From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 0A6E125A for ; Mon, 20 Jul 2015 23:09:54 +0000 (UTC) Received: from mail-oi0-f54.google.com (mail-oi0-f54.google.com [209.85.218.54]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 5472922F for ; Mon, 20 Jul 2015 23:09:53 +0000 (UTC) Received: by oigd21 with SMTP id d21so76369252oig.1 for ; Mon, 20 Jul 2015 16:09:52 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <2015360.EW9BxZmMXF@vostro.rjw.lan> References: <1489458.8WDRattPkl@vostro.rjw.lan> <20150716155819.GA30423@kroah.com> <2015360.EW9BxZmMXF@vostro.rjw.lan> Date: Tue, 21 Jul 2015 01:09:52 +0200 Message-ID: From: Daniel Vetter To: "Rafael J. Wysocki" Content-Type: text/plain; charset=UTF-8 Cc: "Brown, Len" , "ksummit-discuss@lists.linuxfoundation.org" , Alan Stern , Kristen Carlson Accardi , Grant Likely Subject: Re: [Ksummit-discuss] [TECH TOPIC] System-wide interface to specify the level of PM tuning List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, Jul 21, 2015 at 12:21 AM, Rafael J. Wysocki wrote: > On Friday, July 17, 2015 01:41:56 PM Daniel Vetter wrote: >> On Thu, Jul 16, 2015 at 5:58 PM, Greg KH wrote: >> > On Thu, Jul 16, 2015 at 08:53:02AM -0700, Josh Triplett wrote: >> >> But the kernel already has quirk tables for various hardware, and that >> >> seems appropriate to continue putting in the kernel. >> > >> > For some types of devices, sure. For others, like broken USB keyboards >> > that can't handle autosuspend, no. For those we need a userspace >> > _whitelist_ that udev can use. So there's no one answer that works for >> > all types of quirks. >> >> Whether white or blacklist or some other mixed thing doesn't really >> matter. Imo the important part is that driver maintainers are in the >> best position to maintain that, and pushing it out to anyone else is >> just really not doing our jobs. And I think for most of these quirk >> lists the kernel does seem like the most appropriate place. If the >> list becomes giantic then we can move it to userspace (if that's >> really a problem, afaik no one proposed yet to move device match >> tables into userspace either and that's kinda the same thing really). >> But as long as there's no white/black/whatever list yet starting in >> the kernel is imo the right place. > > Well, I'm wondering, then, why i915.enable_psr is not enabled by default, > for one example? > > Failing to enable it prevents some SoCs from using the deepest available > C-states which in turn hurts battery life of the systems containing them > quite a bit, so there surely is a reason to have it enabled. Because it's broken on a lot of machines, and it takes a pile of effort to fix it. That work is under way now, but for a long time priorities set by management where much more set on chasing the next shiny thing. Took a few years of making noises about dropping it all if it doesn't get fixed. This is actually a perfect example of what I mean with "hey it works on my machine here, but I can't be bothered to fix up the corner-cases so let's keep it disabled and move on". And the corner cases are hung machines and frozen displays (and a few other things), and we inflicted that a few times on Linus even. Cheers, Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch