6.6-stable review patch. If anyone has any objections, please let me know.
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From: Peter Collingbourne pcc@google.com
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@google.com Fixes: 4e26b134bd17 ("serial: 8250_dw: clock rate handling for all ACPI platforms") Cc: stable@vger.kernel.org Reviewed-by: Andy Shevchenko andriy.shevchenko@linux.intel.com Link: https://lore.kernel.org/r/20240222192635.1050502-1-pcc@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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); }