From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Warren Subject: Re: [PATCH] dma: tegra: implement suspend/resume callbacks Date: Thu, 02 May 2013 12:42:30 -0600 Message-ID: <5182B396.308@wwwdotorg.org> References: <1366797267-29567-1-git-send-email-ldewangan@nvidia.com> <20130430103046.GD1960@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20130430103046.GD1960-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org> Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Vinod Koul Cc: Laxman Dewangan , djbw-b10kYP2dOMg@public.gmane.org, linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-tegra@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.