From mboxrd@z Thu Jan 1 00:00:00 1970 From: Will Deacon Subject: Re: [PATCH V3 0/5] iommu/arm-smmu: Add runtime pm/sleep support Date: Mon, 3 Apr 2017 18:23:07 +0100 Message-ID: <20170403172307.GI5706@arm.com> References: <1489073748-3659-1-git-send-email-sricharan@codeaurora.org> <20170331175457.GD4897@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-arm-msm-owner@vger.kernel.org To: Rob Clark Cc: Sricharan R , Mark Rutland , "devicetree@vger.kernel.org" , Mathieu Poirier , linux-arm-msm , Stephen Boyd , "iommu@lists.linux-foundation.org" , Rob Herring , linux-clk@vger.kernel.org, "linux-arm-kernel@lists.infradead.org" List-Id: devicetree@vger.kernel.org On Fri, Mar 31, 2017 at 10:58:16PM -0400, Rob Clark wrote: > On Fri, Mar 31, 2017 at 1:54 PM, Will Deacon wrote: > > On Thu, Mar 09, 2017 at 09:05:43PM +0530, Sricharan R wrote: > >> This series provides the support for turning on the arm-smmu's > >> clocks/power domains using runtime pm. This is done using the > >> recently introduced device links patches, which lets the symmu's > >> runtime to follow the master's runtime pm, so the smmu remains > >> powered only when the masters use it. > > > > Do you have any numbers for the power savings you achieve with this? > > How often do we actually manage to stop the SMMU clocks on an SoC with > > a handful of masters? > > > > In other words, is this too coarse-grained to be useful, or is it common > > that all the devices upstream of the SMMU are suspended? > > well, if you think about a phone/tablet with a command mode panel, > pretty much all devices will be suspended most of the time ;-) Well, that's really what I was asking about. I assumed that periodic modem/radio transactions would keep the SMMU clocked, so would like to get a rough idea of the power savings achieved with this coarse-grained approach. Will