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x-vs=clean score=0 state=0 X-ME-VSCategory: clean X-CM-Envelope: MS4wfMxKzhhwqB0p96+TC1YEsO461a28nlLtbkSjhxzMeHiavZKZAvi2PhaivHil2Fhcp4Cplaj+MIbyQsvuICOPAGLoItfs0UhKVyuzGFhqlX4LEnZZTJsA LExj3NvtbvnUi34qDHNwhftkO2hokdQzn2eqg1PWGAX0XpTSdfjqE82v1w61+dj3fv8jVp5vp9n94J5rnQmXy8vG5tgimN9rcbZg0B9KIMqFJvkV8wvpRVg/ X-CM-Analysis: v=2.3 cv=E8HjW5Vl c=1 sm=1 tr=0 a=UK1r566ZdBxH71SXbqIOeA==:117 a=UK1r566ZdBxH71SXbqIOeA==:17 a=IkcTkHD0fZMA:10 a=xqWC_Br6kY4A:10 a=Kd1tUaAdevIA:10 a=VwQbUJbxAAAA:8 a=hRcl7-O5eJPR_diQkmEA:9 a=QEXdDO2ut3YA:10 a=x8gzFH9gYPwA:10 a=AjGcO6oz07-iQ99wixmX:22 X-ME-CMScore: 0 X-ME-CMCategory: none Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752707AbeDRPaq (ORCPT ); Wed, 18 Apr 2018 11:30:46 -0400 Received: from mail.kmu-office.ch ([178.209.48.109]:38282 "EHLO mail.kmu-office.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752634AbeDRPaq (ORCPT ); Wed, 18 Apr 2018 11:30:46 -0400 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Date: Wed, 18 Apr 2018 17:30:42 +0200 From: Stefan Agner To: =?UTF-8?Q?Uwe_Kleine-K=C3=B6nig?= Cc: gregkh@linuxfoundation.org, lukas@wunner.de, jslaby@suse.com, linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] serial: imx: warn user when using unsupported configuration In-Reply-To: <20180418145341.xwsah7spyfazcb63@pengutronix.de> References: <20180418140638.19331-1-stefan@agner.ch> <20180418145341.xwsah7spyfazcb63@pengutronix.de> Message-ID: <6cdfd27073006d0959c21eca23fa56e1@agner.ch> User-Agent: Roundcube Webmail/1.3.4 X-Remote-Spamd-Result: default: False [-2.12 / 15.00]; RCVD_TLS_ALL(0.00)[]; ASN(0.00)[asn:29691, ipnet:2a02:418::/29, country:CH]; RCVD_COUNT_ZERO(0.00)[0]; RCPT_COUNT_FIVE(0.00)[6]; FROM_HAS_DN(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; TO_DN_SOME(0.00)[]; MIME_GOOD(-0.10)[text/plain]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; BAYES_HAM(-2.02)[95.20%]; ARC_NA(0.00)[]; DKIM_SIGNED(0.00)[] Sender: linux-serial-owner@vger.kernel.org X-Mailing-List: linux-serial@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On 18.04.2018 16:53, Uwe Kleine-König wrote: > On Wed, Apr 18, 2018 at 04:06:38PM +0200, Stefan Agner wrote: >> When using half-duplex mode (which disables receiver during txing) >> the RTS signal cannot be driven low during transmission. This seems >> to be a limitation of the i.MX UART IP: The RTS (CTS_B) signal is >> controlled by the receiver. When the receiver is disabled, the >> signal stays in UART logic idle state which is high... >> >> If SER_RS485_RTS_ON_SEND is used, RTS needs to be high active during >> transmission. Since this is the default state of the RTS (CTS_B) >> signal when the receiver is off, half-duplex mode in this >> configuration works fine. >> >> However, a low-active RTS signal (flag SER_RS485_RTS_ON_SEND not set) >> cannot be generated when the receiver is turned off. >> >> Print an error if the user selects this unsupported configuration >> (both SER_RS485_RTS_ON_SEND and SER_RS485_RX_DURING_TX unset) and >> configure the closest working configuration (set the >> SER_RS485_RX_DURING_TX flag). >> >> Signed-off-by: Stefan Agner >> --- >> Changes since v1: >> - Consistently check for sport->have_rtscts && !(rs485conf->flags & >> SER_RS485_RTS_ON_SEND) >> - Don't break printed message >> >> drivers/tty/serial/imx.c | 15 +++++++++++++++ >> 1 file changed, 15 insertions(+) >> >> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c >> index 91f3a1a5cb7f..1c1080fc8084 100644 >> --- a/drivers/tty/serial/imx.c >> +++ b/drivers/tty/serial/imx.c >> @@ -1833,6 +1833,11 @@ static int imx_uart_rs485_config(struct uart_port *port, >> rs485conf->flags &= ~SER_RS485_ENABLED; >> >> if (rs485conf->flags & SER_RS485_ENABLED) { >> + /* Enable receiver if low-active RTS signal is requested */ >> + if (sport->have_rtscts && >> + !(rs485conf->flags & SER_RS485_RTS_ON_SEND)) >> + rs485conf->flags |= SER_RS485_RX_DURING_TX; >> + > > I wonder what should happen, if the device tree has both > > uart-has-rtscts; > rts-gpios = <...>; Hm, it seems that the code controls both in that case. > > . I think the right thing would be to check for > > sport->have_rtscts && !sport->have_rtsgpio I agree, since it controls both one can use the GPIO to have a working half duplex with low-active RTS configuration. Will send v3. -- Stefan