From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756830AbcBIPQ1 (ORCPT ); Tue, 9 Feb 2016 10:16:27 -0500 Received: from mga04.intel.com ([192.55.52.120]:57067 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754120AbcBIPQZ (ORCPT ); Tue, 9 Feb 2016 10:16:25 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.22,421,1449561600"; d="scan'208";a="899385835" Date: Tue, 9 Feb 2016 20:50:07 +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 the maximum requestor line Message-ID: <20160209152007.GQ19598@localhost> References: <1454941131-12308-1-git-send-email-robert.jarzmik@free.fr> <20160209033646.GK19598@localhost> <878u2u2vve.fsf@belgarion.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <878u2u2vve.fsf@belgarion.home> 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 Tue, Feb 09, 2016 at 08:20:05AM +0100, Robert Jarzmik wrote: > Vinod Koul writes: > > > On Mon, Feb 08, 2016 at 03:18:51PM +0100, Robert Jarzmik wrote: > >> The current number of requestor lines is limited to 31. This was an > >> error of a previous commit, as this number is platform dependent, and is > >> actually : > >> - for pxa25x: 40 requestor lines > >> - for pxa27x: 74 requestor lines > >> - for pxa3xx: 100 requestor lines > >> > >> As the driver doesn't need to know the exact number, but only an > > > > and why would that be a good assumption? > Well, the driver doesn't use the exact value. Would that be 128, 1000 or 10000, > it wouldn't change its behavior. The clients either pass -1UL (ie. no flow > control) or a requestor line number. Somehow that does not sound right to me. You seem to have no way of knowing what is the actual max request line for a platforms. What if on pxa25x user requests more than 40 lines? > > Btw shouldn't this data come from DT? > It can if you wish, but in this case I must amend the platform data case too, ie > mmp_dma_platdata. And this has an impact on MMP architecture. I'd rather have > the simpler approach unless you really want the exact number of requestor lines > to be passed in platform_data+DT. The information that you have X lines on a platform needs to be described and queried. I see current approach error prone -- ~Vinod