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.
--
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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