Re: [PATCH v4 5/7] usb: serial: implement set_termios for F81232

[Johan Hovold <johan@kernel.org>]

On Fri, Jan 30, 2015 at 02:13:39PM +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.
> 
> Signed-off-by: Peter Hung <hpeter+linux_kernel@gmail.com>
> ---
>  drivers/usb/serial/f81232.c | 144 +++++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 137 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/usb/serial/f81232.c b/drivers/usb/serial/f81232.c
> index 12e1ae4..248f40d 100644
> --- a/drivers/usb/serial/f81232.c
> +++ b/drivers/usb/serial/f81232.c
> @@ -51,6 +51,10 @@ MODULE_DEVICE_TABLE(usb, id_table);
>  #define F81232_USB_TIMEOUT 3000
>  
>  #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_STATUS_REGISTER      (0x06 + SERIAL_BASE_ADDRESS)
>  struct f81232_private {
>  	spinlock_t lock;
> @@ -61,6 +65,20 @@ struct f81232_private {
>  	struct usb_serial_port *port;
>  };
>  
> +static inline int calc_baud_divisor(u32 baudrate)

No need for inline.

> +{
> +	u32 divisor, rem;
> +
> +	divisor = 115200L / baudrate;
> +	rem = 115200L % baudrate;

Use a define for the base baud rate. Is 115200 really the maximum baud
rate?
	
> +
> +	/* Round to nearest divisor */
> +	if (((rem * 2) >= baudrate) && (baudrate != 110))
> +		divisor++;

Can't you use DIV_ROUND_CLOSEST here as serial core does?

> +
> +	return divisor;
> +}
> +
>  static inline int f81232_get_register(struct usb_device *dev,
>  							  u16 reg, u8 *data)

No inline.

>  {
> @@ -84,6 +102,29 @@ static inline int f81232_get_register(struct usb_device *dev,
>  	return status;
>  }
>  
> +static inline int f81232_set_register(struct usb_device *dev,
> +							  u16 reg, u8 data)

Pass the usb-serial port instead of usb device here as well.

> +{
> +	int status;
> +
> +	status = usb_control_msg(dev,
> +			usb_sndctrlpipe(dev, 0),
> +			REGISTER_REQUEST,
> +			SET_REGISTER,
> +			reg,
> +			0,
> +			&data,
> +			1,

sizeof(data) for clarity?

> +			F81232_USB_TIMEOUT);
> +
> +	if (status < 0) {
> +		dev_dbg(&dev->dev,
> +			"%s status: %d\n", __func__, status);

dev_err, no line break

> +	}
> +
> +	return status;
> +}
> +
>  static void f81232_read_msr(struct f81232_private *priv)
>  {
>  	int status;
> @@ -240,15 +281,104 @@ static void f81232_break_ctl(struct tty_struct *tty, int break_state)
>  static void f81232_set_termios(struct tty_struct *tty,
>  		struct usb_serial_port *port, struct ktermios *old_termios)
>  {
> -	/* FIXME - Stubbed out for now */
> +	u16 divisor;
> +	u16 new_lcr = 0;

Why u16 for an 8-bit register?

> +	u8 data;
> +	int status;
> +	struct ktermios *termios = &tty->termios;
> +	struct usb_device *dev = port->serial->dev;
> +	unsigned int cflag = termios->c_cflag;

Use the cflag macros directly below (e.g. C_PARENB(tty)) and you won't
need this (or termios above).

>  
> -	/* Don't change anything if nothing has changed */
> -	if (old_termios && !tty_termios_hw_change(&tty->termios, old_termios))
> -		return;
> +	divisor = calc_baud_divisor(tty_get_baud_rate(tty));

You get a division by zero here of the baud rate is 0 (B0 is used to
drop DTR/RTS).

> +
> +	status = f81232_set_register(dev, LINE_CONTROL_REGISTER,
> +			 UART_LCR_DLAB); /* DLAB */
> +

No newline before testing return values (again, applies to whole
series).

> +	if (status < 0) {
> +		dev_dbg(&dev->dev,
> +			"%s status: %d line:%d\n", __func__, status, __LINE__);
> +	}

Use dev_err for errors throughout, but remember that you already log
errors in the accessor function.

> +
> +	status = f81232_set_register(dev, RECEIVE_BUFFER_REGISTER,
> +			 divisor & 0x00ff); /* low */
> +
> +	if (status < 0) {
> +		dev_dbg(&dev->dev,
> +			"%s status: %d line:%d\n", __func__, status, __LINE__);
> +	}
> +
> +	status = f81232_set_register(dev, INTERRUPT_ENABLE_REGISTER,
> +			 (divisor & 0xff00) >> 8); /* high */
> +
> +	if (status < 0) {
> +		dev_dbg(&dev->dev,
> +			"%s status: %d line:%d\n", __func__, status, __LINE__);
> +	}
> +
> +	status = f81232_set_register(dev, LINE_CONTROL_REGISTER, 0x00);
> +
> +	if (status < 0) {
> +		dev_dbg(&dev->dev,
> +			"%s status: %d line:%d\n", __func__, status, __LINE__);
> +	}

Perhaps factor the above out in a f81232_set_baudrate helper?

> +
> +	if (cflag & PARENB) {
> +		new_lcr |= UART_LCR_PARITY; /* default parity on/odd */
> +
> +		if (cflag & CMSPAR) {
> +			if (cflag & PARODD) {
> +				/* stick mark */
> +				new_lcr |= UART_LCR_SPAR;
> +			} else {
> +				 /* stick space */
> +				new_lcr |= (UART_LCR_EPAR | UART_LCR_SPAR);
> +			}
> +		} else {
> +			if (!(cflag & PARODD)) {
> +				/* even */
> +				new_lcr |= UART_LCR_EPAR;
> +			}
> +		}
> +	}

Looks like you could simplify the above to something like

	if (C_PARENB(tty) {
		lcr |= UART_LCR_PARITY;

		if (!C_PARODD(tty))
			lcr |= UART_LCR_EPAR

		if (C_CMSPAR(tty))
			lcr |= UART_LCR_SPAR;
	}

> +
> +	if (cflag & CSTOPB)
> +		new_lcr |= UART_LCR_STOP;
> +	else
> +		new_lcr &= ~UART_LCR_STOP;

No need to clear bits since you initialise to 0.

> +
> +	switch (cflag & CSIZE) {
> +	case CS5:
> +		new_lcr |= UART_LCR_WLEN5;
> +		break;
> +	case CS6:
> +		new_lcr |= UART_LCR_WLEN6;
> +		break;
> +	case CS7:
> +		new_lcr |= UART_LCR_WLEN7;
> +		break;
> +	default:
> +	case CS8:
> +		new_lcr |= UART_LCR_WLEN8;
> +		break;
> +	}
> +
> +	status |= f81232_set_register(dev, LINE_CONTROL_REGISTER, new_lcr);
> +
> +	/* fifo on, trigger8, clear TX/RX*/
> +	data = UART_FCR_TRIGGER_8 | UART_FCR_ENABLE_FIFO | UART_FCR_CLEAR_RCVR
> +		| UART_FCR_CLEAR_XMIT;
> +
> +	status |= f81232_set_register(dev, FIFO_CONTROL_REGISTER, data);
> +
> +	data = UART_IER_MSI | UART_IER_RLSI | UART_IER_THRI | UART_IER_RDI;
> +
> +	status |= f81232_set_register(dev,
> +			  INTERRUPT_ENABLE_REGISTER, 0xf); /* IER */
> +
> +	if (status < 0)
> +		dev_err(&port->dev, "LINE_CONTROL_REGISTER set error: %d\n",
> +			status);

Some of the above should only be needed when initialising (or opening)
the port and not on every set_termios, right?

>  
> -	/* Do the real work here... */
> -	if (old_termios)
> -		tty_termios_copy_hw(&tty->termios, old_termios);
>  }
>  
>  static int f81232_tiocmget(struct tty_struct *tty)

Johan