On Sat, Sep 24, 2022 at 12:27:15PM +0200, Pali Rohár wrote:
> If setting new baud rate fails, some other drivers leave the device at
> previous baud rate, and ftdi_sio resets to 9600 Baud.
>
> Change this behavior to not reset baud rate to 9600.
>
> Signed-off-by: Pali Rohár <pali@xxxxxxxxxx>
> Tested-by: Marek Behún <kabel@xxxxxxxxxx>
> Signed-off-by: Marek Behún <kabel@xxxxxxxxxx>
> ---
> drivers/usb/serial/ftdi_sio.c | 47 ++++++++++++++++++++++++++---------
> 1 file changed, 35 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
> index fe8a7c5fa0e9..1ab6bf48516f 100644
> --- a/drivers/usb/serial/ftdi_sio.c
> +++ b/drivers/usb/serial/ftdi_sio.c
> @@ -1315,7 +1315,7 @@ static int update_mctrl(struct usb_serial_port *port, unsigned int set,
>
>
> static u32 get_ftdi_divisor(struct tty_struct *tty,
> - struct usb_serial_port *port)
> + struct usb_serial_port *port, speed_t old_baud)
> {
> struct ftdi_private *priv = usb_get_serial_port_data(port);
> struct device *dev = &port->dev;
> @@ -1338,6 +1338,8 @@ static u32 get_ftdi_divisor(struct tty_struct *tty,
> __func__, priv->custom_divisor, baud);
> }
>
> + if (!baud)
> + baud = old_baud;
> if (!baud)
> baud = 9600;
While not apparent from just looking at the diff, this is only used for
SPD_CUST for and for which you now always pass in 9600 as old_baud.
So just drop this.
> switch (priv->chip_type) {
> @@ -1346,8 +1348,12 @@ static u32 get_ftdi_divisor(struct tty_struct *tty,
> if (div_value == (u32)-1) {
> dev_dbg(dev, "%s - Baudrate (%d) requested is not supported\n",
> __func__, baud);
> - baud = 9600;
> + baud = old_baud ? old_baud : 9600;
Please avoid the ternary operator.
> div_value = ftdi_sio_baud_to_divisor(baud);
How can setting the old speed fail here? That should not be possible
after you checked for B0, right?
> + if (div_value == -1) {
Cast for consistency (unless you remove this).
> + baud = 9600;
> + div_value = ftdi_sio_baud_to_divisor(baud);
> + }
> div_okay = 0;
> }
> break;
> @@ -1356,8 +1362,11 @@ static u32 get_ftdi_divisor(struct tty_struct *tty,
> div_value = ftdi_232am_baud_to_divisor(baud);
> } else {
> dev_dbg(dev, "%s - Baud rate too high!\n", __func__);
> - baud = 9600;
> - div_value = ftdi_232am_baud_to_divisor(9600);
> + if (old_baud >= 183 && old_baud <= 3000000)
> + baud = old_baud;
> + else
> + baud = 9600;
> + div_value = ftdi_232am_baud_to_divisor(baud);
> div_okay = 0;
> }
> break;
> @@ -1379,9 +1388,12 @@ static u32 get_ftdi_divisor(struct tty_struct *tty,
> div_value = ftdi_232bm_baud_to_divisor(baud);
> } else {
> dev_dbg(dev, "%s - Baud rate too high!\n", __func__);
> - div_value = ftdi_232bm_baud_to_divisor(9600);
> + if (old_baud >= 183 && old_baud <= 3000000)
> + baud = old_baud;
> + else
> + baud = 9600;
> + div_value = ftdi_232bm_baud_to_divisor(baud);
> div_okay = 0;
> - baud = 9600;
> }
> break;
> case FT2232H: /* FT2232H chip */
> @@ -1393,9 +1405,17 @@ static u32 get_ftdi_divisor(struct tty_struct *tty,
> div_value = ftdi_232bm_baud_to_divisor(baud);
> } else {
> dev_dbg(dev, "%s - Baud rate too high!\n", __func__);
> - div_value = ftdi_232bm_baud_to_divisor(9600);
> + if (old_baud >= 183 && old_baud < 1200) {
> + baud = old_baud;
> + div_value = ftdi_232bm_baud_to_divisor(baud);
> + } else {
> + if (old_baud >= 1200 && old_baud <= 12000000)
> + baud = old_baud;
> + else
> + baud = 9600;
> + div_value = ftdi_2232h_baud_to_divisor(baud);
> + }
Please try to refactor this so that you don't have to open-code the same
test for baud as well as old_baud.
This function was hard to read already before this series and we should
not make it worse.
> div_okay = 0;
> - baud = 9600;
> }
> break;
> } /* priv->chip_type */
> @@ -1410,7 +1430,7 @@ static u32 get_ftdi_divisor(struct tty_struct *tty,
> return div_value;
> }
>
> -static int change_speed(struct tty_struct *tty, struct usb_serial_port *port)
> +static int change_speed(struct tty_struct *tty, struct usb_serial_port *port, speed_t old_baud)
> {
> struct ftdi_private *priv = usb_get_serial_port_data(port);
> u16 value;
> @@ -1418,7 +1438,7 @@ static int change_speed(struct tty_struct *tty, struct usb_serial_port *port)
> u32 index_value;
> int rv;
>
> - index_value = get_ftdi_divisor(tty, port);
> + index_value = get_ftdi_divisor(tty, port, old_baud);
> value = (u16)index_value;
> index = (u16)(index_value >> 16);
> if (priv->chip_type == FT2232C || priv->chip_type == FT2232H ||
> @@ -1541,7 +1561,7 @@ static int set_serial_info(struct tty_struct *tty, struct serial_struct *ss)
> if (priv->flags & ASYNC_SPD_MASK)
> dev_warn_ratelimited(&port->dev, "use of SPD flags is deprecated\n");
>
> - change_speed(tty, port);
> + change_speed(tty, port, 9600);
> }
> mutex_unlock(&priv->cfg_lock);
> return 0;
> @@ -2790,9 +2810,12 @@ static void ftdi_set_termios(struct tty_struct *tty,
> /* Drop RTS and DTR */
> clear_mctrl(port, TIOCM_DTR | TIOCM_RTS);
> } else {
> + speed_t old_baud =
> + old_termios ? tty_termios_baud_rate(old_termios) : 9600;
Use c_ospeed directly, and avoid the ternary operator.
> +
> /* set the baudrate determined before */
> mutex_lock(&priv->cfg_lock);
> - if (change_speed(tty, port))
> + if (change_speed(tty, port, old_baud))
But perhaps you should just pass in old_termios (or NULL in
set_serial_info()) so that you handle this in one place.
> dev_err(ddev, "%s urb failed to set baudrate\n", __func__);
> mutex_unlock(&priv->cfg_lock);
> /* Ensure RTS and DTR are raised when baudrate changed from 0 */
Johan
