Hi Bastien, On Fri, Mar 04, 2016 at 04:12:27PM +0000, Bastien Nocera wrote: > Lukas Wunner <lukas <at> wunner.de> writes: > > Enable GPU switching on the pre-retina MacBook Pro (2008 - 2013), v5. > > I've tested your patchset on a MacBookPro8,1, with an integrated Intel and > discrete AMD/ATI GPUs. Hm, it must be either an 8,2 or 8,3. The 8,1 was a 13" machine and only had an integrated GPU. > I've used the COPR repository here to cut down on my compilation time: > https://copr.fedorainfracloud.org/coprs/firstyear/kernel-mbp/ > > I'm not certain how to test out your changes, or what the consequences should > be on a stock Fedora 23/GNOME 3.18 installation. After booting (note that I > did not change any command-line options in grub), a gnome-shell/gdm X11 > session comes up (I disabled Wayland, to rule out behavioural changes), I'd > log in to GNOME and gnome-shell (which starts another X11 session on > another VT). Switching and power control currently requires manual intervention by echoing commands to /sys/kernel/debug/vgaswitcheroo/switch as documented here: https://01.org/linuxgraphics/gfx-docs/drm/modes_of_use.html As you've correctly observed, the machine is initially switched to the discrete GPU and both GPUs are turned on. By echoing "IGD" to the sysfs file, you'll switch to the integrated GPU and turn off the discrete GPU. It's possible to let the EFI firmware switch to the integrated GPU on boot by using this tool: https://github.com/0xbb/gpu-switch However still both GPUs will be powered up, so you have to issue the "OFF" command to sysfs to power the discrete GPU down. Also, once you boot into OS X, the setting made by the gpu-switch tool will be overwritten and the machine will be switched to the discrete GPU again the next time you boot Linux. Note that switching is only possible from the text console, with X11/Wayland shut down. Obviously this is not great in terms of UX. A few years ago there was a GSoC proposal to get hot GPU switching to work on Linux (akin to what OS X does) but nothing ever came of it: http://www.phoronix.com/scan.php?page=news_item&px=OTIyMQ https://lists.x.org/archives/xorg/2011-March/052522.html Unfortunately this seems to be a low priority item for kernel graphics developers since nowadays most dual GPU notebooks no longer have a mux and cannot switch. The MacBook Pro seems to be the last one supporting this but I've witnessed a bit of an anti-Apple sentiment among kernel graphics developers since everything is non-standard there. Which is unfortunate because these machines have a large market share and Apple software quality is deteriorating rapidly so a lot of Mac users are ripe for converting to Linux. Anyway, one short-term improvement will be to add runtime pm support (called "Driver power control" in the vga_switcheroo documentation linked above). That way it'll no longer be necessary to power the discrete GPU up and down manually, this will happen automatically as needed (when switching or using render offloading with DRI PRIME). I have patches to enable this for radeon but they're completely untested: http://wunner.de/mbp_switcheroo_v5-4.5.tar.gz => gpu switching for 4.5 http://wunner.de/mbp_switcheroo_v5-4.5-runpm.tar.gz => runtime pm for radeon I have an Nvidia based machine and runtime pm doesn't work there yet because of bugs in nouveau that I haven't had the time to look into. > I did not use any external screens to test this. Since your machine has Thunderbolt, the external port is no longer switchable between GPUs, it can only be driven by the discrete GPU. So you need to power it up manually for this to work. You don't need to switch to it, but it's probably recommendable to save energy. (Otherwise both GPUs are on with the integrated GPU driving the panel and the discrete GPU driving the DP port.) The runpm tarball linked above contains a patch to automatically wake the discrete GPU on hotplug. I've heard that the AMD GPU is picky about external monitors and doesn't recognize them unless they're plugged in at exactly the right moment, so you may need to retry a couple of times until it works. Best regards, Lukas _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
