Re: [PATCH V7 08/11] USB: f81232: implement set_termios()

[Johan Hovold <johan@kernel.org>]

On Tue, Feb 24, 2015 at 06:16:23PM +0800, Peter Hung wrote:
> The original driver had do not any h/w change in driver.
> This patch implements with configure H/W for
> baud/parity/word length/stop bits functional in f81232_set_termios().
> 
> This patch also implement DTR/RTS control when baudrate B0.
> We drop DTR/RTS when B0, otherwise enable it.
> 
> Signed-off-by: Peter Hung <hpeter+linux_kernel@gmail.com>
> ---
>  drivers/usb/serial/f81232.c | 106 ++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 102 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/usb/serial/f81232.c b/drivers/usb/serial/f81232.c
> index f5c9060..0c96b9a 100644
> --- a/drivers/usb/serial/f81232.c
> +++ b/drivers/usb/serial/f81232.c
> @@ -31,14 +31,19 @@ static const struct usb_device_id id_table[] = {
>  };
>  MODULE_DEVICE_TABLE(usb, id_table);
>  
> +/* Maximum baudrate for F81232 */
> +#define F81232_MAX_BAUDRATE	115200
> +
>  /* USB Control EP parameter */
>  #define F81232_REGISTER_REQUEST	0xA0
>  #define F81232_GET_REGISTER	0xc0
>  #define F81232_SET_REGISTER	0x40
>  
>  #define SERIAL_BASE_ADDRESS	0x0120
> +#define RECEIVE_BUFFER_REGISTER	(0x00 + SERIAL_BASE_ADDRESS)
>  #define INTERRUPT_ENABLE_REGISTER	(0x01 + SERIAL_BASE_ADDRESS)
>  #define FIFO_CONTROL_REGISTER	(0x02 + SERIAL_BASE_ADDRESS)
> +#define LINE_CONTROL_REGISTER	(0x03 + SERIAL_BASE_ADDRESS)
>  #define MODEM_CONTROL_REGISTER	(0x04 + SERIAL_BASE_ADDRESS)
>  #define MODEM_STATUS_REGISTER	(0x06 + SERIAL_BASE_ADDRESS)
>  
> @@ -64,6 +69,14 @@ struct f81232_private {
>  	struct usb_serial_port *port;
>  };
>  
> +static int calc_baud_divisor(u32 baudrate)
> +{
> +	if (!baudrate)
> +		return 0;

Check no longer needed since you added the check at the call site. Just
add a comment. In fact it look like you can get rid of this function
now.

> +	else
> +		return DIV_ROUND_CLOSEST(F81232_MAX_BAUDRATE, baudrate);
> +}
> +
>  static int f81232_get_register(struct usb_serial_port *port, u16 reg, u8 *data)
>  {
>  	int status;
> @@ -369,6 +382,52 @@ static void f81232_break_ctl(struct tty_struct *tty, int break_state)
>  	 */
>  }
>  
> +static void f81232_set_baudrate(struct usb_serial_port *port, int baudrate)
> +{
> +	u8 divisor, lcr;
> +	int status = 0;
> +
> +	if (!baudrate)
> +		return;
> +
> +	divisor = calc_baud_divisor(baudrate);
> +
> +	status = f81232_get_register(port, LINE_CONTROL_REGISTER,
> +			 &lcr); /* get LCR */
> +	if (status) {
> +		dev_err(&port->dev, "%s failed to get LCR: %d\n",
> +			__func__, status);
> +	}
> +
> +	status = f81232_set_register(port, LINE_CONTROL_REGISTER,
> +			 lcr | UART_LCR_DLAB); /* Enable DLAB */
> +	if (status) {
> +		dev_err(&port->dev, "%s failed to set DLAB: %d\n",
> +			__func__, status);
> +	}
> +
> +	status = f81232_set_register(port, RECEIVE_BUFFER_REGISTER,
> +			 divisor & 0x00ff); /* low */
> +	if (status) {
> +		dev_err(&port->dev, "%s failed to set baudrate MSB: %d\n",
> +			__func__, status);
> +	}
> +
> +	status = f81232_set_register(port, INTERRUPT_ENABLE_REGISTER,
> +			 (divisor & 0xff00) >> 8); /* high */
> +	if (status) {
> +		dev_err(&port->dev, "%s failed to set baudrate LSB: %d\n",
> +			__func__, status);
> +	}
> +
> +	status = f81232_set_register(port, LINE_CONTROL_REGISTER,
> +			lcr & ~UART_LCR_DLAB);
> +	if (status) {
> +		dev_err(&port->dev, "%s failed to set DLAB: %d\n",
> +			__func__, status);
> +	}
> +}

Again, what about the error handling? No need to continue setting the
other registers should the first one fail, right? And you always want to
restore LCR to its previous value.

> +
>  static int f81232_port_enable(struct usb_serial_port *port, int enable)
>  {
>  	u8 data = 0;
> @@ -399,15 +458,54 @@ static int f81232_port_enable(struct usb_serial_port *port, int enable)
>  static void f81232_set_termios(struct tty_struct *tty,
>  		struct usb_serial_port *port, struct ktermios *old_termios)
>  {
> -	/* FIXME - Stubbed out for now */
> +	u8 new_lcr = 0;
> +	int status = 0;
> +
>  
>  	/* Don't change anything if nothing has changed */
>  	if (old_termios && !tty_termios_hw_change(&tty->termios, old_termios))
>  		return;
>  
> -	/* Do the real work here... */
> -	if (old_termios)
> -		tty_termios_copy_hw(&tty->termios, old_termios);
> +	if (C_BAUD(tty) == B0)
> +		f81232_set_mctrl(port, 0, TIOCM_DTR | TIOCM_RTS);
> +	else if (old_termios && (old_termios->c_cflag & CBAUD) == B0)
> +		f81232_set_mctrl(port, TIOCM_DTR | TIOCM_RTS, 0);
> +
> +	f81232_set_baudrate(port, tty_get_baud_rate(tty));

Check for B0 here instead of in the helper.

And what about unsupported baudrates (e.g. > 115200 baud)? You should
return the baudrate actually used in that case using
tty_termios_encode_baud_rate.

Johan