linux-kernel - Re: [PATCH V9 4/4] USB: serial: f81232: implement break control

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Date:   Fri, 3 May 2019 08:59:17 +0200
From:   Johan Hovold <johan@...nel.org>
To:     "Ji-Ze Hong (Peter Hong)" <hpeter@...il.com>
Cc:     peter_hong@...tek.com.tw, johan@...nel.org,
        gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "Ji-Ze Hong (Peter Hong)" <hpeter+linux_kernel@...il.com>
Subject: Re: [PATCH V9 4/4] USB: serial: f81232: implement break control

On Tue, Apr 30, 2019 at 09:22:32AM +0800, Ji-Ze Hong (Peter Hong) wrote:
> Implement Fintek F81232 break on/off with LCR register.
> It's the same with 16550A LCR register layout.
> 
> Signed-off-by: Ji-Ze Hong (Peter Hong) <hpeter+linux_kernel@...il.com>
> ---

>  static void f81232_break_ctl(struct tty_struct *tty, int break_state)
>  {
> -	/* FIXME - Stubbed out for now */
> +	struct usb_serial_port *port = tty->driver_data;
> +	struct f81232_private *priv = usb_get_serial_port_data(port);
> +	int status;
>  
> -	/*
> -	 * break_state = -1 to turn on break, and 0 to turn off break
> -	 * see drivers/char/tty_io.c to see it used.
> -	 * last_set_data_urb_value NEVER has the break bit set in it.
> -	 */
> +	mutex_lock(&priv->lock);
> +
> +	if (break_state)
> +		priv->shadow_lcr |= UART_LCR_SBC;
> +	else
> +		priv->shadow_lcr &= ~UART_LCR_SBC;
> +
> +	status = f81232_set_register(port, LINE_CONTROL_REGISTER,
> +					priv->shadow_lcr);
> +	if (status)
> +		dev_err(&port->dev, "set break failed: %d\n", status);
> +
> +	mutex_unlock(&priv->lock);
>  }

> @@ -519,6 +530,7 @@ static int f81232_port_disable(struct usb_serial_port *port)
>  static void f81232_set_termios(struct tty_struct *tty,
>  		struct usb_serial_port *port, struct ktermios *old_termios)
>  {
> +	struct f81232_private *priv = usb_get_serial_port_data(port);
>  	u8 new_lcr = 0;
>  	int status = 0;
>  	speed_t baudrate;
> @@ -572,11 +584,16 @@ static void f81232_set_termios(struct tty_struct *tty,
>  		break;
>  	}
>  
> +	mutex_lock(&priv->lock);
> +
> +	new_lcr |= (priv->shadow_lcr & UART_LCR_SBC);
>  	status = f81232_set_register(port, LINE_CONTROL_REGISTER, new_lcr);
>  	if (status) {
>  		dev_err(&port->dev, "%s failed to set LCR: %d\n",
>  			__func__, status);
>  	}
> +
> +	mutex_unlock(&priv->lock);

You forgot to update shadow_lcr here so the line settings would be
corrupted (e.g set to 5 bit words) whenever a break is signalled.

Did you not test this version of the patch?

I added the missing update, but please test the code that's in my
usb-next branch in a minute and confirm everything works as expected.

All four patches now applied.

Thanks,
Johan