Re: [PATCH v2 3/4] serial: samsung: introduce s3c24xx_serial_rx_drain_fifo() function

[Robert Baldyga]

On 09/11/2015 08:15 AM, Krzysztof Kozlowski wrote:
> On 10.09.2015 22:41, Robert Baldyga wrote:
>> This patch introduces s3c24xx_serial_rx_drain_fifo() which reads data
>> from RX FIFO and writes it to tty buffer. It also checks for special
>> conditions (such as 'break') and handles it. This function has been
>> separated from s3c24xx_serial_rx_chars_pio() as it contains code which
>> can be used also in DMA mode.
> 
> Much better, thanks! Now it is also easier to spot the difference (see
> below).
> 
>>
>> Signed-off-by: Robert Baldyga 
>> ---
>>  drivers/tty/serial/samsung.c | 23 +--
>>  1 file changed, 13 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
>> index dc4be54..1d7dd86 100644
>> --- a/drivers/tty/serial/samsung.c
>> +++ b/drivers/tty/serial/samsung.c
>> @@ -621,16 +621,12 @@ finish:
>>  return IRQ_HANDLED;
>>  }
>>  
>> -static irqreturn_t s3c24xx_serial_rx_chars_pio(void *dev_id)
>> +static void s3c24xx_serial_rx_drain_fifo(struct s3c24xx_uart_port *ourport)
>>  {
>> -struct s3c24xx_uart_port *ourport = dev_id;
>>  struct uart_port *port = >port;
>>  unsigned int ufcon, ch, flag, ufstat, uerstat;
>> -unsigned long flags;
>>  int max_count = port->fifosize;
>>  
>> -spin_lock_irqsave(>lock, flags);
>> -
>>  while (max_count-- > 0) {
>>  ufcon = rd_regl(port, S3C2410_UFCON);
>>  ufstat = rd_regl(port, S3C2410_UFSTAT);
>> @@ -654,9 +650,7 @@ static irqreturn_t s3c24xx_serial_rx_chars_pio(void 
>> *dev_id)
>>  ufcon |= S3C2410_UFCON_RESETRX;
>>  wr_regl(port, S3C2410_UFCON, ufcon);
>>  rx_enabled(port) = 1;
>> -spin_unlock_irqrestore(>lock,
>> -flags);
>> -goto out;
>> +return;
>>  }
>>  continue;
>>  }
>> @@ -702,10 +696,19 @@ static irqreturn_t s3c24xx_serial_rx_chars_pio(void 
>> *dev_id)
>>   ch, flag);
>>  }
>>  
>> -spin_unlock_irqrestore(>lock, flags);
>>  tty_flip_buffer_push(>state->port);
> 
> Here is a difference - previously this was outside of spinlock. I think
> moving it inside spin lock is okay, just the interrupts won't be
> disabled before unlock and queue_work() from tty_flip_buffer_push().
> 
> However after testing this patchset (entire) on:
> next-20150910 + my dt-for-next branch (dma for serial) + this patchset
> you can see quite complicated lockdep warning:
> 
> [3.568657] =
> [3.575079] [ INFO: possible irq lock inversion dependency detected ]
> [3.581506] 4.2.0-next-20150910-9-g65fd5a9cff54 #218 Not tainted
> [3.587838] -
> [3.594263] swapper/0/0 just changed the state of lock:
> [3.599470]  (_lock_key){..-...}, at: []
> s3c24xx_serial_tx_dma_complete+0x8c/0xfc
> [3.608237] but this lock took another, SOFTIRQ-unsafe lock in the past:
> [3.614919]  (&(>lock)->rlock){+.+...}
> [3.614919]
> [3.614919] and interrupts could create inverse lock ordering between
> them.
> [3.614919]
> [3.625076]
> [3.625076] other info that might help us debug this:
> [3.631586]  Possible interrupt unsafe locking scenario:
> [3.631586]
> [3.638356]CPU0CPU1
> [3.642870]
> [3.647382]   lock(&(>lock)->rlock);
> [3.651376]local_irq_disable();
> [3.657278]lock(_lock_key);
> [3.663267]lock(&(>lock)->rlock);
> [3.669777]   
> [3.672381] lock(_lock_key);
> 
> 
> Config: exynos, disabled MMC_CLKGATE, enabled usual testing stuff
> Board: Trats2
> 
> Didn't you notice it?
> 
> 
> Additionally the SysRq "Show backtrace of all active CPUs" on this
> linux-next (without additional patches, pure next) has significant delay
> (like 5 seconds) and a:
> [  169.221223] s3c-i2c 138d.i2c: timeout waiting for bus idle
> 
> That's weird. But as I said this occurs on pure next as well.
> 

I've noticed that commit [1] reveals the problem, but in result of git
bisect (at each step I was applying [1]) I got:

d71fc239b6915a8b750e9a447311029ff45b6580 is the first bad commit

That points to [2], which looks strange to me. However bug seems to be
unrelated to my patches, so I will send v3 soon.

[1] commit: 22374fbedb2ce03ef81323b3f7ceb3fa29344aa6
"ARM: dts: Add DMA support for serial ports in exynos4"

[2] commit: d71fc239b6915a8b750e9a447311029ff45b6580
"Merge tag 'armsoc-late' of

Re: [PATCH v2 3/4] serial: samsung: introduce s3c24xx_serial_rx_drain_fifo() function

[Robert Baldyga]

On 09/11/2015 08:15 AM, Krzysztof Kozlowski wrote:
> On 10.09.2015 22:41, Robert Baldyga wrote:
>> This patch introduces s3c24xx_serial_rx_drain_fifo() which reads data
>> from RX FIFO and writes it to tty buffer. It also checks for special
>> conditions (such as 'break') and handles it. This function has been
>> separated from s3c24xx_serial_rx_chars_pio() as it contains code which
>> can be used also in DMA mode.
> 
> Much better, thanks! Now it is also easier to spot the difference (see
> below).
> 
>>
>> Signed-off-by: Robert Baldyga 
>> ---
>>  drivers/tty/serial/samsung.c | 23 +--
>>  1 file changed, 13 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
>> index dc4be54..1d7dd86 100644
>> --- a/drivers/tty/serial/samsung.c
>> +++ b/drivers/tty/serial/samsung.c
>> @@ -621,16 +621,12 @@ finish:
>>  return IRQ_HANDLED;
>>  }
>>  
>> -static irqreturn_t s3c24xx_serial_rx_chars_pio(void *dev_id)
>> +static void s3c24xx_serial_rx_drain_fifo(struct s3c24xx_uart_port *ourport)
>>  {
>> -struct s3c24xx_uart_port *ourport = dev_id;
>>  struct uart_port *port = >port;
>>  unsigned int ufcon, ch, flag, ufstat, uerstat;
>> -unsigned long flags;
>>  int max_count = port->fifosize;
>>  
>> -spin_lock_irqsave(>lock, flags);
>> -
>>  while (max_count-- > 0) {
>>  ufcon = rd_regl(port, S3C2410_UFCON);
>>  ufstat = rd_regl(port, S3C2410_UFSTAT);
>> @@ -654,9 +650,7 @@ static irqreturn_t s3c24xx_serial_rx_chars_pio(void 
>> *dev_id)
>>  ufcon |= S3C2410_UFCON_RESETRX;
>>  wr_regl(port, S3C2410_UFCON, ufcon);
>>  rx_enabled(port) = 1;
>> -spin_unlock_irqrestore(>lock,
>> -flags);
>> -goto out;
>> +return;
>>  }
>>  continue;
>>  }
>> @@ -702,10 +696,19 @@ static irqreturn_t s3c24xx_serial_rx_chars_pio(void 
>> *dev_id)
>>   ch, flag);
>>  }
>>  
>> -spin_unlock_irqrestore(>lock, flags);
>>  tty_flip_buffer_push(>state->port);
> 
> Here is a difference - previously this was outside of spinlock. I think
> moving it inside spin lock is okay, just the interrupts won't be
> disabled before unlock and queue_work() from tty_flip_buffer_push().
> 
> However after testing this patchset (entire) on:
> next-20150910 + my dt-for-next branch (dma for serial) + this patchset
> you can see quite complicated lockdep warning:
> 
> [3.568657] =
> [3.575079] [ INFO: possible irq lock inversion dependency detected ]
> [3.581506] 4.2.0-next-20150910-9-g65fd5a9cff54 #218 Not tainted
> [3.587838] -
> [3.594263] swapper/0/0 just changed the state of lock:
> [3.599470]  (_lock_key){..-...}, at: []
> s3c24xx_serial_tx_dma_complete+0x8c/0xfc
> [3.608237] but this lock took another, SOFTIRQ-unsafe lock in the past:
> [3.614919]  (&(>lock)->rlock){+.+...}
> [3.614919]
> [3.614919] and interrupts could create inverse lock ordering between
> them.
> [3.614919]
> [3.625076]
> [3.625076] other info that might help us debug this:
> [3.631586]  Possible interrupt unsafe locking scenario:
> [3.631586]
> [3.638356]CPU0CPU1
> [3.642870]
> [3.647382]   lock(&(>lock)->rlock);
> [3.651376]local_irq_disable();
> [3.657278]lock(_lock_key);
> [3.663267]lock(&(>lock)->rlock);
> [3.669777]   
> [3.672381] lock(_lock_key);
> 
> 
> Config: exynos, disabled MMC_CLKGATE, enabled usual testing stuff
> Board: Trats2
> 
> Didn't you notice it?
> 
> 
> Additionally the SysRq "Show backtrace of all active CPUs" on this
> linux-next (without additional patches, pure next) has significant delay
> (like 5 seconds) and a:
> [  169.221223] s3c-i2c 138d.i2c: timeout waiting for bus idle
> 
> That's weird. But as I said this occurs on pure next as well.
> 

I've noticed that commit [1] reveals the problem, but in result of git
bisect (at each step I was applying [1]) I got:

d71fc239b6915a8b750e9a447311029ff45b6580 is the first bad commit

That points to [2], which looks strange to me. However bug seems to be
unrelated to my patches, so I will send v3 soon.

[1] commit: 22374fbedb2ce03ef81323b3f7ceb3fa29344aa6
"ARM: dts: Add DMA support for serial ports in exynos4"

[2] commit: d71fc239b6915a8b750e9a447311029ff45b6580
"Merge tag 'armsoc-late' of

Re: [PATCH v2 3/4] serial: samsung: introduce s3c24xx_serial_rx_drain_fifo() function

[Krzysztof Kozlowski]

On 10.09.2015 22:41, Robert Baldyga wrote:
> This patch introduces s3c24xx_serial_rx_drain_fifo() which reads data
> from RX FIFO and writes it to tty buffer. It also checks for special
> conditions (such as 'break') and handles it. This function has been
> separated from s3c24xx_serial_rx_chars_pio() as it contains code which
> can be used also in DMA mode.

Much better, thanks! Now it is also easier to spot the difference (see
below).

> 
> Signed-off-by: Robert Baldyga 
> ---
>  drivers/tty/serial/samsung.c | 23 +--
>  1 file changed, 13 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
> index dc4be54..1d7dd86 100644
> --- a/drivers/tty/serial/samsung.c
> +++ b/drivers/tty/serial/samsung.c
> @@ -621,16 +621,12 @@ finish:
>   return IRQ_HANDLED;
>  }
>  
> -static irqreturn_t s3c24xx_serial_rx_chars_pio(void *dev_id)
> +static void s3c24xx_serial_rx_drain_fifo(struct s3c24xx_uart_port *ourport)
>  {
> - struct s3c24xx_uart_port *ourport = dev_id;
>   struct uart_port *port = >port;
>   unsigned int ufcon, ch, flag, ufstat, uerstat;
> - unsigned long flags;
>   int max_count = port->fifosize;
>  
> - spin_lock_irqsave(>lock, flags);
> -
>   while (max_count-- > 0) {
>   ufcon = rd_regl(port, S3C2410_UFCON);
>   ufstat = rd_regl(port, S3C2410_UFSTAT);
> @@ -654,9 +650,7 @@ static irqreturn_t s3c24xx_serial_rx_chars_pio(void 
> *dev_id)
>   ufcon |= S3C2410_UFCON_RESETRX;
>   wr_regl(port, S3C2410_UFCON, ufcon);
>   rx_enabled(port) = 1;
> - spin_unlock_irqrestore(>lock,
> - flags);
> - goto out;
> + return;
>   }
>   continue;
>   }
> @@ -702,10 +696,19 @@ static irqreturn_t s3c24xx_serial_rx_chars_pio(void 
> *dev_id)
>ch, flag);
>   }
>  
> - spin_unlock_irqrestore(>lock, flags);
>   tty_flip_buffer_push(>state->port);

Here is a difference - previously this was outside of spinlock. I think
moving it inside spin lock is okay, just the interrupts won't be
disabled before unlock and queue_work() from tty_flip_buffer_push().

However after testing this patchset (entire) on:
next-20150910 + my dt-for-next branch (dma for serial) + this patchset
you can see quite complicated lockdep warning:

[3.568657] =
[3.575079] [ INFO: possible irq lock inversion dependency detected ]
[3.581506] 4.2.0-next-20150910-9-g65fd5a9cff54 #218 Not tainted
[3.587838] -
[3.594263] swapper/0/0 just changed the state of lock:
[3.599470]  (_lock_key){..-...}, at: []
s3c24xx_serial_tx_dma_complete+0x8c/0xfc
[3.608237] but this lock took another, SOFTIRQ-unsafe lock in the past:
[3.614919]  (&(>lock)->rlock){+.+...}
[3.614919]
[3.614919] and interrupts could create inverse lock ordering between
them.
[3.614919]
[3.625076]
[3.625076] other info that might help us debug this:
[3.631586]  Possible interrupt unsafe locking scenario:
[3.631586]
[3.638356]CPU0CPU1
[3.642870]
[3.647382]   lock(&(>lock)->rlock);
[3.651376]local_irq_disable();
[3.657278]lock(_lock_key);
[3.663267]lock(&(>lock)->rlock);
[3.669777]   
[3.672381] lock(_lock_key);


Config: exynos, disabled MMC_CLKGATE, enabled usual testing stuff
Board: Trats2

Didn't you notice it?


Additionally the SysRq "Show backtrace of all active CPUs" on this
linux-next (without additional patches, pure next) has significant delay
(like 5 seconds) and a:
[  169.221223] s3c-i2c 138d.i2c: timeout waiting for bus idle

That's weird. But as I said this occurs on pure next as well.

Dmesgs and config attached.

Best regards,
Krzysztof


> +}
> +
> +static irqreturn_t s3c24xx_serial_rx_chars_pio(void *dev_id)
> +{
> + struct s3c24xx_uart_port *ourport = dev_id;
> + struct uart_port *port = >port;
> + unsigned long flags;
> +
> + spin_lock_irqsave(>lock, flags);
> + s3c24xx_serial_rx_drain_fifo(ourport);
> + spin_unlock_irqrestore(>lock, flags);
>  
> -out:
>   return IRQ_HANDLED;
>  }
>  
> 

-sh-4.1# [  164.160601] sysrq: SysRq : Show backtrace of all active CPUs
[  164.164815] Sending NMI to all CPUs:
[  169.221223] s3c-i2c 138d.i2c: timeout waiting for bus idle
[  174.175570] NMI backtrace for cpu 1
[  174.177607] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.2.0-next-20150910 

Re: [PATCH v2 3/4] serial: samsung: introduce s3c24xx_serial_rx_drain_fifo() function

[Krzysztof Kozlowski]

On 10.09.2015 22:41, Robert Baldyga wrote:
> This patch introduces s3c24xx_serial_rx_drain_fifo() which reads data
> from RX FIFO and writes it to tty buffer. It also checks for special
> conditions (such as 'break') and handles it. This function has been
> separated from s3c24xx_serial_rx_chars_pio() as it contains code which
> can be used also in DMA mode.

Much better, thanks! Now it is also easier to spot the difference (see
below).

> 
> Signed-off-by: Robert Baldyga 
> ---
>  drivers/tty/serial/samsung.c | 23 +--
>  1 file changed, 13 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
> index dc4be54..1d7dd86 100644
> --- a/drivers/tty/serial/samsung.c
> +++ b/drivers/tty/serial/samsung.c
> @@ -621,16 +621,12 @@ finish:
>   return IRQ_HANDLED;
>  }
>  
> -static irqreturn_t s3c24xx_serial_rx_chars_pio(void *dev_id)
> +static void s3c24xx_serial_rx_drain_fifo(struct s3c24xx_uart_port *ourport)
>  {
> - struct s3c24xx_uart_port *ourport = dev_id;
>   struct uart_port *port = >port;
>   unsigned int ufcon, ch, flag, ufstat, uerstat;
> - unsigned long flags;
>   int max_count = port->fifosize;
>  
> - spin_lock_irqsave(>lock, flags);
> -
>   while (max_count-- > 0) {
>   ufcon = rd_regl(port, S3C2410_UFCON);
>   ufstat = rd_regl(port, S3C2410_UFSTAT);
> @@ -654,9 +650,7 @@ static irqreturn_t s3c24xx_serial_rx_chars_pio(void 
> *dev_id)
>   ufcon |= S3C2410_UFCON_RESETRX;
>   wr_regl(port, S3C2410_UFCON, ufcon);
>   rx_enabled(port) = 1;
> - spin_unlock_irqrestore(>lock,
> - flags);
> - goto out;
> + return;
>   }
>   continue;
>   }
> @@ -702,10 +696,19 @@ static irqreturn_t s3c24xx_serial_rx_chars_pio(void 
> *dev_id)
>ch, flag);
>   }
>  
> - spin_unlock_irqrestore(>lock, flags);
>   tty_flip_buffer_push(>state->port);

Here is a difference - previously this was outside of spinlock. I think
moving it inside spin lock is okay, just the interrupts won't be
disabled before unlock and queue_work() from tty_flip_buffer_push().

However after testing this patchset (entire) on:
next-20150910 + my dt-for-next branch (dma for serial) + this patchset
you can see quite complicated lockdep warning:

[3.568657] =
[3.575079] [ INFO: possible irq lock inversion dependency detected ]
[3.581506] 4.2.0-next-20150910-9-g65fd5a9cff54 #218 Not tainted
[3.587838] -
[3.594263] swapper/0/0 just changed the state of lock:
[3.599470]  (_lock_key){..-...}, at: []
s3c24xx_serial_tx_dma_complete+0x8c/0xfc
[3.608237] but this lock took another, SOFTIRQ-unsafe lock in the past:
[3.614919]  (&(>lock)->rlock){+.+...}
[3.614919]
[3.614919] and interrupts could create inverse lock ordering between
them.
[3.614919]
[3.625076]
[3.625076] other info that might help us debug this:
[3.631586]  Possible interrupt unsafe locking scenario:
[3.631586]
[3.638356]CPU0CPU1
[3.642870]
[3.647382]   lock(&(>lock)->rlock);
[3.651376]local_irq_disable();
[3.657278]lock(_lock_key);
[3.663267]lock(&(>lock)->rlock);
[3.669777]   
[3.672381] lock(_lock_key);


Config: exynos, disabled MMC_CLKGATE, enabled usual testing stuff
Board: Trats2

Didn't you notice it?


Additionally the SysRq "Show backtrace of all active CPUs" on this
linux-next (without additional patches, pure next) has significant delay
(like 5 seconds) and a:
[  169.221223] s3c-i2c 138d.i2c: timeout waiting for bus idle

That's weird. But as I said this occurs on pure next as well.

Dmesgs and config attached.

Best regards,
Krzysztof


> +}
> +
> +static irqreturn_t s3c24xx_serial_rx_chars_pio(void *dev_id)
> +{
> + struct s3c24xx_uart_port *ourport = dev_id;
> + struct uart_port *port = >port;
> + unsigned long flags;
> +
> + spin_lock_irqsave(>lock, flags);
> + s3c24xx_serial_rx_drain_fifo(ourport);
> + spin_unlock_irqrestore(>lock, flags);
>  
> -out:
>   return IRQ_HANDLED;
>  }
>  
> 

-sh-4.1# [  164.160601] sysrq: SysRq : Show backtrace of all active CPUs
[  164.164815] Sending NMI to all CPUs:
[  169.221223] s3c-i2c 138d.i2c: timeout waiting for bus idle
[  174.175570] NMI backtrace for cpu 1
[  174.177607] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 

[PATCH v2 3/4] serial: samsung: introduce s3c24xx_serial_rx_drain_fifo() function

[Robert Baldyga]

This patch introduces s3c24xx_serial_rx_drain_fifo() which reads data
from RX FIFO and writes it to tty buffer. It also checks for special
conditions (such as 'break') and handles it. This function has been
separated from s3c24xx_serial_rx_chars_pio() as it contains code which
can be used also in DMA mode.

Signed-off-by: Robert Baldyga 
---
 drivers/tty/serial/samsung.c | 23 +--
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
index dc4be54..1d7dd86 100644
--- a/drivers/tty/serial/samsung.c
+++ b/drivers/tty/serial/samsung.c
@@ -621,16 +621,12 @@ finish:
return IRQ_HANDLED;
 }
 
-static irqreturn_t s3c24xx_serial_rx_chars_pio(void *dev_id)
+static void s3c24xx_serial_rx_drain_fifo(struct s3c24xx_uart_port *ourport)
 {
-   struct s3c24xx_uart_port *ourport = dev_id;
struct uart_port *port = >port;
unsigned int ufcon, ch, flag, ufstat, uerstat;
-   unsigned long flags;
int max_count = port->fifosize;
 
-   spin_lock_irqsave(>lock, flags);
-
while (max_count-- > 0) {
ufcon = rd_regl(port, S3C2410_UFCON);
ufstat = rd_regl(port, S3C2410_UFSTAT);
@@ -654,9 +650,7 @@ static irqreturn_t s3c24xx_serial_rx_chars_pio(void *dev_id)
ufcon |= S3C2410_UFCON_RESETRX;
wr_regl(port, S3C2410_UFCON, ufcon);
rx_enabled(port) = 1;
-   spin_unlock_irqrestore(>lock,
-   flags);
-   goto out;
+   return;
}
continue;
}
@@ -702,10 +696,19 @@ static irqreturn_t s3c24xx_serial_rx_chars_pio(void 
*dev_id)
 ch, flag);
}
 
-   spin_unlock_irqrestore(>lock, flags);
tty_flip_buffer_push(>state->port);
+}
+
+static irqreturn_t s3c24xx_serial_rx_chars_pio(void *dev_id)
+{
+   struct s3c24xx_uart_port *ourport = dev_id;
+   struct uart_port *port = >port;
+   unsigned long flags;
+
+   spin_lock_irqsave(>lock, flags);
+   s3c24xx_serial_rx_drain_fifo(ourport);
+   spin_unlock_irqrestore(>lock, flags);
 
-out:
return IRQ_HANDLED;
 }
 
-- 
1.9.1

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[PATCH v2 3/4] serial: samsung: introduce s3c24xx_serial_rx_drain_fifo() function

[Robert Baldyga]

This patch introduces s3c24xx_serial_rx_drain_fifo() which reads data
from RX FIFO and writes it to tty buffer. It also checks for special
conditions (such as 'break') and handles it. This function has been
separated from s3c24xx_serial_rx_chars_pio() as it contains code which
can be used also in DMA mode.

Signed-off-by: Robert Baldyga 
---
 drivers/tty/serial/samsung.c | 23 +--
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
index dc4be54..1d7dd86 100644
--- a/drivers/tty/serial/samsung.c
+++ b/drivers/tty/serial/samsung.c
@@ -621,16 +621,12 @@ finish:
return IRQ_HANDLED;
 }
 
-static irqreturn_t s3c24xx_serial_rx_chars_pio(void *dev_id)
+static void s3c24xx_serial_rx_drain_fifo(struct s3c24xx_uart_port *ourport)
 {
-   struct s3c24xx_uart_port *ourport = dev_id;
struct uart_port *port = >port;
unsigned int ufcon, ch, flag, ufstat, uerstat;
-   unsigned long flags;
int max_count = port->fifosize;
 
-   spin_lock_irqsave(>lock, flags);
-
while (max_count-- > 0) {
ufcon = rd_regl(port, S3C2410_UFCON);
ufstat = rd_regl(port, S3C2410_UFSTAT);
@@ -654,9 +650,7 @@ static irqreturn_t s3c24xx_serial_rx_chars_pio(void *dev_id)
ufcon |= S3C2410_UFCON_RESETRX;
wr_regl(port, S3C2410_UFCON, ufcon);
rx_enabled(port) = 1;
-   spin_unlock_irqrestore(>lock,
-   flags);
-   goto out;
+   return;
}
continue;
}
@@ -702,10 +696,19 @@ static irqreturn_t s3c24xx_serial_rx_chars_pio(void 
*dev_id)
 ch, flag);
}
 
-   spin_unlock_irqrestore(>lock, flags);
tty_flip_buffer_push(>state->port);
+}
+
+static irqreturn_t s3c24xx_serial_rx_chars_pio(void *dev_id)
+{
+   struct s3c24xx_uart_port *ourport = dev_id;
+   struct uart_port *port = >port;
+   unsigned long flags;
+
+   spin_lock_irqsave(>lock, flags);
+   s3c24xx_serial_rx_drain_fifo(ourport);
+   spin_unlock_irqrestore(>lock, flags);
 
-out:
return IRQ_HANDLED;
 }
 
-- 
1.9.1

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