Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759974AbcJ1K4d (ORCPT ); Fri, 28 Oct 2016 06:56:33 -0400 Received: from mail-oi0-f68.google.com ([209.85.218.68]:34117 "EHLO mail-oi0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755461AbcJ1K4b (ORCPT ); Fri, 28 Oct 2016 06:56:31 -0400 MIME-Version: 1.0 In-Reply-To: <20161028095151.f24lhelfknzrpy6c@pengutronix.de> References: <20161027160406.25738-1-richard.genoud@gmail.com> <20161027180229.5faqrvxa2a4pos7i@pengutronix.de> <20161027231331.gngekbg22wfvnolr@piout.net> <20161028095151.f24lhelfknzrpy6c@pengutronix.de> From: Richard Genoud Date: Fri, 28 Oct 2016 12:56:09 +0200 Message-ID: Subject: Re: [PATCH v6] tty/serial: at91: fix hardware handshake on Atmel platforms To: =?UTF-8?Q?Uwe_Kleine=2DK=C3=B6nig?= , Greg Kroah-Hartman Cc: Alexandre Belloni , Nicolas Ferre , "linux-kernel@vger.kernel.org" , "#4 . 4+" , "linux-serial@vger.kernel.org" , Cyrille Pitchen , "linux-arm-kernel@lists.infradead.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by mail.home.local id u9SAuqN4014520 Content-Length: 3309 Lines: 72 2016-10-28 11:51 GMT+02:00 Uwe Kleine-König : > 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? Actually, a machine with a FIFO and without CTS didn't even exist at the time of the breaking commit (v4.0), the FIFO handling was introduced later, so it's not even a regression ! > 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 > > Best regards > Uwe Thanks ! Greg, could you take this in your tree ? regards, Richard.