[Nouveau] Acer Aspire V7-582PG (Haswell, GTX 750M) fails to power off GPU via Power Resources

[Mika Westerberg]

On Thu, Oct 27, 2016 at 12:56:41AM +0200, Peter Wu wrote:
> Hi PCI/ACPI PM experts,
> 
> Since Linux 4.8, nouveau switched to rely on the PCIe port driver to
> transition to D3cold. This however does not happen for an Acer Aspire
> V7-582PG (Haswell, NVIDIA GTX 750M) from Rick.
> 
> Any idea why? acpidump, lspci, dmesg and other details can be found in
> the linked bug below.

> 
> Kind regards,
> Peter
> 
> On Wed, Oct 26, 2016 at 10:42:07PM +0000, bugzilla-daemon at freedesktop.org wrote:
> > https://bugs.freedesktop.org/show_bug.cgi?id=98398
> > 
> > --- Comment #11 from Peter Wu <peter at lekensteyn.nl> ---
> > So 4.7 and before used the "DSM" method on runtime-suspend:
> > - \_SB.PCI0.RP05.PEGP._DSM would be invoked to enable Optimus
> > - \_SB.PCI0.RP05.PEGP._PS3 is then invoked which would enter D3cold
> > (note, this method is still used in 4.8 on older laptops or with the
> > pcie_pm_port=off kernel option)
> > 
> > Since 4.8, _DSM is not called anymore by nouveau (when support from the PCI
> > core is detected) and this sequence should instead happen:
> > - \_SB.PCI0.RP05.PEGP._PS3 (does nothing besides updating _STA)
> > - PCIe core removes power for the PCIe port since all its children are in
> >   D3 and are willing to transition to D3cold. It does so by invoking
> >   \NVP3._OFF (where \NVP3 is the power resource from \_SB.PCI0.RP05._PR3)
> > 
> > That is how I think it should work in theory, but on Ricks laptop running
> > 4.8.4,
> > /sys/bus/devices/0000:1c.4/firmware_node/ does not have power_resources_D0
> > devices (which I do have on my own laptop for 0000:01:0).
> > 
> > The SSDT1 of Rick's Acer laptop shows this structure:
> > 
> >     If (\_OSI ("Windows 2013"))
> >     {
> >         Scope (\_SB.PCI0.RP05)
> >         {
> >         //...
> >             Name (_PR0, Package (0x01)  // _PR0: Power Resources for D0
> >             {
> >                 NVP3
> >             })
> >             Name (_PR2, Package (0x01)  // _PR2: Power Resources for D2
> >             {
> >                 NVP2
> >             })
> >             Name (_PR3, Package (0x01)  // _PR3: Power Resources for D3hot
> >             {
> >                 NVP3
> >             })
> >             // ...
> >             Method (_PS0, 0, NotSerialized)  // _PS0: Power State 0
> >             {
> >             }
> > 
> >             Method (_PS3, 0, NotSerialized)  // _PS3: Power State 3
> >             {
> >             }
> >         }
> > 
> >         Name (MSD3, Zero)
> >         PowerResource (NVP3, 0x00, 0x0000)
> >         {
> >             Name (_STA, One)  // _STA: Status
> >             // ...
> > 
> >             Method (_ON, 0, NotSerialized)  // _ON_: Power On
> >             {
> >                 // ...
> >             }
> > 
> >             Method (_OFF, 0, NotSerialized)  // _OFF: Power Off
> >             {
> >                 // ...
> >             }
> >         }
> > 
> > The dmesg does show "ACPI: Power Resource [NVP3] (on)", so I guess that the
> > methods are found. It is a mystery to me why the "power_resources_Dx" files are
> > not created, possibly breaking PM.

The ASL code looks right to me (except for the NVP2 which never set _STA
to 0 but should not affect here).

I wonder what does /sys/bus/pci/devices/0000:00:1c.4/firmware_node/path contain?