From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761086Ab3EBSme (ORCPT ); Thu, 2 May 2013 14:42:34 -0400 Received: from avon.wwwdotorg.org ([70.85.31.133]:40967 "EHLO avon.wwwdotorg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760697Ab3EBSmd (ORCPT ); Thu, 2 May 2013 14:42:33 -0400 Message-ID: <5182B396.308@wwwdotorg.org> Date: Thu, 02 May 2013 12:42:30 -0600 From: Stephen Warren User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130106 Thunderbird/17.0.2 MIME-Version: 1.0 To: Vinod Koul CC: Laxman Dewangan , djbw@fb.com, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] dma: tegra: implement suspend/resume callbacks References: <1366797267-29567-1-git-send-email-ldewangan@nvidia.com> <20130430103046.GD1960@intel.com> In-Reply-To: <20130430103046.GD1960@intel.com> X-Enigmail-Version: 1.4.6 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 04/30/2013 04:30 AM, Vinod Koul wrote: > On Wed, Apr 24, 2013 at 03:24:27PM +0530, Laxman Dewangan wrote: >> Implement suspend/resume callbacks to store APB DMA channel's >> register on suspend and restore APB DMA channel's register on >> resume. ... > You dont seem to handle suspend when DMA is active? Otherwise looks fine. > Stephen, you okay with this patch? Yes, I think this looks fine. Sorry for the slow response; I was on vacation. One question though: Laxman mentioned that DMA clients were responsible for suspending their DMA accesses themselves. Does the dmaengine core define the semantics here; are DMA drivers supposed to handle suspend with active DMAs, or should DMA clients suspend their DMA accesses themselves as Laxman suggests? If the latter, I wonder if we actually need to save/restore all the registers, since after resume, a new DMA access would be started in all cases, which would then reprogram the HW.