From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: [PATCH 1/2] vga_switcheroo: add power support for windows 10 machines. Date: Mon, 14 Mar 2016 13:50:41 +0100 Message-ID: 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> <20160314102357.GA1793@lahna.fi.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: Received: from mail-lb0-f195.google.com ([209.85.217.195]:33930 "EHLO mail-lb0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752444AbcCNMun (ORCPT ); Mon, 14 Mar 2016 08:50:43 -0400 In-Reply-To: <20160314102357.GA1793@lahna.fi.intel.com> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Mika Westerberg Cc: Dave Airlie , "Rafael J. Wysocki" , "Rafael J. Wysocki" , dri-devel , "linux-pm@vger.kernel.org" , ACPI Devel Maling List , Linux PCI , Linux Kernel Mailing List On Mon, Mar 14, 2016 at 11:23 AM, Mika Westerberg wrote: > 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? We can do that to start with. If there are no problems in the field with it, I don't see any problems in principle. > 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). Sounds reasonable. >> 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. That would be fine by me. Thanks, Rafael