Switch in uart_get_baud_rate() function is missing case for UPF_SPD_CUST flag. It is not obvious why it is missing here, so add comments explaining how deprecated UPF_SPD_CUST flag is handled and how drivers should call uart_get_baud_rate() and uart_get_divisor() functions. Signed-off-by: Pali Rohár <pali@xxxxxxxxxx> --- drivers/tty/serial/serial_core.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index 1e738f265eea..d8fc2616d62b 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -364,7 +364,17 @@ EXPORT_SYMBOL(uart_update_timeout); * * Decode the termios structure into a numeric baud rate, * taking account of the magic 38400 baud rate (with spd_* - * flags), and mapping the %B0 rate to 9600 baud. + * flags, except cust), and mapping the %B0 rate to 9600 baud. + * + * UPF_SPD_CUST flag is not handled in this function as it applies + * to the custom divisor. When UPF_SPD_CUST flag is active and in + * use then this function returns value 38400 and not the correct + * baud rate. + * + * Drivers should call uart_get_divisor() function with baud rate + * returned from this function to calculate clock divisor. Function + * uart_get_divisor() then handles UPF_SPD_CUST flag with magic + * baud rate value 38400 and returns the correct custom divisor. * * If the new baud rate is invalid, try the old termios setting. * If it's still invalid, we try 9600 baud. @@ -396,6 +406,7 @@ uart_get_baud_rate(struct uart_port *port, struct ktermios *termios, case UPF_SPD_WARP: altbaud = 460800; break; + /* Flag UPF_SPD_CUST is not handed here, see description why. */ default: altbaud = 38400; break; @@ -462,6 +473,8 @@ EXPORT_SYMBOL(uart_get_baud_rate); * @baud: desired baud rate * * Calculate the uart clock divisor for the port. + * + * Handles also special case when UPF_SPD_CUST flag is in use. */ unsigned int uart_get_divisor(struct uart_port *port, unsigned int baud) -- 2.20.1
