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=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,T_DKIMWL_WL_HIGH,USER_AGENT_MUTT autolearn=ham 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 D5509C6778C for ; Fri, 6 Jul 2018 06:00:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7EF3520896 for ; Fri, 6 Jul 2018 06:00:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="cRAo2+qN" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7EF3520896 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934339AbeGFGAs (ORCPT ); Fri, 6 Jul 2018 02:00:48 -0400 Received: from mail.kernel.org ([198.145.29.99]:40612 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932684AbeGFGAp (ORCPT ); Fri, 6 Jul 2018 02:00:45 -0400 Received: from localhost (unknown [223.226.33.155]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 3572E21468; Fri, 6 Jul 2018 06:00:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1530856844; bh=K3k5KRAN80Th2LaMV0QfGJGKj0muzPc/rm+5xxmXMv4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=cRAo2+qNbtXJ8koJwet5bV1avI6unUBPD263YJ5xK8tUgQYbacXNGYOH9KnGS+dfW /r8GRSL33d+nN37kYGuMiHATzG4V6O8DtNcJjclLLDqx8SNoo7FqQq82u2Hi8bT48/ rBEVyAw0Bee/033Fz0F4/Evb1SnStW9fQcMFprLQ= Date: Fri, 6 Jul 2018 11:30:36 +0530 From: Vinod To: Andy Shevchenko Cc: Marek Szyprowski , Mark Brown , Lars-Peter Clausen , dmaengine , ALSA Development Mailing List , Linux Kernel Mailing List , Dan Williams , Bartlomiej Zolnierkiewicz Subject: Re: [PATCH] dma: add support for reporting pause and resume separately Message-ID: <20180706060036.GR22377@vkoul-mobl> References: <20180702130819eucas1p2e11d8fabec93ba78d9e84f4ca6e5fd65~9jzNWZMqQ1216712167eucas1p27@eucas1p2.samsung.com> <20180704070033.GA22377@vkoul-mobl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04-07-18, 13:38, Andy Shevchenko wrote: > On Wed, Jul 4, 2018 at 10:00 AM, Vinod wrote: > > Hi Marek, > > > > On 02-07-18, 15:08, Marek Szyprowski wrote: > >> 'cmd_pause' DMA channel capability means that respective DMA engine > >> supports both pausing and resuming given DMA channel. However, in some > >> cases it is important to know if DMA channel can be paused without the > >> need to resume it. This is a typical requirement for proper residue > >> reading on transfer timeout in UART drivers. There are also some DMA > >> engines with limited hardware, which doesn't really support resuming. > > > > Am curious given that your hardware does not support resume, what was motivation > > for adding pause? > > > >> Reporting pause and resume capabilities separately allows UART drivers to > >> properly check for the really required capabilities and operate in DMA > >> mode also in systems with limited DMA hardware. On the other hand drivers, > >> which rely on full channel suspend/resume support, should now check for > >> both 'pause' and 'resume' features. > >> > >> Existing clients of dma_get_slave_caps() have been checked and the only > >> driver which rely on proper channel resuming is soc-generic-dmaengine-pcm > >> driver, which has been updated to check the newly added capability. > >> Existing 'cmd_pause' now only indicates that DMA engine support pausing > >> given DMA channel. > > > > The change looks fine to me. I was hoping that serial would also check > > this.. > > AFAIU serial does not need to resume. I meant the serial should check for Pause capability.. -- ~Vinod