios_baud_rate(termios))
 		tty_termios_encode_baud_rate(termios, baud, baud);
+	if (complete_dma)
+		omap_8250_dma_tx_complete(up);
 }
 
 /* same as 8250 except that we may have extra flow bits set in EFR */

@@ -869,17 +880,18 @@ static void omap_8250_dma_tx_complete(void *param)
 
 	spin_lock_irqsave(&p->port.lock, flags);
 
+	if (dma->tx_running == 2) {
+		dma->tx_running = 3;
+		wake_up(&priv->termios_wait);
+		goto out;
+	}
+
 	dma->tx_running = 0;
 
 	xmit->tail += dma->tx_size;
 	xmit->tail &= UART_XMIT_SIZE - 1;
 	p->port.icount.tx += dma->tx_size;
 
-	if (priv->delayed_restore) {
-		priv->delayed_restore = 0;
-		omap8250_restore_regs(p);
-	}
-
 	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
 		uart_write_wakeup(&p->port);
 

@@ -899,7 +911,7 @@ static void omap_8250_dma_tx_complete(void *param)
 		p->ier |= UART_IER_THRI;
 		serial_port_out(&p->port, UART_IER, p->ier);
 	}
-
+out:
 	spin_unlock_irqrestore(&p->port.lock, flags);
 }