From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754829AbcHSG1h (ORCPT ); Fri, 19 Aug 2016 02:27:37 -0400 Received: from mga04.intel.com ([192.55.52.120]:1986 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752938AbcHSG1g (ORCPT ); Fri, 19 Aug 2016 02:27:36 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.28,544,1464678000"; d="scan'208";a="868075379" Date: Fri, 19 Aug 2016 12:02:24 +0530 From: Vinod Koul To: Robert Jarzmik Cc: Daniel Mack , Haojian Zhuang , linux-arm-kernel@lists.infradead.org, dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] dmaengine: pxa_dma: fix hotchain corner case Message-ID: <20160819063224.GU9681@localhost> References: <1470596509-1726-1-git-send-email-robert.jarzmik@free.fr> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1470596509-1726-1-git-send-email-robert.jarzmik@free.fr> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Aug 07, 2016 at 09:01:48PM +0200, Robert Jarzmik wrote: > In the case where a descriptor is chained on a running channel, and as > explained in the comment in the code 10 lines above, the success of the > chaining is ensured either if : > - the DMA is still running > - or if the chained transfer is completed > > Unfortunately the transfer completness test was done on the descriptor > to which the transfer was chained, and not the transfer being chained at > the end, ie. hot-chained. > > This corner case is extremely hard to trigger, as usually the DMA chain > is still running, and the first case takes care of returning success of > the hot-chaining. It was seen by hot-chaining several "small transfers" > to a running "big transfer", not in a real-life usecase but by testing > the robustness of the driver. Applied, thanks -- ~Vinod