Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751819AbdHLTy5 (ORCPT ); Sat, 12 Aug 2017 15:54:57 -0400 Received: from metis.ext.4.pengutronix.de ([92.198.50.35]:41247 "EHLO metis.ext.4.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750973AbdHLTyz (ORCPT ); Sat, 12 Aug 2017 15:54:55 -0400 Date: Sat, 12 Aug 2017 21:54:51 +0200 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= To: Clemens Gruber Cc: linux-serial@vger.kernel.org, Greg Kroah-Hartman , Fabio Estevam , linux-kernel@vger.kernel.org, Ian Jamison Subject: Re: [PATCH] serial: imx: Improve PIO prevention if TX DMA has been started Message-ID: <20170812195451.2g65wifawouz4t7d@pengutronix.de> References: <20170812151210.10420-1-clemens.gruber@pqgruber.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20170812151210.10420-1-clemens.gruber@pqgruber.com> User-Agent: NeoMutt/20170113 (1.7.2) X-SA-Exim-Connect-IP: 2001:67c:670:100:5054:ff:fe2a:3aa X-SA-Exim-Mail-From: ukl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1803 Lines: 52 On Sat, Aug 12, 2017 at 05:12:10PM +0200, Clemens Gruber wrote: > The imx_transmit_buffer function should return if TX DMA has already > been started and not just skip over the buffer PIO write loop. (Which > did fix the initial problem, but could have unintentional side-effects) > > Tested on an i.MX6Q board with half-duplex RS-485 and with RS-232. > > Cc: Ian Jamison > Cc: Uwe-Kleine K?nig > Fixes: 514ab34dbad6 ("serial: imx: Prevent TX buffer PIO write when a > DMA has been started") AFAIK no newline in the Fixes: line. > Signed-off-by: Clemens Gruber > --- > drivers/tty/serial/imx.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c > index 80934e7bd67f..fce538eb8c77 100644 > --- a/drivers/tty/serial/imx.c > +++ b/drivers/tty/serial/imx.c > @@ -452,13 +452,14 @@ static inline void imx_transmit_buffer(struct imx_port *sport) > if (sport->dma_is_txing) { > temp |= UCR1_TDMAEN; > writel(temp, sport->port.membase + UCR1); > + return; > } else { > writel(temp, sport->port.membase + UCR1); > imx_dma_tx(sport); > } Shouldn't the return go here? Did you understand the problem? Can you say why this only hurts in RS485 half-duplex but not (as it seems) in regular rs232 mode? > } > > - while (!uart_circ_empty(xmit) && !sport->dma_is_txing && > + while (!uart_circ_empty(xmit) && > !(readl(sport->port.membase + uts_reg(sport)) & UTS_TXFULL)) { > /* send xmit->buf[xmit->tail] > * out the port here */ Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-K?nig | Industrial Linux Solutions | http://www.pengutronix.de/ |