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authorPali Rohár <pali@kernel.org>2020-12-23 22:19:31 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2020-12-28 18:17:34 +0300
commit54ca955b5a4024e2ce0f206b03adb7109bc4da26 (patch)
tree04e7308b7888995b2d5ad3b8d30de526b75d01fe /drivers/tty/serial/mvebu-uart.c
parent5c8fe583cce542aa0b84adc939ce85293de36e5e (diff)
downloadlinux-54ca955b5a4024e2ce0f206b03adb7109bc4da26.tar.xz
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>
Diffstat (limited to 'drivers/tty/serial/mvebu-uart.c')
-rw-r--r--drivers/tty/serial/mvebu-uart.c10
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));