Re: [PATCH] serial: imx: Add Rx Fifo overrun error message

[Alexander Stein <alexander.stein@systec-electronic.com>]

On Tuesday 12 March 2013 08:46:23, Greg Kroah-Hartman wrote:
> On Mon, Mar 11, 2013 at 11:27:08AM +0100, Alexander Stein wrote:
> > Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>
> 
> No description of what you are doing in the changelog area?

I can be more verbose here in a v2.

> > ---
> >  drivers/tty/serial/imx.c | 14 ++++++++++++++
> >  1 file changed, 14 insertions(+)
> > 
> > diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> > index 147c9e1..fe72099 100644
> > --- a/drivers/tty/serial/imx.c
> > +++ b/drivers/tty/serial/imx.c
> > @@ -449,6 +449,13 @@ static void imx_start_tx(struct uart_port *port)
> >  		temp &= ~(UCR1_RRDYEN);
> >  		writel(temp, sport->port.membase + UCR1);
> >  	}
> > +	/* Clear any pending ORE flag before enabling interrupt */
> > +	temp = readl(sport->port.membase + USR2);
> > +	writel(temp | USR2_ORE, sport->port.membase + USR2);
> > +
> > +	temp = readl(sport->port.membase + UCR4);
> > +	temp |= UCR4_OREN;
> > +	writel(temp, sport->port.membase + UCR4);
> 
> This seems like a bugfix, right?  Different than what you put in the
> Subject line above.

I would not see this as a bugfix. It enables the overrun interrupt which can be tested in the interrupt handler (see below).

> >  
> >  	temp = readl(sport->port.membase + UCR1);
> >  	writel(temp | UCR1_TXMPTYEN, sport->port.membase + UCR1);
> > @@ -582,6 +589,7 @@ static irqreturn_t imx_int(int irq, void *dev_id)
> >  {
> >  	struct imx_port *sport = dev_id;
> >  	unsigned int sts;
> > +	unsigned int sts2;
> >  
> >  	sts = readl(sport->port.membase + USR1);
> >  
> > @@ -598,6 +606,12 @@ static irqreturn_t imx_int(int irq, void *dev_id)
> >  	if (sts & USR1_AWAKE)
> >  		writel(USR1_AWAKE, sport->port.membase + USR1);
> >  
> > +	sts2 = readl(sport->port.membase + USR2);
> > +	if (sts2 & USR2_ORE) {
> > +		dev_err(sport->port.dev, "Rx FIFO overrun\n");
> 
> Why?  What can a user now do about this?  Will this flood the syslog?

I have next to no knowledge on tty, so I don't know much how a user can be notified on a serial device that characters have been dropped. If this occurs very often, it will flood your syslog. Until now it is the only way to inform the user at all.

Best regards,
Alexander