hybrid-graphics-linux team mailing list archive

[Andreas Heider <andreas@xxxxxxxx>]

Hi everyone,

I'll just continue using this mailing list as a blog. After a lot of
wild guesses in all directions I now have a setup that could be a base
for useful graphics switching on Macbook Pros. It's not completely
reliable yet but hopefully that will improve in the future.

Switching between two running GPUs works pretty well and just needs a
bit more work. But that shouldn't be a big issue. 

The main problem I fought with is that after powering down the external
GPU the vbios vanishes and it's impossible to load the proprietary
nvidia driver:

[  214.505208] NVRM: failed to copy vbios to system memory.
[  214.507347] NVRM: RmInitAdapter failed! (0x30:0xffffffff:858)
[  214.507357] NVRM: rm_init_adapter(0) failed
 
The same problem exists with nouveau, after the first power cycle
nouveau doesn't load again if I unload it. I guess this is actually a
BIOS/EFI/firmware bug, since Apple's switching driver just keeps the
driver loaded.

So it's necessary to load the driver once and keep it loaded. This works
well with nouveau+vga_switcheroo but is a bit problematic with the
blob. 

At the moment I have the blob running with the patch from my first mail
and noticed that it survives a powercycle if X _is_ loaded while the GPU
is powered down. If I shutdown X I get this error when I try to start it
again afterwards:

[  144.390920] NVRM: RmInitAdapter failed! (0x26:0xffffffff:1170)
[  144.390930] NVRM: rm_init_adapter(0) failed

I'm not 100% certain that this really works but at the moment it's the
only possibility for getting full switching support with the blob.

Speaking of nvidia bugs, I also had problems with the blob not reliably
loading when I boot with EFI. 
Luckily it's possible to also enable the integrated card in BIOS
emulation mode. After staring a lot at the output of lspci -xxx from
both EFI and BIOS boot I noticed that this just requires flipping one
bit in the pci configuration space. This can be done by adding "setpci
-d 8086:0044 54.b=0b" in grub. This value will most likely only work for
this exact model, a MBP 6,2. For more information see
http://download.intel.com/design/processor/datashts/322813.pdf page 62.

If anyone has some hints how to better deal with the blob that would be
greatly appreciated. 

On Wed, 2012-02-29 at 10:33 +0100, Lekensteyn wrote:
> Hi Andreas,
> 
> I'm using nouveau + bbswitch (switcheroo also works, but not after
> resume), not on
> a mac, but a Clevo B7130 (branded as "BTO P-BOOK 17CL34").
> 
> The restoration of the PCI configuration space is a hack to allow the
> driver to load
> in case it was accidentally loaded while the card was off. This is
> especially necessary
> for the nvidia blob driver which loads itself if you try to
> access /dev/nvidia* devices.
> 
> In the case of switcheroo, no driver is attempted to be unloaded (see
> the second field
> of the switching_method struct and line 30 of src/switch/switching.c.

Sorry, that was my fault. I changed that for testing purposes and then
forgot about it.

> 
> gmux can be integrated into BB. Writing a new switcher module
> (src/switch/gmux.c)
> which also takes care of loading the switcheroo module (only if that
> is a safe operation!)
> should do the trick. Just be careful not to conflict with switcheroo.
> The other way is leave
> BB as it and require users to load gmux before BB.

Because of vbios situation and nouveau already working pretty well with
switcheroo I'd prefer to keep using that. 
> 
> Regards,
> Peter

Cheers,
Andreas

> 
> On Wed, Feb 29, 2012 at 12:25 AM, Andreas Heider <andreas@xxxxxxxx>
> wrote:
>         Hi Peter,
>         
>         I took another look at bumblebee today and got it running with
>         nouveau!
>         Bumblebee automatically powers the nvidia card down when it's
>         not in
>         use and starting programs with optirun works well.
>         
>         This required a dirty hack to bumblebee which you can find
>         here:
>         https://github.com/ah-/Bumblebee/commit/c5ab6f0e7f841045cee6905bb367c79091b0eb6b
>         
>         The problem is that bumblebee wants to save/restore the pci
>         configuration
>         space, which is already done by nouveau. (See
>         https://gist.github.com/1935992)
>         
>         It also shouldn't try to unload the driver.
>         
>         Do you think this could somehow be integrated into bumblebee?
>         
>         Cheers,
>         Andreas
>         
>         On Tue, 2012-02-28 at 16:14 +0100, Lekensteyn wrote:
>         > Hi Andreas,
>         >
>         > vga_switcheroo is a supported method since Bumblebee 3.0,
>         but I
>         > assumed that
>         > it would not be used for the nvidia driver. If you wish to
>         use the
>         > nvidia blob with
>         > switcheroo, you have to recompile Bumblebee and apply commit
>         > 85636d1f21b0644e7dd47e3931479860c55b7a05 (or use the develop
>         branch).
>         > The
>         > next version will have this change too.
>         >
>         > One shortcoming of vga_switcheroo now is that the state is
>         messed up
>         > after
>         > suspend: switcheroo remembered that the card was off, but in
>         reality
>         > the card
>         > is on. The module bbswitch worked around this by enabling
>         the card
>         > before
>         > suspend and disabling the card on resume.
>         >
>         > In some cases, while the card was turned off with switcheroo
>         caused
>         > the machine
>         > to lock when the card is tried to be accessed. If switcheroo
>         is not an
>         > option for
>         > Bumblebee, you can write your own switching code. See the
>         src/switch/
>         > directory
>         > for examples.
>         >
>         > Regards,
>         > Peter
>         > (Bumblebee and bbswitch developer)
>         >
>         > On Tue, Feb 28, 2012 at 3:16 PM, Andreas Heider
>         <andreas@xxxxxxxx>
>         > wrote:
>         >         Hello everybody,
>         >
>         >         I'm developing a vga_switcheroo driver for the Apple
>         Macbook
>         >         Pro models
>         >         with switchable graphics and have a few questions
>         about how to
>         >         integrate
>         >         it with the current linux hybrid graphics
>         infrastructure.
>         >
>         >
>         >         Apple implemented the switching using a "chip"
>         dubbed the
>         >         "gmux" (probably short for graphics multiplexer or
>         something
>         >         similar).
>         >         The gmux can power down the external graphics card,
>         switch the
>         >         DDC,
>         >         internal and external display connections
>         (individually)
>         >         between both
>         >         cards and set the backlight brightness. Unlike most
>         newer
>         >         laptops with
>         >         hybrid graphics, Apple's Macbook Pros use a physical
>         mux.
>         >
>         >         Luckily the gmux has remained mostly the same
>         between all
>         >         models with
>         >         switchable graphics, so it should be possible to
>         develop one
>         >         driver that
>         >         supports all of them.
>         >
>         >
>         >         This driver has actually been lying around in
>         unfinished state
>         >         for some
>         >         time now, until Seth Forshee from Canonical recently
>         rewrote
>         >         it into a
>         >         clean, backlight-only driver that will hopefully
>         find it's way
>         >         into
>         >         mainline soon.
>         >
>         >         My goal is to use Seth's work as a base and add the
>         other
>         >         features back
>         >         again and make it work well. A first version is
>         already
>         >         working and up
>         >         at https://github.com/ah-/gmux
>         >
>         >         This driver supports all vga_switcheroo operations
>         (discrete
>         >         power
>         >         on/off, display switching) and they all work on my
>         MBP 6,2
>         >         using the
>         >         intel and nouveau drivers.
>         >
>         >         But unfortunately, it doesn't work with bumbleebee
>         and/or the
>         >         proprietary
>         >         nvidia driver yet.
>         >
>         >
>         >         Because I'm using CUDA in other projects, getting
>         the
>         >         proprietary NVIDIA
>         >         driver running well is very interesting to me. The
>         setup
>         >         bumblebee plus
>         >         intel + nvidia_current without power management
>         works well on
>         >         my laptop
>         >         if I switch to the intel card in grub. (It's just
>         three
>         >         outbs). But that
>         >         breaks suspend and uses 10W more power than
>         necessary.
>         >
>         >         Does/should bumblebee work with a vga_switcheroo
>         driver just
>         >         for ON/OFF?
>         >
>         >         One thing I stumbled upon is a patch for the
>         proprietary
>         >         NVIDIA
>         >         driver originally written by "Kayo
>         <kayo@xxxxxxxxxxxx>" which
>         >         adds
>         >         some kind of vga_switcheroo support to it. I
>         modified it to
>         >         just register
>         >         with switcheroo (patch is attached), and that part
>         works well.
>         >         Turning
>         >         off the card works, but turning it on afterwards
>         doesn't. Any
>         >         Ideas?
>         >
>         >
>         >         Ultimately I'd like to get two scenarios/workflows
>         to work
>         >         well:
>         >
>         >         1. Real switching, by disabling one card completely
>         and only
>         >         using
>         >         the other one, requiring a logout/login.
>         >         Preferably using the NVIDIA driver.
>         >
>         >         2. Bumblebee switching with working power management
>         when the
>         >         NVIDIA
>         >         GPU is not in usw.
>         >
>         >
>         >         I'd appreciate any comments and thoughts on how to
>         implement
>         >         this and
>         >         how to integrate it with the current hybrid graphics
>         >         environment.
>         >
>         >         Cheers,
>         >         Andreas
>         >
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