serial: mvebu-uart: fix tx lost characters

-----Original Message-----
From: [email protected] <[email protected]>
Sent: March 20, 2018 5:32 AM
To: Gabriel Matni <[email protected]>
Cc: Miquel Raynal <[email protected]>; linux- [email protected]; [email protected]; [email protected]; Grégory Clement <[email protected]>; Thomas Petazzoni <[email protected]>
Subject: Re: [PATCH] serial: mvebu-uart: fix tx lost characters

Quoted 4 lines · Gabriel Matni

From: Gabriel Matni <[email protected]>

Fixes missing characters on kernel console at low baud rates (i.e.9600). The driver should poll TX_RDY or TX_FIFO_EMP instead of TX_EMP to

ensure

Quoted 8 lines

that the transmitter holding register (THR) is ready to receive a new byte.

TX_EMP tells us when it is possible to send a break sequence via SND_BRK_SEQ. While this also indicates that both the THR and the TSR are empty, it does not guarantee that a new byte can be written just yet.

Fixes 30530791a7a0 ("serial: mvebu-uart: initial support for Armada-3700

serial port")

Can all be on one line.

And should this go to the stable trees?

Quoted 3 lines

Reviewed-by Miquel Raynal <[email protected]>

Acked-by Gregory CLEMENT <[email protected]>

Signed-off-by Gabriel Matni <[email protected]>

Trailing whitespace?

Quoted 4 lines

---
 drivers/tty/serial/mvebu-uart.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

What version of this patch is this? How do I know which to accept?

Please properly version your patch, and include the changes below the --- line like the documentation says to do.

thanks,

greg k-h

From: Gabriel Matni <[email protected]>

Fixes missing characters on kernel console at low baud rates (i.e.9600). The driver should poll TX_RDY or TX_FIFO_EMP instead of TX_EMP to ensure that the transmitter holding register (THR) is ready to receive a new byte.

TX_EMP tells us when it is possible to send a break sequence via SND_BRK_SEQ. While this also indicates that both the THR and the TSR are empty, it does not guarantee that a new byte can be written just yet.

Fixes 30530791a7a0 ("serial: mvebu-uart: initial support for Armada-3700 serial port")

Reviewed-by Miquel Raynal <[email protected]>

Acked-by Gregory CLEMENT <[email protected]>

Signed-off-by Gabriel Matni <[email protected]>

---
Changes since v2:
- use one line for the "Fixes" entry
- removed trailing space between Signed-off-by entry and ---
- start using versioning, previous fixes in v1

Changes since v1:
- patch was corrupt, could not be applied
- fixed line indent

---
 drivers/tty/serial/mvebu-uart.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

drivers/tty/serial/mvebu-uart.c +1 -1

index a100e98259d7..f0df0640208e 100644
@@ -618,7 +618,7 @@ static void wait_for_xmitr(struct uart_port *port)
 	u32 val;
 
 	readl_poll_timeout_atomic(port->membase + UART_STAT, val,
-				  (val & STAT_TX_EMP), 1, 10000);
+				  (val & STAT_TX_RDY(port)), 1, 10000);
 }
 
 static void mvebu_uart_console_putchar(struct uart_port *port, int ch)

Signature · 1 line

2.7.4

Quoted 9 lines

-----Original Message-----
From: gregkh at linuxfoundation.org <[email protected]>
Sent: March 20, 2018 5:32 AM
To: Gabriel Matni <[email protected]>
Cc: Miquel Raynal <[email protected]>; linux-
serial at vger.kernel.org; linux-arm-kernel at lists.infradead.org; stable at vger.kernel.org; Gr?gory Clement <[email protected]>; Thomas Petazzoni <[email protected]>
Subject: Re: [PATCH] serial: mvebu-uart: fix tx lost characters