Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933498AbcLMQ32 (ORCPT ); Tue, 13 Dec 2016 11:29:28 -0500 Received: from mail-wm0-f68.google.com ([74.125.82.68]:32952 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932784AbcLMQ2g (ORCPT ); Tue, 13 Dec 2016 11:28:36 -0500 From: Richard Genoud To: 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 , stable@vger.kernel.org (beware, this won't apply before 4.3) Subject: [PATCH] tty/serial: atmel_serial: BUG: stop DMA from transmitting in stop_tx Date: Tue, 13 Dec 2016 17:27:56 +0100 Message-Id: <20161213162756.16139-1-richard.genoud@gmail.com> X-Mailer: git-send-email 2.11.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1630 Lines: 48 If we don't disable the transmitter in atmel_stop_tx, the DMA buffer continues to send data until it is emptied. This cause problems with the flow control (CTS is asserted and data are still sent). So, disabling the transmitter in atmel_stop_tx is a sane thing to do. Tested on at91sam9g35-cm(DMA) Tested for regressions on sama5d2-xplained(Fifo) and at91sam9g20ek(PDC) Cc: (beware, this won't apply before 4.3) Signed-off-by: Richard Genoud --- drivers/tty/serial/atmel_serial.c | 11 +++++++++++ 1 file changed, 11 insertions(+) NB: this is not for the 4.10 merge window, I'm just sending it now to have some comments if someone is againts it. diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c index 168b10cad47b..f9d42de5ab2d 100644 --- a/drivers/tty/serial/atmel_serial.c +++ b/drivers/tty/serial/atmel_serial.c @@ -481,6 +481,14 @@ static void atmel_stop_tx(struct uart_port *port) /* disable PDC transmit */ atmel_uart_writel(port, ATMEL_PDC_PTCR, ATMEL_PDC_TXTDIS); } + + /* + * Disable the transmitter. + * This is mandatory when DMA is used, otherwise the DMA buffer + * is fully transmitted. + */ + atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXDIS); + /* Disable interrupts */ atmel_uart_writel(port, ATMEL_US_IDR, atmel_port->tx_done_mask); @@ -513,6 +521,9 @@ static void atmel_start_tx(struct uart_port *port) /* Enable interrupts */ atmel_uart_writel(port, ATMEL_US_IER, atmel_port->tx_done_mask); + + /* re-enable the transmitter */ + atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXEN); } /*