[PATCH for-4.19 1/2] tty/serial: atmel: Add is_half_duplex helper

[PATCH for-4.19 1/2] tty/serial: atmel: Add is_half_duplex helper

[Razvan Stefanescu]

commit f3040983132b ("tty/serial: atmel: Add is_half_duplex helper") upstream.

Use a helper function to check that a port needs to use half duplex
communication, replacing several occurrences of multi-line bit checking.

Fixes: b389f173aaa1 ("tty/serial: atmel: RS485 half duplex w/DMA: enable RX after TX is done")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Razvan Stefanescu <razvan.stefanescu@microchip.com>
Acked-by: Richard Genoud <richard.genoud@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/serial/atmel_serial.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index 8e4428725848..6b38eed7b3d0 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -225,6 +225,12 @@ static inline void atmel_uart_write_char(struct uart_port *port, u8 value)
 	__raw_writeb(value, port->membase + ATMEL_US_THR);
 }
 
+static inline int atmel_uart_is_half_duplex(struct uart_port *port)
+{
+	return (port->rs485.flags & SER_RS485_ENABLED) &&
+		!(port->rs485.flags & SER_RS485_RX_DURING_TX);
+}
+
 #ifdef CONFIG_SERIAL_ATMEL_PDC
 static bool atmel_use_pdc_rx(struct uart_port *port)
 {
@@ -481,9 +487,9 @@ static void atmel_stop_tx(struct uart_port *port)
 	/* Disable interrupts */
 	atmel_uart_writel(port, ATMEL_US_IDR, atmel_port->tx_done_mask);
 
-	if ((port->rs485.flags & SER_RS485_ENABLED) &&
-	    !(port->rs485.flags & SER_RS485_RX_DURING_TX))
+	if (atmel_uart_is_half_duplex(port))
 		atmel_start_rx(port);
+
 }
 
 /*
@@ -500,8 +506,7 @@ static void atmel_start_tx(struct uart_port *port)
 		return;
 
 	if (atmel_use_pdc_tx(port) || atmel_use_dma_tx(port))
-		if ((port->rs485.flags & SER_RS485_ENABLED) &&
-		    !(port->rs485.flags & SER_RS485_RX_DURING_TX))
+		if (atmel_uart_is_half_duplex(port))
 			atmel_stop_rx(port);
 
 	if (atmel_use_pdc_tx(port))
@@ -799,8 +804,7 @@ static void atmel_complete_tx_dma(void *arg)
 	 */
 	if (!uart_circ_empty(xmit))
 		atmel_tasklet_schedule(atmel_port, &atmel_port->tasklet_tx);
-	else if ((port->rs485.flags & SER_RS485_ENABLED) &&
-		 !(port->rs485.flags & SER_RS485_RX_DURING_TX)) {
+	else if (atmel_uart_is_half_duplex(port)) {
 		/* DMA done, stop TX, start RX for RS485 */
 		atmel_start_rx(port);
 	}
@@ -1373,8 +1377,7 @@ static void atmel_tx_pdc(struct uart_port *port)
 		atmel_uart_writel(port, ATMEL_US_IER,
 				  atmel_port->tx_done_mask);
 	} else {
-		if ((port->rs485.flags & SER_RS485_ENABLED) &&
-		    !(port->rs485.flags & SER_RS485_RX_DURING_TX)) {
+		if (atmel_uart_is_half_duplex(port)) {
 			/* DMA done, stop TX, start RX for RS485 */
 			atmel_start_rx(port);
 		}
-- 
2.19.1

[PATCH for-4.19 2/2] tty/serial: atmel: RS485 HD w/DMA: enable RX after TX is stopped

[Razvan Stefanescu]

commit 69646d7a3689 ("tty/serial: atmel: RS485 HD w/DMA: enable RX after TX is stopped") upstream.

In half-duplex operation, RX should be started after TX completes.

If DMA is used, there is a case when the DMA transfer completes but the
TX FIFO is not emptied, so the RX cannot be restarted just yet.

Use a boolean variable to store this state and rearm TX interrupt mask
to be signaled again that the transfer finished. In interrupt transmit
handler this variable is used to start RX. A warning message is generated
if RX is activated before TX fifo is cleared.

Fixes: b389f173aaa1 ("tty/serial: atmel: RS485 half duplex w/DMA: enable
RX after TX is done")
Signed-off-by: Razvan Stefanescu <razvan.stefanescu@microchip.com>
Acked-by: Richard Genoud <richard.genoud@gmail.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/serial/atmel_serial.c | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index 6b38eed7b3d0..7c49c7ce2449 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -163,6 +163,8 @@ struct atmel_uart_port {
 	unsigned int		pending_status;
 	spinlock_t		lock_suspended;
 
+	bool			hd_start_rx;	/* can start RX during half-duplex operation */
+
 #ifdef CONFIG_PM
 	struct {
 		u32		cr;
@@ -805,8 +807,13 @@ static void atmel_complete_tx_dma(void *arg)
 	if (!uart_circ_empty(xmit))
 		atmel_tasklet_schedule(atmel_port, &atmel_port->tasklet_tx);
 	else if (atmel_uart_is_half_duplex(port)) {
-		/* DMA done, stop TX, start RX for RS485 */
-		atmel_start_rx(port);
+		/*
+		 * DMA done, re-enable TXEMPTY and signal that we can stop
+		 * TX and start RX for RS485
+		 */
+		atmel_port->hd_start_rx = true;
+		atmel_uart_writel(port, ATMEL_US_IER,
+				  atmel_port->tx_done_mask);
 	}
 
 	spin_unlock_irqrestore(&port->lock, flags);
@@ -1248,9 +1255,20 @@ atmel_handle_transmit(struct uart_port *port, unsigned int pending)
 	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 
 	if (pending & atmel_port->tx_done_mask) {
-		/* Either PDC or interrupt transmission */
 		atmel_uart_writel(port, ATMEL_US_IDR,
 				  atmel_port->tx_done_mask);
+
+		/* Start RX if flag was set and FIFO is empty */
+		if (atmel_port->hd_start_rx) {
+			if (!(atmel_uart_readl(port, ATMEL_US_CSR)
+					& ATMEL_US_TXEMPTY))
+				dev_warn(port->dev, "Should start RX, but TX fifo is not empty\n");
+
+			atmel_port->hd_start_rx = false;
+			atmel_start_rx(port);
+			return;
+		}
+
 		atmel_tasklet_schedule(atmel_port, &atmel_port->tasklet_tx);
 	}
 }
-- 
2.19.1

Re: [PATCH for-4.19 2/2] tty/serial: atmel: RS485 HD w/DMA: enable RX after TX is stopped

[Greg Kroah-Hartman]

On Tue, Apr 02, 2019 at 12:52:50PM +0300, Razvan Stefanescu wrote:
> commit 69646d7a3689 ("tty/serial: atmel: RS485 HD w/DMA: enable RX after TX is stopped") upstream.
> 
> In half-duplex operation, RX should be started after TX completes.
> 
> If DMA is used, there is a case when the DMA transfer completes but the
> TX FIFO is not emptied, so the RX cannot be restarted just yet.
> 
> Use a boolean variable to store this state and rearm TX interrupt mask
> to be signaled again that the transfer finished. In interrupt transmit
> handler this variable is used to start RX. A warning message is generated
> if RX is activated before TX fifo is cleared.
> 
> Fixes: b389f173aaa1 ("tty/serial: atmel: RS485 half duplex w/DMA: enable
> RX after TX is done")
> Signed-off-by: Razvan Stefanescu <razvan.stefanescu@microchip.com>
> Acked-by: Richard Genoud <richard.genoud@gmail.com>
> Cc: stable <stable@vger.kernel.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> ---
>  drivers/tty/serial/atmel_serial.c | 24 +++++++++++++++++++++---
>  1 file changed, 21 insertions(+), 3 deletions(-)
> 

Happen to have a version of this for 4.4.y and 4.9.y?

I've queued both of these patches up now, thanks.

greg k-h

Re: [PATCH for-4.19 2/2] tty/serial: atmel: RS485 HD w/DMA: enable RX after TX is stopped

[Razvan.Stefanescu]

On 03/04/2019 17:02, Greg Kroah-Hartman wrote:
> On Tue, Apr 02, 2019 at 12:52:50PM +0300, Razvan Stefanescu wrote:
>> commit 69646d7a3689 ("tty/serial: atmel: RS485 HD w/DMA: enable RX after TX is stopped") upstream.
>>
>> In half-duplex operation, RX should be started after TX completes.
>>
>> If DMA is used, there is a case when the DMA transfer completes but the
>> TX FIFO is not emptied, so the RX cannot be restarted just yet.
>>
>> Use a boolean variable to store this state and rearm TX interrupt mask
>> to be signaled again that the transfer finished. In interrupt transmit
>> handler this variable is used to start RX. A warning message is generated
>> if RX is activated before TX fifo is cleared.
>>
>> Fixes: b389f173aaa1 ("tty/serial: atmel: RS485 half duplex w/DMA: enable
>> RX after TX is done")
>> Signed-off-by: Razvan Stefanescu <razvan.stefanescu@microchip.com>
>> Acked-by: Richard Genoud <richard.genoud@gmail.com>
>> Cc: stable <stable@vger.kernel.org>
>> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> ---
>>   drivers/tty/serial/atmel_serial.c | 24 +++++++++++++++++++++---
>>   1 file changed, 21 insertions(+), 3 deletions(-)
>>
> 
> Happen to have a version of this for 4.4.y and 4.9.y?
> 
> I've queued both of these patches up now, thanks.
> 

Thank you for picking them. I've sent the patches for 4.4.y and 4.9.y.

Best regards,
Razvan Stefanescu

Re: [PATCH for-4.19 2/2] tty/serial: atmel: RS485 HD w/DMA: enable RX after TX is stopped

[Greg KH]

On Wed, Apr 03, 2019 at 03:07:18PM +0000, Razvan.Stefanescu@microchip.com wrote:
> 
> 
> On 03/04/2019 17:02, Greg Kroah-Hartman wrote:
> > On Tue, Apr 02, 2019 at 12:52:50PM +0300, Razvan Stefanescu wrote:
> >> commit 69646d7a3689 ("tty/serial: atmel: RS485 HD w/DMA: enable RX after TX is stopped") upstream.
> >>
> >> In half-duplex operation, RX should be started after TX completes.
> >>
> >> If DMA is used, there is a case when the DMA transfer completes but the
> >> TX FIFO is not emptied, so the RX cannot be restarted just yet.
> >>
> >> Use a boolean variable to store this state and rearm TX interrupt mask
> >> to be signaled again that the transfer finished. In interrupt transmit
> >> handler this variable is used to start RX. A warning message is generated
> >> if RX is activated before TX fifo is cleared.
> >>
> >> Fixes: b389f173aaa1 ("tty/serial: atmel: RS485 half duplex w/DMA: enable
> >> RX after TX is done")
> >> Signed-off-by: Razvan Stefanescu <razvan.stefanescu@microchip.com>
> >> Acked-by: Richard Genoud <richard.genoud@gmail.com>
> >> Cc: stable <stable@vger.kernel.org>
> >> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> >> ---
> >>   drivers/tty/serial/atmel_serial.c | 24 +++++++++++++++++++++---
> >>   1 file changed, 21 insertions(+), 3 deletions(-)
> >>
> > 
> > Happen to have a version of this for 4.4.y and 4.9.y?
> > 
> > I've queued both of these patches up now, thanks.
> > 
> 
> Thank you for picking them. I've sent the patches for 4.4.y and 4.9.y.

Thanks for those, now queued up.

greg k-h