Re: [PATCH V2 2/3] tty: serial: fsl_lpuart: remove RTS/CTS control from set/get_mctrl

[Bhuvanchandra DV]

Hello,

On 06/08/2015 12:11 PM, Uwe Kleine-König wrote:
> Hello,
>
> On Mon, Jun 01, 2015 at 10:51:06AM +0530, Bhuvanchandra DV wrote:
> > The LPUART does not provide manual control of RTS/CTS signals,
> > those can only be controlled by the hardware directly. Therefore
> > manual control of those signals through mctrl can not be provided.
> > The current implementation enables/disables the automatic control,
> > which is not what mctrl should do, hence remove the incorrect
> > implementation.
> >
> > Signed-off-by: Bhuvanchandra DV <bhuvanchandra.dv@xxxxxxxxxxx>
> > ---
> >   drivers/tty/serial/fsl_lpuart.c | 63 +++++------------------------------------
> >   1 file changed, 7 insertions(+), 56 deletions(-)
> >
> > diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
> > index 08ce76f..532cfb7 100644
> > --- a/drivers/tty/serial/fsl_lpuart.c
> > +++ b/drivers/tty/serial/fsl_lpuart.c
> > @@ -822,64 +822,15 @@ static unsigned int lpuart32_tx_empty(struct uart_port *port)
> >
> >   static unsigned int lpuart_get_mctrl(struct uart_port *port)
> >   {
> > -	unsigned int temp = 0;
> > -	unsigned char reg;
> > -
> > -	reg = readb(port->membase + UARTMODEM);
> > -	if (reg & UARTMODEM_TXCTSE)
> > -		temp |= TIOCM_CTS;
> > -
> > -	if (reg & UARTMODEM_RXRTSE)
> > -		temp |= TIOCM_RTS;
> > -
> > -	return temp;
>  From reading the commit log I would expect that you only touch the
> set_mctrl function, but not get_mctrl. Assuming your code change is
> right, can you mention this in the commit log please? The bits
> UARTMODEM_TXCTSE and UARTMODEM_RXRTSE only control the automatic mode?
OK, will use 'get/set_mctrl' instead of 'mctrl' in the commit log.
Yes, those bits are only responsible for enabling/disabling the auto 
hardware flow control, not for controlling the RTS/CTS signals directly.
> What is the problem you're fixing here? I'm not sure how such an UART
> should be handled, but I imagine that you want to make use of automatic
> mode in some cases. Greg?
Fixing the implementation of hardware flow control wrt LPUART hardware.
> Best regards
> Uwe

Best regards,
Bhuvan
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