From: Gabriel Matni <gabriel.matni@xxxxxxxx>
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 <miquel.raynal@xxxxxxxxxxx>
Acked-by: Gregory CLEMENT <gregory.clement@xxxxxxxxxxx>
Signed-off-by: Gabriel Matni <gabriel.matni@xxxxxxxx>
---
drivers/tty/serial/mvebu-uart.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/tty/serial/mvebu-uart.c b/drivers/tty/serial/mvebu-uart.c
index a100e98259d7..f0df0640208e 100644
--- a/drivers/tty/serial/mvebu-uart.c
+++ b/drivers/tty/serial/mvebu-uart.c
@@ -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)
--
2.7.4
> -----Original Message-----
> From: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
> Sent: March 15, 2018 4:22 PM
> To: Gabriel Matni <gabriel.matni@xxxxxxxx>
> Cc: gregkh@xxxxxxxxxxxxxxxxxxx; linux-serial@xxxxxxxxxxxxxxx; linux-arm-
> kernel@xxxxxxxxxxxxxxxxxxx; stable@xxxxxxxxxxxxxxx; Grégory Clement
> <gregory.clement@xxxxxxxxxxx>; Thomas Petazzoni
> <thomas.petazzoni@xxxxxxxxxxx>
> Subject: Re: [PATCH] serial: mvebu-uart: fix tx lost characters
>
> Hi Gabriel,
>
> On Thu, 15 Mar 2018 18:55:25 +0000, Gabriel Matni
> <gabriel.matni@xxxxxxxx> wrote:
>
> > From: Gabriel Matni <gabriel.matni@xxxxxxxx>
> >
> > 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 <miquel.raynal@xxxxxxxxxxx>
> > Acked-by: Gregory CLEMENT <gregory.clement@xxxxxxxxxxx>
> > Signed-off-by: Gabriel Matni <gabriel.matni@xxxxxxxx>
> >
> > ---
> > drivers/tty/serial/mvebu-uart.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/tty/serial/mvebu-uart.c b/drivers/tty/serial/mvebu-
> uart.c
> > index a100e98259d7..400e1bc558b2 100644
> > --- a/drivers/tty/serial/mvebu-uart.c
> > +++ b/drivers/tty/serial/mvebu-uart.c
> > @@ -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);
>
> I think this line should be indented like the one you replaced.
>
> Thanks,
> Miquèl
>
> --
> Miquel Raynal, Bootlin (formerly Free Electrons)
> Embedded Linux and Kernel engineering
> https://bootlin.com