linux-kernel - Re: [PATCH 06/14] serial: tegra: report error to upper tty layer

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Date:   Tue, 13 Aug 2019 11:52:19 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Krishna Yarlagadda <kyarlagadda@...dia.com>
Cc:     gregkh@...uxfoundation.org, robh+dt@...nel.org,
        mark.rutland@....com, jonathanh@...dia.com, ldewangan@...dia.com,
        jslaby@...e.com, linux-serial@...r.kernel.org,
        devicetree@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Shardar Shariff Md <smohammed@...dia.com>
Subject: Re: [PATCH 06/14] serial: tegra: report error to upper tty layer

On Mon, Aug 12, 2019 at 04:58:15PM +0530, Krishna Yarlagadda wrote:
> Report overrun/parity/frame/break errors to top tty layer. Add support
> to ignore break character if IGNBRK is set.
> 
> Signed-off-by: Shardar Shariff Md <smohammed@...dia.com>
> Signed-off-by: Krishna Yarlagadda <kyarlagadda@...dia.com>
> ---
>  drivers/tty/serial/serial-tegra.c | 19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/tty/serial/serial-tegra.c b/drivers/tty/serial/serial-tegra.c
> index f6a3f4e..7ab81bb 100644
> --- a/drivers/tty/serial/serial-tegra.c
> +++ b/drivers/tty/serial/serial-tegra.c
> @@ -374,13 +374,21 @@ static char tegra_uart_decode_rx_error(struct tegra_uart_port *tup,
>  			tup->uport.icount.frame++;
>  			dev_err(tup->uport.dev, "Got frame errors\n");
>  		} else if (lsr & UART_LSR_BI) {
> -			dev_err(tup->uport.dev, "Got Break\n");
> -			tup->uport.icount.brk++;
> -			/* If FIFO read error without any data, reset Rx FIFO */
> +			/*
> +			 * Break error
> +			 * If FIFO read error without any data, reset Rx FIFO
> +			 */
>  			if (!(lsr & UART_LSR_DR) && (lsr & UART_LSR_FIFOE))
>  				tegra_uart_fifo_reset(tup, UART_FCR_CLEAR_RCVR);
> +			if (tup->uport.ignore_status_mask & UART_LSR_BI)
> +				return TTY_BREAK;
> +			flag = TTY_BREAK;
> +			tup->uport.icount.brk++;
> +			dev_err(tup->uport.dev, "Got Break\n");

I know this is preexisting, but why do we want to output an error
message in these cases. Isn't it perfectly legal for this to happen?

Thierry

>  		}
> +		uart_insert_char(&tup->uport, lsr, UART_LSR_OE, 0, flag);
>  	}
> +
>  	return flag;
>  }
>  
> @@ -562,6 +570,9 @@ static void tegra_uart_handle_rx_pio(struct tegra_uart_port *tup,
>  			break;
>  
>  		flag = tegra_uart_decode_rx_error(tup, lsr);
> +		if (flag != TTY_NORMAL)
> +			continue;
> +
>  		ch = (unsigned char) tegra_uart_read(tup, UART_RX);
>  		tup->uport.icount.rx++;
>  
> @@ -1224,6 +1235,8 @@ static void tegra_uart_set_termios(struct uart_port *u,
>  	/* Ignore all characters if CREAD is not set */
>  	if ((termios->c_cflag & CREAD) == 0)
>  		tup->uport.ignore_status_mask |= UART_LSR_DR;
> +	if (termios->c_iflag & IGNBRK)
> +		tup->uport.ignore_status_mask |= UART_LSR_BI;
>  
>  	spin_unlock_irqrestore(&u->lock, flags);
>  }
> -- 
> 2.7.4
> 

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