From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760037AbbKTMNr (ORCPT ); Fri, 20 Nov 2015 07:13:47 -0500 Received: from mail-ig0-f175.google.com ([209.85.213.175]:37170 "EHLO mail-ig0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760022AbbKTMNp (ORCPT ); Fri, 20 Nov 2015 07:13:45 -0500 Subject: Re: [PATH RESEND v2 03/10] tty: xuartps: Always enable transmitter in start_tx To: Soren Brinkmann , Greg Kroah-Hartman , Jiri Slaby References: <1447963344-16266-1-git-send-email-soren.brinkmann@xilinx.com> <1447963344-16266-4-git-send-email-soren.brinkmann@xilinx.com> Cc: linux-arm-kernel@lists.infradead.org, Michal Simek , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org From: Peter Hurley Message-ID: <564F0E75.5020100@hurleysoftware.com> Date: Fri, 20 Nov 2015 07:13:41 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <1447963344-16266-4-git-send-email-soren.brinkmann@xilinx.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/19/2015 03:02 PM, Soren Brinkmann wrote: > start_tx must start transmitting characters. Regardless of the state of > the circular buffer, always enable the transmitter hardware. Why? Does cdns_uart_stop_tx() actually stop the transmitter so that data remains in the transmitter? > Signed-off-by: Soren Brinkmann > --- > drivers/tty/serial/xilinx_uartps.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c > index 2c98c357d9a0..df6778d17949 100644 > --- a/drivers/tty/serial/xilinx_uartps.c > +++ b/drivers/tty/serial/xilinx_uartps.c > @@ -512,9 +512,6 @@ static void cdns_uart_start_tx(struct uart_port *port) > { > unsigned int status, numbytes = port->fifosize; > > - if (uart_circ_empty(&port->state->xmit) || uart_tx_stopped(port)) > - return; The test for tx stopped needs to remain; otherwise, transmission will restart even if the tty has been stopped (for example by userspace or IXON software flow control). Regards, Peter Hurley > - > /* > * Set the TX enable bit and clear the TX disable bit to enable the > * transmitter. > @@ -524,6 +521,9 @@ static void cdns_uart_start_tx(struct uart_port *port) > status |= CDNS_UART_CR_TX_EN; > writel(status, port->membase + CDNS_UART_CR_OFFSET); > > + if (uart_circ_empty(&port->state->xmit) || uart_tx_stopped(port)) > + return; > + > while (numbytes-- && ((readl(port->membase + CDNS_UART_SR_OFFSET) & > CDNS_UART_SR_TXFULL)) != CDNS_UART_SR_TXFULL) { > /* Break if no more data available in the UART buffer */ >