On Fri, Oct 28, 2016 at 01:13:31AM +0200, Alexandre Belloni wrote:
> On 27/10/2016 at 20:02:29 +0200, Uwe Kleine-König wrote :
> > Hello Richard,
> >
> > On Thu, Oct 27, 2016 at 06:04:06PM +0200, Richard Genoud wrote:
> > > diff --git a/drivers/tty/serial/atmel_serial.c
> > > b/drivers/tty/serial/atmel_serial.c
> > > index fd8aa1f4ba78..168b10cad47b 100644
> > > --- a/drivers/tty/serial/atmel_serial.c
> > > +++ b/drivers/tty/serial/atmel_serial.c
> > > @@ -2132,11 +2132,29 @@ static void atmel_set_termios(struct uart_port
> > > *port, struct ktermios *termios,
> > > mode |= ATMEL_US_USMODE_RS485;
> > > } else if (termios->c_cflag & CRTSCTS) {
> > > /* RS232 with hardware handshake (RTS/CTS) */
> > > - if (atmel_use_dma_rx(port) && !atmel_use_fifo(port)) {
> > > - dev_info(port->dev, "not enabling hardware flow control
> > > because DMA is used");
> > > - termios->c_cflag &= ~CRTSCTS;
> > > - } else {
> > > + if (atmel_use_fifo(port) &&
> > > + !mctrl_gpio_to_gpiod(atmel_port->gpios, UART_GPIO_CTS)) {
> > > + /*
> > > + * with ATMEL_US_USMODE_HWHS set, the controller will
> > > + * be able to drive the RTS pin high/low when the RX
> > > + * FIFO is above RXFTHRES/below RXFTHRES2.
> > > + * It will also disable the transmitter when the CTS
> > > + * pin is high.
> > > + * This mode is not activated if CTS pin is a GPIO
> > > + * because in this case, the transmitter is always
> > > + * disabled (there must be an internal pull-up
> > > + * responsible for this behaviour).
> > > + * If the RTS pin is a GPIO, the controller won't be
> > > + * able to drive it according to the FIFO thresholds,
> > > + * but it will be handled by the driver.
> > > + */
> > > mode |= ATMEL_US_USMODE_HWHS;
> >
> > You use
> >
> > !mctrl_gpio_to_gpiod(atmel_port->gpios, UART_GPIO_CTS)
> >
> > as indicator that the cts mode of the respective pin is used. Is this
> > reliable? (It's not if there are machines that don't use CTS, neither as
> > gpio nor using the hardware function.) Maybe this needs a dt property to
> > indicate that there is no (hw)handshaking available?
> >
>
> We had a call today were we agreed that this should be added in a future
> patch. Let's fix the regression for now.
A machine without CTS (neither gpio nor hw function) used to work fine
before the breaking commit, right? So this case is part of the
regression and needs a fix?
Anyhow, this probably shouldn't stop the commit entering mainline
because there are probably very few such machines (if any).
So:
Acked-by: Uwe Kleine-König <u.kleine-koe...@pengutronix.de>
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |
