This is a note to let you know that I've just added the patch titled
serial: 8250_dw: Do not reclock if already at correct rate
to the 6.6-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-do-not-reclock-if-already-at-correct-rate.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From e5d6bd25f93d6ae158bb4cd04956cb497a85b8ef Mon Sep 17 00:00:00 2001
From: Peter Collingbourne <pcc@xxxxxxxxxx>
Date: Thu, 22 Feb 2024 11:26:34 -0800
Subject: serial: 8250_dw: Do not reclock if already at correct rate
From: Peter Collingbourne <pcc@xxxxxxxxxx>
commit e5d6bd25f93d6ae158bb4cd04956cb497a85b8ef upstream.
When userspace opens the console, we call set_termios() passing a
termios with the console's configured baud rate. Currently this causes
dw8250_set_termios() to disable and then re-enable the UART clock at
the same frequency as it was originally. This can cause corruption
of any concurrent console output. Fix it by skipping the reclocking
if we are already at the correct rate.
Signed-off-by: Peter Collingbourne <pcc@xxxxxxxxxx>
Fixes: 4e26b134bd17 ("serial: 8250_dw: clock rate handling for all ACPI platforms")
Cc: stable@xxxxxxxxxxxxxxx
Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240222192635.1050502-1-pcc@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/serial/8250/8250_dw.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -357,9 +357,9 @@ static void dw8250_set_termios(struct ua
long rate;
int ret;
- clk_disable_unprepare(d->clk);
rate = clk_round_rate(d->clk, newrate);
- if (rate > 0) {
+ if (rate > 0 && p->uartclk != rate) {
+ clk_disable_unprepare(d->clk);
/*
* Note that any clock-notifer worker will block in
* serial8250_update_uartclk() until we are done.
@@ -367,8 +367,8 @@ static void dw8250_set_termios(struct ua
ret = clk_set_rate(d->clk, newrate);
if (!ret)
p->uartclk = rate;
+ clk_prepare_enable(d->clk);
}
- clk_prepare_enable(d->clk);
dw8250_do_set_termios(p, termios, old);
}
Patches currently in stable-queue which might be from pcc@xxxxxxxxxx are
queue-6.6/serial-lock-console-when-calling-into-driver-before-.patch
queue-6.6/serial-8250_dw-do-not-reclock-if-already-at-correct-rate.patch
