From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lukas Wunner Subject: Re: Backlight control does not work on an Apple dual-GPU (intel/nvidia) system using nouveau Date: Sun, 14 Feb 2016 14:40:45 +0100 Message-ID: <20160214134045.GA16892@wunner.de> References: <56BF996F.3030503@guruburu.com> <20160213233912.GA16687@wunner.de> <20160214053827.GA25439@srcf.ucam.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mailout2.hostsharing.net ([83.223.90.233]:57145 "EHLO mailout2.hostsharing.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751452AbcBNNkR (ORCPT ); Sun, 14 Feb 2016 08:40:17 -0500 Content-Disposition: inline In-Reply-To: Sender: platform-driver-x86-owner@vger.kernel.org List-ID: To: Michael Marineau Cc: Matthew Garrett , Bruno =?iso-8859-1?Q?Pr=E9mont?= , Gaele Strootman , Bjorn Helgaas , Bruno Bierbaumer , platform-driver-x86@vger.kernel.org, Darren Hart Hi Michael, On Sat, Feb 13, 2016 at 10:36:47PM -0800, Michael Marineau wrote: > On Feb 13, 2016 9:38 PM, "Matthew Garrett" wrote: > > > > On Sun, Feb 14, 2016 at 12:39:12AM +0100, Lukas Wunner wrote: > > > @Bjorn Helgaas: Do you think this masquerade patch would be eligible > > > for inclusion in the kernel or is this not in your department? > > > https://www.marc.info/?l=grub-deavel&m=141586614924917&w=2 > > > > I think this is an entirely appropriate piece of code to add to the EFI > > boot code in the kernel. > > One note on that code: making the Intel card visible exposes a number of > other bugs such as power management with nouveau not working any more and > despite vga switcheroo becoming available it isn't possible to switch to > the Intel gpu because, at least on my machine, neither the Intel nor > nouveau drivers can figure out how to bring up the eDP link or some such. That is correct. GPU switching for pre-retinas was finally queued for 4.6 this week, retinas are my next target. To overcome the link training issues I had experimented with AUX proxying last year until I realized in December that the DP spec has a link training exemption for eDP. Basically what we need to do is wait until the active GPU has set up its eDP output, then communicate voltage swing, pre-emphasis, lane count etc to the inactive GPU's driver (via vga_switcheroo) and use these pre-calibrated values to set up the output. I've hacked together an initial implementation of the i915 and vga_switcheroo side of things in early January, then got side-tracked while working on the nouveau part. However I'll get back to this pretty soon. Best regards, Lukas