From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shawn Guo Subject: Re: [PATCH 15/15] arm: dts: imx: Add missing OPP properties for CPUs Date: Tue, 3 Jul 2018 15:12:16 +0800 Message-ID: <20180703071215.GM4348@dragon> References: <264124e14b966a1bbc07c364fbd89fc55aa765e6.1527244201.git.viresh.kumar@linaro.org> <1527248760.3472.6.camel@pengutronix.de> <20180528110739.ewmhlf72sl7u5ju7@vireshk-i7> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20180528110739.ewmhlf72sl7u5ju7@vireshk-i7> Sender: linux-kernel-owner@vger.kernel.org To: Viresh Kumar Cc: Lucas Stach , arm@kernel.org, Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , Rob Herring , Mark Rutland , devicetree@vger.kernel.org, Vincent Guittot , Daniel Lezcano , linux-kernel@vger.kernel.org, chris.redpath@arm.com, ionela.voinescu@arm.com, linux-arm-kernel@lists.infradead.org List-Id: devicetree@vger.kernel.org On Mon, May 28, 2018 at 04:37:39PM +0530, Viresh Kumar wrote: > Hi Lucas, > > On 25-05-18, 13:46, Lucas Stach wrote: > > This is a lot of duplicate information for what is effectively a shared > > cluster wide thing. This does absolutely not _feel_ right. > > I cannot agree more :) > > > What problem are you solving here? Why do we need all this duplicate > > information? Why can't we fix it by falling back to looking at cpu0 if > > needed? > > Let me try explaining one of the problem scenarios to you as your > platform is a single cluster one. Make cpufreq driver as module, don't > insert it, hotplug out CPU0 and now insert the cpufreq driver. The > cpufreq core will try adding the cpufreq policy for CPU1 but wouldn't > find the required information in the DT node of CPU1 and so will fail > or behave incorrectly. > > We can't look at CPU0 as we don't know they are related at all. > Nothing tells that to us. The right solution to fix the duplication is > to move to OPP-v2 bindings, which allow us to create a single OPP > table node and refer to it from all the CPU nodes. Because in case of > imx platforms getting updated here, we use the old and some platforms > specific frequency tables, we have to duplicate it everywhere. > > But looking from DT otherwise, all the device should anyway have all > the information required right in their node. That can be simplified > with things like phandle to opp-v2 node, but still everything needs to > be there. We shouldn't really rely on other CPU nodes to make it work. > That would be an incomplete definition of the hardware IMHO. Lucas, Are you fine with the patch now considering the respond from Viresh? Shawn