From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7FCF4C433DF for ; Thu, 21 May 2020 01:47:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6693720756 for ; Thu, 21 May 2020 01:47:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726925AbgEUBrJ (ORCPT ); Wed, 20 May 2020 21:47:09 -0400 Received: from mail.baikalelectronics.com ([87.245.175.226]:34352 "EHLO mail.baikalelectronics.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726840AbgEUBrJ (ORCPT ); Wed, 20 May 2020 21:47:09 -0400 Received: from localhost (unknown [127.0.0.1]) by mail.baikalelectronics.ru (Postfix) with ESMTP id A36508030776; Thu, 21 May 2020 01:47:06 +0000 (UTC) X-Virus-Scanned: amavisd-new at baikalelectronics.ru Received: from mail.baikalelectronics.ru ([127.0.0.1]) by localhost (mail.baikalelectronics.ru [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id L0UijymJus4x; Thu, 21 May 2020 04:47:06 +0300 (MSK) Date: Thu, 21 May 2020 04:47:05 +0300 From: Serge Semin To: Vinod Koul CC: Serge Semin , Andy Shevchenko , Viresh Kumar , Dan Williams , Alexey Malahov , Thomas Bogendoerfer , Paul Burton , Ralf Baechle , Arnd Bergmann , Rob Herring , , , , Subject: Re: [PATCH v2 5/6] dmaengine: dw: Introduce max burst length hw config Message-ID: <20200521014705.ha7mpxoio4gitjox@mobilestation> References: <20200306131048.ADBE18030797@mail.baikalelectronics.ru> <20200508105304.14065-1-Sergey.Semin@baikalelectronics.ru> <20200508105304.14065-6-Sergey.Semin@baikalelectronics.ru> <20200508114153.GK185537@smile.fi.intel.com> <20200512140820.ssjv6pl7busqqi3t@mobilestation> <20200512191208.GG185537@smile.fi.intel.com> <20200515063950.GI333670@vkoul-mobl> <20200517193818.jaiwgzgz7tutj4mk@mobilestation> <20200519170714.GT374218@vkoul-mobl.Dlink> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20200519170714.GT374218@vkoul-mobl.Dlink> X-ClientProxiedBy: MAIL.baikal.int (192.168.51.25) To mail (192.168.51.25) Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Tue, May 19, 2020 at 10:37:14PM +0530, Vinod Koul wrote: > On 17-05-20, 22:38, Serge Semin wrote: > > On Fri, May 15, 2020 at 12:09:50PM +0530, Vinod Koul wrote: > > > On 12-05-20, 22:12, Andy Shevchenko wrote: > > > > On Tue, May 12, 2020 at 05:08:20PM +0300, Serge Semin wrote: > > > > > On Fri, May 08, 2020 at 02:41:53PM +0300, Andy Shevchenko wrote: > > > > > > On Fri, May 08, 2020 at 01:53:03PM +0300, Serge Semin wrote: [nip] > > > > > > But let's see what we can do better. Since maximum is defined on the slave side > > > > > > device, it probably needs to define minimum as well, otherwise it's possible > > > > > > that some hardware can't cope underrun bursts. > > > > > > > > > > There is no need to define minimum if such limit doesn't exists except a > > > > > natural 1. Moreover it doesn't exist for all DMA controllers seeing noone has > > > > > added such capability into the generic DMA subsystem so far. > > > > > > > > There is a contract between provider and consumer about DMA resource. That's > > > > why both sides should participate in fulfilling it. Theoretically it may be a > > > > hardware that doesn't support minimum burst available in DMA by a reason. For > > > > such we would need minimum to be provided as well. > > > > > > Agreed and if required caps should be extended to tell consumer the > > > minimum values supported. > > > > Sorry, it's not required by our hardware. Is there any, which actually has such > > limitation? (minimum burst length) > > IIUC the idea is that you will tell maximum and minimum values supported > and client can pick the best value. Esp in case of slave transfers > things like burst, msize are governed by client capability and usage. So > exposing the set to pick from would make sense Agreed. I'll add min_burst capability. -Sergey > > -- > ~Vinod