diff options
| author | Pali Rohár <pali@kernel.org> | 2020-12-23 20:19:31 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-12-28 16:17:34 +0100 |
| commit | 54ca955b5a4024e2ce0f206b03adb7109bc4da26 (patch) | |
| tree | 04e7308b7888995b2d5ad3b8d30de526b75d01fe | |
| parent | 5c8fe583cce542aa0b84adc939ce85293de36e5e (diff) | |
| download | linux-54ca955b5a4024e2ce0f206b03adb7109bc4da26.tar.bz2 | |
serial: mvebu-uart: fix tx lost characters at power off
Commit c685af1108d7 ("serial: mvebu-uart: fix tx lost characters") fixed tx
lost characters at low baud rates but started causing tx lost characters
when kernel is going to power off or reboot.
TX_EMP tells us when transmit queue is empty therefore all characters were
transmitted. TX_RDY tells us when CPU can send a new character.
Therefore we need to use different check prior transmitting new character
and different check after all characters were sent.
This patch splits polling code into two functions: wait_for_xmitr() which
waits for TX_RDY and wait_for_xmite() which waits for TX_EMP.
When rebooting A3720 platform without this patch on UART is print only:
[ 42.699�
And with this patch on UART is full output:
[ 39.530216] reboot: Restarting system
Fixes: c685af1108d7 ("serial: mvebu-uart: fix tx lost characters")
Signed-off-by: Pali Rohár <pali@kernel.org>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20201223191931.18343-1-pali@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/tty/serial/mvebu-uart.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/drivers/tty/serial/mvebu-uart.c b/drivers/tty/serial/mvebu-uart.c index 118b29912289..e0c00a1b0763 100644 --- a/drivers/tty/serial/mvebu-uart.c +++ b/drivers/tty/serial/mvebu-uart.c @@ -648,6 +648,14 @@ static void wait_for_xmitr(struct uart_port *port) (val & STAT_TX_RDY(port)), 1, 10000); } +static void wait_for_xmite(struct uart_port *port) +{ + u32 val; + + readl_poll_timeout_atomic(port->membase + UART_STAT, val, + (val & STAT_TX_EMP), 1, 10000); +} + static void mvebu_uart_console_putchar(struct uart_port *port, int ch) { wait_for_xmitr(port); @@ -675,7 +683,7 @@ static void mvebu_uart_console_write(struct console *co, const char *s, uart_console_write(port, s, count, mvebu_uart_console_putchar); - wait_for_xmitr(port); + wait_for_xmite(port); if (ier) writel(ier, port->membase + UART_CTRL(port)); |