Hello. Currently I'm using Slackware-current with 4.1.15-generic-smp kernel on my Acer 5560G laptop. It has hybrid AMD graphics: A8-3500M APU and HD 6740G2 graphics.

There are two options in BIOS: switchable graphics and integrated graphics. I can load Slackware with integrated graphics only. If switchable graphics enabled in BIOS, loading of Slackware freezes at "Mounting non-root local filesystems" stage.

Tried to Google it, but didn't find any solutions. Also tried to load Arch installation CD - same problem occurred.

I tried different kernels, like huge and no-smp. No luck. I didn't try proprietary drivers yet. I'd like to make it work without it.

Did anybody experienced this before? Any ideas?

Can this provide some input?

https://bbs.archlinux.org/viewtopic.php?id=57084&p=277
https://bbs.archlinux.org/viewtopic.php?id=122728
https://help.ubuntu.com/community/HybridGraphics

It provides a way to disable dedicated graphics on boot and enable it later from console when needed, but it's not really solves the problem. So it's manual switching of graphics. But I want automatic.

Also, it says, that Intel and Nvidia have better ways of dealing with hybrid graphics.

Maybe, I should just try proprietary drivers... Or find myself another notebook

Hallo, I have a similar laptop (Dell 5555) with A10-7800P and an additional radeon R5 M335 (Dell says it's 345DX ...). I think the problem is that the newer 4.1.15 kernel does not support these graphics card configuration properly yet, iirc properly support for these are coming from kernel 4.2. I think the problem is that the display is connected only to the integrated graphics card. But when you boot it with the external gpu, it tries to initialize the external gpu's display, which does not exist. The integrated gpu has to be initialized and working for passing through the other card's framebuffer.

I could boot it by passing the kernel parameters " nomodeset amd_iommu=0 " in BIOS mode and with "amd_iommu=0" in UEFI mode. I booted kernel 4.3.3 with it the same way. I don't know if your case needs amd_iommu=0. Also you can try amd_iommu_v2=0. On the other hand, amd_iommu_v2 is loaded by fglrx here. I use kernel 4.1.15 on slackware 14.1 with the amd 15.12 proprietary driver, since I need 3d acceleration. I also tried slackware-current using alienbob's live dvd and it worked the same way. Actually, with the new eudev it seems to be properly recognized and I can startx with KDE. 2d is working great but, I didn't get 3d acceleration with the opensource driver on this machine. That's expected for my case, since the gpus I have here are not properly supported with kernel 4.1.15 and xorg needs newest amdgpu driver to work. I will try again getting the opensource driver working, so I'll keep an eye and post here if someone else hasn't found a solution yet. Maybe you need to tell it somehow to use the integrated adapter when you boot it.

** The rest of the post is not exactly related to your case, since you ask about opensource drivers, but maybe it's helpful.

The laptop seems to work fine with the proprietary driver, I can select which gpu to use from the amd control panel. Actually having used amd's driver in the past and had mixed feelings about it, this 15.12 driver seems to work ok. I can game better than the old radeon hd2600 i used in the past, my 3d-related code works, even 2d is more acceptable. Moreover, I tested 15.12's aticonfig utility, and it says that I can enable a crossfire mode (Multiple GPU chain it calls it).
I could do the following (adapter 0 is the integrated one , adapter 1 is the external one)
It says to restart to set these and the tool says it's has crossfire (Muliple GPU chain) enabled, but whether this works or not and how well, I don't know yet. Finally you can reset these all back by using

Just tried 4.3.3 kernel first with amdgpu driver and then with default radeon driver. My graphics card is not supported by Amdgpu. And 4.3.3 kernel with radeon driver still freezes on startup. Several seconds after initialization of dedicated graphics.

"nomodset amd_iommu_v2=0" prevents initialization of graphics. System loads with "switchable" set in BIOS, but with VESA drivers only. Not what I needed.

I would say that AMD APU and AMD dedicated card usually works best.
I got AMD A10-5750M (Richland) with Radeon HD 8650G/8670M Dual GPU and it works great and i only use DRI_PRIME=1 to use the dedicated GPU.
Looking at the posted links it's for Intel/AMD systems and uses vgaswitcheroo you don't use that on an AMD/AMD.
In an AMD/AMD system using DRI2 you need to xrandr --listproviders to see your cards and then set them up xrandr --setprovideroffloadsink after that DRI_PRIME will work, with DRI3 DRI_PRIME should just work and you don't need to set provideroffloadsink.
Your APU (Llano) and GPU is from 2011 so the support should be there for you as well out of the box.
You need to use the open source driver in current for that hardware i use it for my hw and it works real good.
It might be that you ran into a bug.
My personal experience is that an AMD/AMD setup works much better then Intel/Nvidia or Intel/AMD and should have less problems (doesn't help in your case).

That it doesn't boot makes me think it's something with acpi so i would play around with different acpi options and also check bios updates changelog if there's an newer bios that seems to fix any related bugs.
Edit: i use depending of how you like to type it.
But since you hw is older then mine you may also try 2006 instead of 2012.

Thanks, I'll try that. There are two BIOS version for my laptop. I tried both. No luck.

Just tried to add "acpi=off" to kernel parameters. When graphics mode set in BIOS as "integrated", system loads without problem and with disabled acpi. When graphics mode set in BIOS as "switchable", system goes into kernel panic before even initrd.gz loaded.

Did a little reading about Linux and Acer 5560g laptop. It seems, that it's dedicated graphics card won't work with opensource drivers. Here is a thread on kernel bug tracker from year and a half ago: https://bugzilla.kernel.org/show_bug.cgi?id=74551

So, here is another problem: I can't run proprietary drivers (AMD Catalyst 15.9 for x86_64). I installed patched 15.9 on 4.1.15 kernel without errors. But With enabled ACPI I see "GAL initialization failure" and black screen. And with "acpi=off", passed to kernel, I see same black screen and message like "PCI device is not VGA" or something like that. I tried several other kernel parameters, like "pci=nocsr" and "acpi_osi", but it didn't work.

Reading that bug report it seems that that old card might be mux (multiplexer) and might need vgaswitcheroo after all but i'm not sure.
I would post to that bug or open a new one (and link to the old bug) since you are now supposed to use the open driver, the hardware doesn't seem to be the same but close.

Did you report to that bug or opened a new one?
A bug won't magically solve itself.