From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752724Ab1GSJJD (ORCPT ); Tue, 19 Jul 2011 05:09:03 -0400 Received: from eu1sys200aog112.obsmtp.com ([207.126.144.133]:51523 "EHLO eu1sys200aog112.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752456Ab1GSJJB (ORCPT ); Tue, 19 Jul 2011 05:09:01 -0400 Message-ID: <4E25499A.9070703@st.com> Date: Tue, 19 Jul 2011 14:38:42 +0530 From: viresh kumar User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.12) Gecko/20101027 Lightning/1.0b2 Thunderbird/3.1.6 MIME-Version: 1.0 To: "Koul, Vinod" Cc: "Williams, Dan J" , "linux-kernel@vger.kernel.org" , Shiraz HASHIM , Armando VISCONTI Subject: Re: [Query]: What should we do in txd->tx_submit() and device_issue_pending() References: <4E254067.1060408@st.com> <438BB0150E931F4B9CE701519A4463010871D6C2EF@bgsmsx502.gar.corp.intel.com> In-Reply-To: <438BB0150E931F4B9CE701519A4463010871D6C2EF@bgsmsx502.gar.corp.intel.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/19/2011 02:19 PM, Koul, Vinod wrote: > (pls wrap your email to 80lines, I have reflowed below for readability) >> Hi Dan/Vinod, >> >> I have one query regarding implementation of few routines in DMA drivers. >> >> What the exact purpose of txd->tx_submit() and device_issue_pending() routines? >> >> Should tx_submit() always start physical transfer (Obviously, if channel is >> free)? Or should it just queue requests and then finally a call to >> device_issue_pending() must start physical transfers? > (reflowed your email for 80lines) Sorry!! :( > tx_submit is not supposed to start the transfer, it is supposed to add the > descriptors in dma driver's queue. The issue_pending is supposed to actually > start the transfer. The reasons were well articulated is discussion we had > when we did the DMA documentation. > Pls see https://lkml.org/lkml/2011/5/24/530 > Thanks. -- viresh