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serial: mvebu-uart: fix tx lost characters 

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: 30530791a7 ("serial: mvebu-uart: initial support for Armada-3700 serial port")
Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Gregory CLEMENT <gregory.clement@bootlin.com>
Signed-off-by: Gabriel Matni <gabriel.matni@exfo.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Gabriel Matni 2018-03-22 19:15:12 +00:00 committed by Greg Kroah-Hartman
parent 7693b331d0
commit c685af1108
1 changed files with 1 additions and 1 deletions
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2
drivers/tty/serial/mvebu-uart.c
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@ -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)