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SubjectRE: [PATCH 06/14] serial: tegra: report error to upper tty layer
Date
> -----Original Message-----
> From: Thierry Reding <thierry.reding@gmail.com>
> Sent: Tuesday, August 13, 2019 3:22 PM
> To: Krishna Yarlagadda <kyarlagadda@nvidia.com>
> Cc: gregkh@linuxfoundation.org; robh+dt@kernel.org;
> mark.rutland@arm.com; Jonathan Hunter <jonathanh@nvidia.com>; Laxman
> Dewangan <ldewangan@nvidia.com>; jslaby@suse.com; linux-
> serial@vger.kernel.org; devicetree@vger.kernel.org; linux-
> tegra@vger.kernel.org; linux-kernel@vger.kernel.org; Shardar Mohammed
> <smohammed@nvidia.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@nvidia.com>
> > Signed-off-by: Krishna Yarlagadda <kyarlagadda@nvidia.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
>
It is valid to have breaks for sysrq requests. But they also indicate possible mismatch in baud rate. So warning user as this could be potential issue. I will change this to dev_dbg to avoid spamming user in valid cases.

KY
> > }
> > + 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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