Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754650AbdFWJgz (ORCPT ); Fri, 23 Jun 2017 05:36:55 -0400 Received: from mail2.eckelmann.de ([217.19.183.90]:59713 "EHLO mail2.eckelmann.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754233AbdFWJgw (ORCPT ); Fri, 23 Jun 2017 05:36:52 -0400 X-Greylist: delayed 629 seconds by postgrey-1.27 at vger.kernel.org; Fri, 23 Jun 2017 05:36:52 EDT From: "Schenk, Gavin" To: Clemens Gruber , "linux-serial@vger.kernel.org" CC: Greg Kroah-Hartman , "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" , "u.kleine-koenig@pengutronix.de" , "Fabio Estevam" Subject: AW: [Customers.Eckelmann] [PATCH] serial: imx: disable DMA for RS-485 on i.MX6 SMP Thread-Topic: [Customers.Eckelmann] [PATCH] serial: imx: disable DMA for RS-485 on i.MX6 SMP Thread-Index: AQHS6/hH3cjXeY/a5061iWkjqC7WMqIyJIkw Date: Fri, 23 Jun 2017 09:26:14 +0000 Message-ID: References: <20170620153701.12626-1-clemens.gruber@pqgruber.com> In-Reply-To: <20170620153701.12626-1-clemens.gruber@pqgruber.com> Accept-Language: de-DE, en-US Content-Language: de-DE X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [2a00:1f08:4007:1c00:292d:4e5a:1f2d:984b] Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by mail.home.local id v5N9bAQX028445 Content-Length: 1380 Lines: 32 Hi, > > DMA support for half-duplex RS-485 never worked correctly on i.MX6Q/D > due to an undiscovered SMP-related bug, instead of the real data being > sent out, the rest of the transmit buffer is sent (xmit->tail jumps over > xmit->head in imx_transmit_buffer and UART_XMIT_SIZE bytes are sent out) > More details: https://lkml.org/lkml/2017/1/4/579 > We see exactly this issue on our platform, based on i.MX6dl. We use the RS485 mode to implement a Modbus interface. We have another platform based on i.MX25 running the same Linux 4.9.30 code that is not affected! > Disable it for that configuration until the bug is found and fixed. > > We need to know at probe time if we can enable DMA. (RS-485 could be > enabled after that). Let's therefore only enable DMA if it is not an > i.MX6Q/D UART with uart-has-rtscts in the DT and CONFIG_SMP enabled. > Uwe Kleine-König had the idea to disable DMA on the i.MX6dl based platform via dts and this is our current workaround. Regards Gavin Schenk Eckelmann AG Vorstand: Dipl.-Ing. Peter Frankenbach (Sprecher) Dipl.-Wi.-Ing. Philipp Eckelmann Dr.-Ing. Marco Münchhof Dr.-Ing. Frank Uhlemann Vorsitzender des Aufsichtsrats: Hubertus G. Krossa Stv. Vorsitzender des Aufsichtsrats: Dr.-Ing. Gerd Eckelmann Sitz der Gesellschaft: Berliner Str. 161, 65205 Wiesbaden, Amtsgericht Wiesbaden HRB 12636 http://www.eckelmann.de