From: Pali Rohár pali@kernel.org
[ Upstream commit deeaf963569a0d9d1b08babb771f61bb501a5704 ]
For default (x16) scheme which is currently used by mvebu-uart.c driver, maximal divisor of UART base clock is 1023*16. Therefore there is limit for minimal supported baudrate. This change calculate it correctly and prevents setting invalid divisor 0 into hardware registers.
Signed-off-by: Pali Rohár pali@kernel.org Fixes: 68a0db1d7da2 ("serial: mvebu-uart: add function to change baudrate") Link: https://lore.kernel.org/r/20210624224909.6350-4-pali@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/tty/serial/mvebu-uart.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/drivers/tty/serial/mvebu-uart.c b/drivers/tty/serial/mvebu-uart.c index 9638ae6aae79..1e26220c7852 100644 --- a/drivers/tty/serial/mvebu-uart.c +++ b/drivers/tty/serial/mvebu-uart.c @@ -481,7 +481,7 @@ static void mvebu_uart_set_termios(struct uart_port *port, struct ktermios *old) { unsigned long flags; - unsigned int baud; + unsigned int baud, min_baud, max_baud;
spin_lock_irqsave(&port->lock, flags);
@@ -500,16 +500,21 @@ static void mvebu_uart_set_termios(struct uart_port *port, port->ignore_status_mask |= STAT_RX_RDY(port) | STAT_BRK_ERR;
/* + * Maximal divisor is 1023 * 16 when using default (x16) scheme. * Maximum achievable frequency with simple baudrate divisor is 230400. * Since the error per bit frame would be of more than 15%, achieving * higher frequencies would require to implement the fractional divisor * feature. */ - baud = uart_get_baud_rate(port, termios, old, 0, 230400); + min_baud = DIV_ROUND_UP(port->uartclk, 1023 * 16); + max_baud = 230400; + + baud = uart_get_baud_rate(port, termios, old, min_baud, max_baud); if (mvebu_uart_baud_rate_set(port, baud)) { /* No clock available, baudrate cannot be changed */ if (old) - baud = uart_get_baud_rate(port, old, NULL, 0, 230400); + baud = uart_get_baud_rate(port, old, NULL, + min_baud, max_baud); } else { tty_termios_encode_baud_rate(termios, baud, baud); uart_update_timeout(port, termios->c_cflag, baud);