From 1abab2f81e32ed16ec6cef1dce316d1c5f5c5c30 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= <ilpo.jarvinen@linux.intel.com>
Date: Wed, 7 Sep 2022 09:24:50 +0000
Subject: [PATCH] serial: 8250_dw: Store LSR into lsr_saved_flags in
dw8250_tx_wait_empty()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
stable inclusion
from stable-v4.19.256
commit c3ca8a752a422ba1f9580f2e1d41ad650252d8ac
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5Q0SQ
CVE: NA
--------------------------------
[ 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@gmail.com>
Signed-off-by: Ilpo Jē²rvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220608095431.18376-7-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>
---
drivers/tty/serial/8250/8250_dw.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index c73d0eddd9b8..cc9d1f416db8 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -140,12 +140,15 @@ 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;
--
GitLab