This is a note to let you know that I've just added the patch titled
serial: 8250_dw: Store LSR into lsr_saved_flags in dw8250_tx_wait_empty()
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
serial-8250_dw-store-lsr-into-lsr_saved_flags-in-dw8.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 1d4188cce8ba42e2c777dcdfff62acaaf60bf28f
Author: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
Date: Wed Jun 8 12:54:31 2022 +0300
serial: 8250_dw: Store LSR into lsr_saved_flags in dw8250_tx_wait_empty()
[ Upstream commit af14f3007e2dca0d112f10f6717ba43093f74e81 ]
Make sure LSR flags are preserved in dw8250_tx_wait_empty(). This
function is called from a low-level out function and therefore cannot
call serial_lsr_in() as it would lead to infinite recursion.
It is borderline if the flags need to be saved here at all since this
code relates to writing LCR register which usually implies no important
characters should be arriving.
Fixes: 914eaf935ec7 ("serial: 8250_dw: Allow TX FIFO to drain before writing to UART_LCR")
Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20220608095431.18376-7-ilpo.jarvinen@xxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index 381c5117aec1..2d5a039229ac 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -110,12 +110,15 @@ static void dw8250_check_lcr(struct uart_port *p, int value)
/* Returns once the transmitter is empty or we run out of retries */
static void dw8250_tx_wait_empty(struct uart_port *p)
{
+ struct uart_8250_port *up = up_to_u8250p(p);
unsigned int tries = 20000;
unsigned int delay_threshold = tries - 1000;
unsigned int lsr;
while (tries--) {
lsr = readb (p->membase + (UART_LSR << p->regshift));
+ up->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS;
+
if (lsr & UART_LSR_TEMT)
break;
