[PATCH] mxs: uart: allow setting RTS from software

[PATCH] mxs: uart: allow setting RTS from software

[Steffen Trumtrar]

With the patch "serial: mxs-auart: fix the wrong RTS hardware flow control" the
mainline mxs-uart driver now sets RTSEN only when hardware flow control is
enabled via software. It is not possible any longer to set RTS manually via
software. However, the manual modification is a valid operation.
Regain the possibility to set RTS via software and only set RTSEN when hardware
flow control is explicitly enabled via settermios cflag CRTSCTS.

Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
---
 drivers/tty/serial/mxs-auart.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/mxs-auart.c b/drivers/tty/serial/mxs-auart.c
index 6db23b0..9b62c4b 100644
--- a/drivers/tty/serial/mxs-auart.c
+++ b/drivers/tty/serial/mxs-auart.c
@@ -412,10 +412,12 @@ static void mxs_auart_set_mctrl(struct uart_port *u, unsigned mctrl)
 
 	u32 ctrl = readl(u->membase + AUART_CTRL2);
 
-	ctrl &= ~AUART_CTRL2_RTSEN;
+	ctrl &= ~(AUART_CTRL2_RTSEN | AUART_CTRL2_RTS);
 	if (mctrl & TIOCM_RTS) {
 		if (tty_port_cts_enabled(&u->state->port))
 			ctrl |= AUART_CTRL2_RTSEN;
+		else
+			ctrl |= AUART_CTRL2_RTS;
 	}
 
 	s->ctrl = mctrl;
@@ -678,6 +680,10 @@ static void mxs_auart_settermios(struct uart_port *u,
 		}
 		ctrl2 |= AUART_CTRL2_CTSEN | AUART_CTRL2_RTSEN;
 	} else {
+		u->flags |= ASYNC_CTS_FLOW;
+		ctrl2 |= AUART_CTRL2_CTSEN | AUART_CTRL2_RTSEN;
+	} else {
+		u->flags &= ~ASYNC_CTS_FLOW;
 		ctrl2 &= ~(AUART_CTRL2_CTSEN | AUART_CTRL2_RTSEN);
 	}
 
-- 
1.7.10.4

[PATCH] mxs: uart: allow setting RTS from software

[Huang Shijie]

? 2012?12?13? 00:31, Steffen Trumtrar ??:
> With the patch "serial: mxs-auart: fix the wrong RTS hardware flow control" the
> mainline mxs-uart driver now sets RTSEN only when hardware flow control is
> enabled via software. It is not possible any longer to set RTS manually via
> software. However, the manual modification is a valid operation.
> Regain the possibility to set RTS via software and only set RTSEN when hardware
Is there any user case to set the RTS via software?
I am confused at this.
> flow control is explicitly enabled via settermios cflag CRTSCTS.
>
> Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
> ---
>  drivers/tty/serial/mxs-auart.c |    8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/tty/serial/mxs-auart.c b/drivers/tty/serial/mxs-auart.c
> index 6db23b0..9b62c4b 100644
> --- a/drivers/tty/serial/mxs-auart.c
> +++ b/drivers/tty/serial/mxs-auart.c
> @@ -412,10 +412,12 @@ static void mxs_auart_set_mctrl(struct uart_port *u, unsigned mctrl)
>  
>  	u32 ctrl = readl(u->membase + AUART_CTRL2);
>  
> -	ctrl &= ~AUART_CTRL2_RTSEN;
> +	ctrl &= ~(AUART_CTRL2_RTSEN | AUART_CTRL2_RTS);
>  	if (mctrl & TIOCM_RTS) {
>  		if (tty_port_cts_enabled(&u->state->port))
>  			ctrl |= AUART_CTRL2_RTSEN;
> +		else
> +			ctrl |= AUART_CTRL2_RTS;
>  	}
>  
>  	s->ctrl = mctrl;
> @@ -678,6 +680,10 @@ static void mxs_auart_settermios(struct uart_port *u,
>  		}
>  		ctrl2 |= AUART_CTRL2_CTSEN | AUART_CTRL2_RTSEN;
>  	} else {
> +		u->flags |= ASYNC_CTS_FLOW;
> +		ctrl2 |= AUART_CTRL2_CTSEN | AUART_CTRL2_RTSEN;
> +	} else {
> +		u->flags &= ~ASYNC_CTS_FLOW;
bug.

Your code adds TWO "else" here.

thanks
Huang Shijie
>  		ctrl2 &= ~(AUART_CTRL2_CTSEN | AUART_CTRL2_RTSEN);
>  	}
>  

[PATCH] mxs: uart: allow setting RTS from software

[Steffen Trumtrar]

Hi,

On Thu, Dec 13, 2012 at 10:20:27AM +0800, Huang Shijie wrote:
> ? 2012?12?13? 00:31, Steffen Trumtrar ??:
> > With the patch "serial: mxs-auart: fix the wrong RTS hardware flow control" the
> > mainline mxs-uart driver now sets RTSEN only when hardware flow control is
> > enabled via software. It is not possible any longer to set RTS manually via
> > software. However, the manual modification is a valid operation.
> > Regain the possibility to set RTS via software and only set RTSEN when hardware
> Is there any user case to set the RTS via software?
> I am confused at this.

there are cases where the RTS is used in a non-standard way. And the always-on
hardware flowcontrol breaks these (e.g. Echelon FT5000).
And as stated in the commit message, it is a valid operation to use software
flow control.

> > flow control is explicitly enabled via settermios cflag CRTSCTS.
> >
> > Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
> > ---
> >  drivers/tty/serial/mxs-auart.c |    8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/tty/serial/mxs-auart.c b/drivers/tty/serial/mxs-auart.c
> > index 6db23b0..9b62c4b 100644
> > --- a/drivers/tty/serial/mxs-auart.c
> > +++ b/drivers/tty/serial/mxs-auart.c
> > @@ -412,10 +412,12 @@ static void mxs_auart_set_mctrl(struct uart_port *u, unsigned mctrl)
> >  
> >  	u32 ctrl = readl(u->membase + AUART_CTRL2);
> >  
> > -	ctrl &= ~AUART_CTRL2_RTSEN;
> > +	ctrl &= ~(AUART_CTRL2_RTSEN | AUART_CTRL2_RTS);
> >  	if (mctrl & TIOCM_RTS) {
> >  		if (tty_port_cts_enabled(&u->state->port))
> >  			ctrl |= AUART_CTRL2_RTSEN;
> > +		else
> > +			ctrl |= AUART_CTRL2_RTS;
> >  	}
> >  
> >  	s->ctrl = mctrl;
> > @@ -678,6 +680,10 @@ static void mxs_auart_settermios(struct uart_port *u,
> >  		}
> >  		ctrl2 |= AUART_CTRL2_CTSEN | AUART_CTRL2_RTSEN;
> >  	} else {
> > +		u->flags |= ASYNC_CTS_FLOW;
> > +		ctrl2 |= AUART_CTRL2_CTSEN | AUART_CTRL2_RTSEN;
> > +	} else {
> > +		u->flags &= ~ASYNC_CTS_FLOW;
> bug.
> 
> Your code adds TWO "else" here.
> 

Oops, wrong merge resolution. Will fix that.

Regards,
Steffen

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[PATCH] mxs: uart: allow setting RTS from software

[Ben Hutchings]

On Wed, Dec 12, 2012 at 05:31:53PM +0100, Steffen Trumtrar wrote:
> With the patch "serial: mxs-auart: fix the wrong RTS hardware flow control" the
> mainline mxs-uart driver now sets RTSEN only when hardware flow control is
> enabled via software. It is not possible any longer to set RTS manually via
> software. However, the manual modification is a valid operation.
> Regain the possibility to set RTS via software and only set RTSEN when hardware
> flow control is explicitly enabled via settermios cflag CRTSCTS.
> 
> Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
[...]

This is not the correct way to submit a patch to stable.  See
Documentation/stable_kernel_rules.txt

Ben.

-- 
Ben Hutchings
We get into the habit of living before acquiring the habit of thinking.
                                                              - Albert Camus