tty: serial: meson: Use DIV_ROUND_CLOSEST to calculate baud rates

Due to chip process differences, chip designers recommend using baud
rates as close to and larger as possible in order to reduce clock
errors.

Signed-off-by: Yu Tu <yu.tu@amlogic.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://lore.kernel.org/r/20220407081355.13602-2-yu.tu@amlogic.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c
index 2bf1c57e0981eac868eb717ed5668817ec375a2f..8e59624935af143e6ad7a59cc5382552eb9e7949 100644 (file)
--- a/drivers/tty/serial/meson_uart.c
+++ b/drivers/tty/serial/meson_uart.c
@@ -299,10 +299,10 @@ static void meson_uart_change_speed(struct uart_port *port, unsigned long baud)
                cpu_relax();
 
        if (port->uartclk == 24000000) {
-               val = ((port->uartclk / 3) / baud) - 1;
+               val = DIV_ROUND_CLOSEST(port->uartclk / 3, baud) - 1;
                val |= AML_UART_BAUD_XTAL;
        } else {
-               val = ((port->uartclk * 10 / (baud * 4) + 5) / 10) - 1;
+               val =  DIV_ROUND_CLOSEST(port->uartclk / 4, baud) - 1;
        }
        val |= AML_UART_BAUD_USE;
        writel(val, port->membase + AML_UART_REG5);