Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934072AbcCNKYJ (ORCPT ); Mon, 14 Mar 2016 06:24:09 -0400 Received: from mga04.intel.com ([192.55.52.120]:34514 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750932AbcCNKYD (ORCPT ); Mon, 14 Mar 2016 06:24:03 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.24,335,1455004800"; d="scan'208";a="65881325" Date: Mon, 14 Mar 2016 12:23:57 +0200 From: Mika Westerberg To: Dave Airlie Cc: "Rafael J. Wysocki" , "Rafael J. Wysocki" , dri-devel , "linux-pm@vger.kernel.org" , ACPI Devel Maling List , Linux PCI , Linux Kernel Mailing List Subject: Re: [PATCH 1/2] vga_switcheroo: add power support for windows 10 machines. Message-ID: <20160314102357.GA1793@lahna.fi.intel.com> References: <1457504045-12738-1-git-send-email-airlied@gmail.com> <2736217.utxPzJExd5@vostro.rjw.lan> <20160311105815.GS1796@lahna.fi.intel.com> <2759763.dR5D0KopkA@vostro.rjw.lan> <20160314094335.GE1796@lahna.fi.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1714 Lines: 44 On Mon, Mar 14, 2016 at 07:47:39PM +1000, Dave Airlie wrote: > > > >> - if (pcie_port_runtime_suspend_allowed(dev)) > >> + if (pcie_port_runtime_suspend_allowed(dev)) { > >> + pm_runtime_allow(&dev->dev); > > > > PCI drivers typically have left this decision up to the userspace. I'm > > wondering whether it is good idea to deviate from that here? Of course > > this allows immediate power savings but could potentially cause problems > > as well. > > > > No distro has ever shipped userspace to do this, I really think this > is a bad design. > We have wasted countless watts of power on this stupid idea that people will > run powertop, only a few people in the world run powertop, lots of > people use Linux. That is a fair point. I do not have anything against calling pm_runtime_allow() here. In fact we already do the same in Intel LPSS drivers. I just wanted to bring that up. Rafael, what do you think? If we anyway are going to add cut-off date to enable runtime PM we should expect that the hardware is also capable of doing so (and if not we can always blacklist the exceptions). > The kernel should power stuff down not wait for the user to run powertop, > At least for the GPU it's in the area of 8W of power, and I've got the > GPU drivers doing this themselves, > > I could have the GPU driver call runtime allow for it's host bridge I suppose, > if we insist on the userspace cares, but I'd prefer not doing so. > > > I think we need to add corresponding call to pm_runtime_forbid() in > > pcie_portdrv_remove(). > > Yes most likely. BTW, I can add both calls to the next version of PCIe runtime PM patches if you are OK with that, and all agree this is a good idea.