Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1034280AbcJ0XN6 (ORCPT ); Thu, 27 Oct 2016 19:13:58 -0400 Received: from up.free-electrons.com ([163.172.77.33]:51119 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1034145AbcJ0XNz (ORCPT ); Thu, 27 Oct 2016 19:13:55 -0400 Date: Fri, 28 Oct 2016 01:13:31 +0200 From: Alexandre Belloni To: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= Cc: Richard Genoud , Nicolas Ferre , Greg Kroah-Hartman , Cyrille Pitchen , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, "#4 . 4+" Subject: Re: [PATCH v6] tty/serial: at91: fix hardware handshake on Atmel platforms Message-ID: <20161027231331.gngekbg22wfvnolr@piout.net> References: <20161027160406.25738-1-richard.genoud@gmail.com> <20161027180229.5faqrvxa2a4pos7i@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20161027180229.5faqrvxa2a4pos7i@pengutronix.de> User-Agent: NeoMutt/20161014 (1.7.1) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2201 Lines: 52 On 27/10/2016 at 20:02:29 +0200, Uwe Kleine-K?nig 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