From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753101Ab3AVHZ0 (ORCPT ); Tue, 22 Jan 2013 02:25:26 -0500 Received: from mga02.intel.com ([134.134.136.20]:35465 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751003Ab3AVHZZ convert rfc822-to-8bit (ORCPT ); Tue, 22 Jan 2013 02:25:25 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.84,512,1355126400"; d="scan'208";a="250574924" Message-ID: <1358839491.12502.41.camel@smile> Subject: Re: [PATCH 2/2] dw_dmac: return proper residue value From: Andy Shevchenko To: Vinod Koul Cc: Andy Shevchenko , Viresh Kumar , linux-kernel@vger.kernel.org, spear-devel Date: Tue, 22 Jan 2013 09:24:51 +0200 In-Reply-To: <20130121142205.GB26562@intel.com> References: <1358758844-24711-1-git-send-email-andriy.shevchenko@linux.intel.com> <1358758844-24711-2-git-send-email-andriy.shevchenko@linux.intel.com> <20130121084924.GA26562@intel.com> <1358761551.12502.39.camel@smile> <20130121142205.GB26562@intel.com> Organization: Intel Finland Oy Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT X-Mailer: Evolution 3.4.4-1 Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2013-01-21 at 06:22 -0800, Vinod Koul wrote: > On Mon, Jan 21, 2013 at 11:45:51AM +0200, Andy Shevchenko wrote: > > > > + return 0; > > > hmmm, why not use BLOCK_TS value. That way you dont need to look at direction > > > and along with burst can easily calculate residue... > > > > Do you mean to read CTL hi/lo and do > > > > desc->len - ctlhi.block_ts * ctllo.src_tr_width? > > > Yes > > I think it could be not precise when memory-to-peripheral transfer is > > going on. In that case you probably will have src_tr_width like 32 bits, > > meanwhile peripheral may receive only byte stream. > Nope that is not the case. > SAR/DAR is always incremented in src/dstn_tr_width granularity. For example if > you are using MEM to DMA, then SAR will always increment in case of x86 in 4byte > granularity as we will read bursts not singles. > > Also if check the spec, it says "Once the transfer starts, the read-back value is the > total number of data items already read from the source peripheral, regardless of > what is the flow controller" > > So basically you get what is read from buffer in case of MEM->PER and get what > is read from FIFO in case of PER->MEM which IMO gives you better or equal results > than your calulation. I will try this. Indeed I don't like usage of direction as well, and your solution seems much clear in that sense. -- Andy Shevchenko Intel Finland Oy