Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752790AbbDMHkY (ORCPT ); Mon, 13 Apr 2015 03:40:24 -0400 Received: from relay1.mentorg.com ([192.94.38.131]:58237 "EHLO relay1.mentorg.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751787AbbDMHkS (ORCPT ); Mon, 13 Apr 2015 03:40:18 -0400 Message-ID: <552B72DF.7060006@mentor.com> Date: Mon, 13 Apr 2015 16:40:15 +0900 From: jiwang User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: Sebastian Andrzej Siewior CC: , , , , , Subject: Re: [PATCH v1 11/15] serial: imx: initialized DMA w/o HW flow enabled References: <1418116296-12082-1-git-send-email-jiada_wang@mentor.com> <1418116296-12082-12-git-send-email-jiada_wang@mentor.com> <20150409120057.GA12596@breakpoint.cc> In-Reply-To: <20150409120057.GA12596@breakpoint.cc> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1641 Lines: 37 Hi Sebastian On 04/09/2015 09:00 PM, Sebastian Andrzej Siewior wrote: > On 2014-12-09 18:11:32 [+0900], Jiada Wang wrote: >> From: Anton Bondarenko >> >> DMA mode for UART can be used even w/o HW flow control with RTS/CTS. >> So it need to be initialized and enabled earlier. >> >> Signed-off-by: Anton Bondarenko >> Signed-off-by: Jiada Wang > How was this tested? I read you used the Sambe IMX6Q. I have here the > Wandboard which is IMX6D and a PBAB01 which is IMX6Q. Both have the same > issue with this patch, that is once DMA is enabled I receive the data in > question plus one extra byte which is 0x00. > That extra byte was not part of transaction. After that, the SDMA driver > is handling interrupts like crazing and feeding one byte data (usually > 0x00 but sometimes 0x02 not sure if this new or whatever was there > before) to the core. Those one byte transaction are bogus of course. > > My question is how was this tested. Before your patch none of my boards > were using DMA because RTS/CTS is not in use and this was a key > requirement. Now SDMA goes crazy. Is there a SDMA firmware required for > this to work? We tested the patch set with our modified kernel tree, and I find upstream kernel is not building SDMA firmware, I will submit another patch to add it. Thanks, Jiada > Sebastian -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/