From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755892AbcI0OOX (ORCPT ); Tue, 27 Sep 2016 10:14:23 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:35987 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755657AbcI0OOK (ORCPT ); Tue, 27 Sep 2016 10:14:10 -0400 From: Richard Genoud To: =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= , Nicolas Ferre , Alexandre Belloni , Greg Kroah-Hartman , Cyrille Pitchen Cc: linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Richard Genoud Subject: [PATCHv3 3/3] tty/serial: at91: fix hardware handshake on SAM9x5 (without GPIOs) Date: Tue, 27 Sep 2016 16:13:13 +0200 Message-Id: <20160927141313.27668-4-richard.genoud@gmail.com> X-Mailer: git-send-email 2.10.0 In-Reply-To: <20160927141313.27668-1-richard.genoud@gmail.com> References: <20160927141313.27668-1-richard.genoud@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit 1cf6e8fc8341 ("tty/serial: at91: fix RTS line management when hardware handshake is enabled") broke the hardware handshake on SAM9x5 platforms. On Atmel platforms, the USART can only handle the handware handshake (ATMEL_US_USMODE_HWHS) if FIFOs or PDC are used. Thus, ATMEL_US_USMODE_HWHS mode should only be used in this case. For SAM9x5, there's no FIFOs nor PDC for the USART, so the mode should be ATMEL_US_USMODE_NORMAL and the RTS pin should be controlled by the driver. NB: -stable is not Cced because it doesn't cleanly apply on 4.1+ Tested on SAM9G35-CM with and without DMA Signed-off-by: Richard Genoud Fixes: 1cf6e8fc8341 ("tty/serial: at91: fix RTS line management when hardware handshake is enabled") --- drivers/tty/serial/atmel_serial.c | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-) diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c index 14467d5e060b..f644d5dcf6d1 100644 --- a/drivers/tty/serial/atmel_serial.c +++ b/drivers/tty/serial/atmel_serial.c @@ -2131,19 +2131,23 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios, port->rs485.delay_rts_after_send); mode |= ATMEL_US_USMODE_RS485; } else if ((termios->c_cflag & CRTSCTS) && - !mctrl_gpio_use_rtscts(atmel_port->gpios)) { + !mctrl_gpio_use_rtscts(atmel_port->gpios) && + (atmel_use_pdc_rx(port) || atmel_use_fifo(port))) { /* - * RS232 with hardware handshake (RTS/CTS) - * handled by the controller. + * Automatic hardware handshake (RTS/CTS) only work with + * FIFOs or PDC. + * Meaning that on SAM9x5 the controller can't handle + * the hardware handshake (no FIFOs nor PDC on these platforms). */ - 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 { - mode |= ATMEL_US_USMODE_HWHS; - } + mode |= ATMEL_US_USMODE_HWHS; } else { - /* RS232 without hardware handshake or controlled by GPIOs */ + /* + * Other cases are: + * - RS232 without hardware handshake + * - RS232 with hardware handshake and: + * - controller unable to handle CTS/RTS by itself + * - or CTS/RTS handled by GPIOs + */ mode |= ATMEL_US_USMODE_NORMAL; }