From ac048f806b24c33a331673c6b00f7482adc5b7a0 Mon Sep 17 00:00:00 2001 From: Alexey Sheplyakov Date: Tue, 11 Jan 2022 15:49:19 +0400 Subject: [PATCH 619/634] [rejected] serial: 8250_dw: verify clock rate in dw8250_set_termios Refuse to change the clock rate if clk_round_rate() returns a rate which is way too off (i.e. by more than 1/16 from the one necessary for a given baud rate). In particular this happens if the requested rate is below the minimum supported by the clock. Fixes the UART console on Baikal-M SoC. Without this patch the console gets garbled immediately after loading the driver. dw8250_set_termios tries to configure the baud rate (115200), and calls clk_round_rate to figure out the supported rate closest to 1843200 Hz (which is 115200 * 16). However the (SoC-specific) clock driver returns 4705882 Hz. This frequency is way too off, hence after setting it the console gets garbled. Signed-off-by: Alexey Sheplyakov Signed-off-by: Vadim V. Vlasov Cc: Andy Shevchenko Cc: Greg Kroah-Hartman Cc: Serge Semin --- drivers/tty/serial/8250/8250_dw.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c index 49559731b..b6d21ac44 100644 --- a/drivers/tty/serial/8250/8250_dw.c +++ b/drivers/tty/serial/8250/8250_dw.c @@ -329,14 +329,15 @@ dw8250_do_pm(struct uart_port *port, unsigned int state, unsigned int old) static void dw8250_set_termios(struct uart_port *p, struct ktermios *termios, struct ktermios *old) { - unsigned long newrate = tty_termios_baud_rate(termios) * 16; + unsigned long baud = tty_termios_baud_rate(termios); + unsigned long newrate = baud * 16; struct dw8250_data *d = to_dw8250_data(p->private_data); long rate; int ret; clk_disable_unprepare(d->clk); rate = clk_round_rate(d->clk, newrate); - if (rate > 0) { + if (rate > 0 && rate >= baud * 15 && rate <= baud * 17) { /* * Premilinary set the uartclk to the new clock rate so the * clock update event handler caused by the clk_set_rate() -- 2.33.2