From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:45888 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750918AbdAQQNq (ORCPT ); Tue, 17 Jan 2017 11:13:46 -0500 Subject: Patch "tty/serial: atmel_serial: BUG: stop DMA from transmitting in stop_tx" has been added to the 4.4-stable tree To: richard.genoud@gmail.com, gregkh@linuxfoundation.org, nicolas.ferre@atmel.com Cc: , From: Date: Tue, 17 Jan 2017 17:11:39 +0100 Message-ID: <148466949922389@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled tty/serial: atmel_serial: BUG: stop DMA from transmitting in stop_tx to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: tty-serial-atmel_serial-bug-stop-dma-from-transmitting-in-stop_tx.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 89d8232411a85b9a6b12fd5da4d07d8a138a8e0c Mon Sep 17 00:00:00 2001 From: Richard Genoud Date: Tue, 13 Dec 2016 17:27:56 +0100 Subject: tty/serial: atmel_serial: BUG: stop DMA from transmitting in stop_tx From: Richard Genoud commit 89d8232411a85b9a6b12fd5da4d07d8a138a8e0c upstream. 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) Signed-off-by: Richard Genoud Acked-by: Nicolas Ferre Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/atmel_serial.c | 11 +++++++++++ 1 file changed, 11 insertions(+) --- a/drivers/tty/serial/atmel_serial.c +++ b/drivers/tty/serial/atmel_serial.c @@ -470,6 +470,14 @@ static void atmel_stop_tx(struct uart_po /* 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); @@ -502,6 +510,9 @@ static void atmel_start_tx(struct uart_p /* 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); } /* Patches currently in stable-queue which might be from richard.genoud@gmail.com are queue-4.4/tty-serial-atmel_serial-bug-stop-dma-from-transmitting-in-stop_tx.patch