Re: [PATCH 1/9] drm/nouveau: Don't leak runtime pm ref on driver unload

[Peter Wu <peter-VTkQYDcBqhK7DlmcbJSQ7g@public.gmane.org>]

On Tue, May 31, 2016 at 01:34:43PM +0200, Lukas Wunner wrote:
> On Mon, May 30, 2016 at 07:03:46PM +0200, Peter Wu wrote:
> > On Sun, May 29, 2016 at 05:50:06PM +0200, Lukas Wunner wrote:
> > > How exactly did you reach the situation where the root port didn't wake
> > > up when you tried to load nouveau again? (IRC conversation this week.)
> > 
> > Ensure that the pci/pm patches are applied, then:
> > 
> >  0. Unload nouveau (I have blacklisted it for testing).
> >  1. Enable rpm for the root port and children (control = auto).
> >  2. Verify in the kernel logs that the devices are sleeping:
> >         pcieport 0000:00:01.0: power state changed by ACPI to D3cold
> >  3. (Optional, to rule out issues with delays:) Disable rpm for the
> >     Nvidia device (control = on).
> >  4. modprobe nouveau.
> > 
> > The above test with v4.6 + 4 pci/pm patches (8b71f565) gives:
> > 
> >     50.245795 MXM: GUID detected in BIOS
> >     50.245948    nseval-0227 ns_evaluate           : **** Execute method [\_SB.PCI0.GFX0._DSM] at AML address ffffc90000013b11 length 492
> >     50.246016 ACPI Warning: \_SB.PCI0.GFX0._DSM: Argument #4 type mismatch - Found [Buffer], ACPI requires [Package] (20160108/nsarguments-95)
> >     50.246044    nseval-0227 ns_evaluate           : **** Execute method [\_SB.PCI0.GFX0._DSM] at AML address ffffc90000013b11 length 492
> >     50.246110    nseval-0227 ns_evaluate           : **** Execute method [\_SB.PCI0.PEG0.PEGP._DSM] at AML address ffffc90000018297 length 1F
> >     50.246256 ACPI Warning: \_SB.PCI0.PEG0.PEGP._DSM: Argument #4 type mismatch - Found [Buffer], ACPI requires [Package] (20160108/nsarguments-95)
> >     50.246289    nseval-0227 ns_evaluate           : **** Execute method [\_SB.PCI0.PEG0.PEGP._DSM] at AML address ffffc90000018297 length 1F
> >     50.246443 ACPI Warning: \_SB.PCI0.PEG0.PEGP._DSM: Argument #4 type mismatch - Found [Buffer], ACPI requires [Package] (20160108/nsarguments-95)
> >     50.246457    nseval-0227 ns_evaluate           : **** Execute method [\_SB.PCI0.PEG0.PEGP._DSM] at AML address ffffc90000018297 length 1F
> >     50.246932 pci 0000:01:00.0: optimus capabilities: enabled, status dynamic power, hda bios codec supported
> >     50.247005 VGA switcheroo: detected Optimus DSM method \_SB_.PCI0.PEG0.PEGP handle
> >     50.247084    nseval-0227 ns_evaluate           : **** Execute method [\_SB.PCI0.PEG0.PG00._ON] at AML address ffffc9000001086e length 11D
> >     50.390140 pcieport 0000:00:01.0: power state changed by ACPI to D0
> >     50.491893    nseval-0227 ns_evaluate           : **** Execute method [\_SB.PCI0.PEG0._DSW] at AML address ffffc90000010a2d length 1D
> >     50.492285 pcieport 0000:00:01.0: PME# disabled
> >     50.492583 nouveau 0000:01:00.0: unknown chipset (ffffffff)
> >     50.492687 nouveau: probe of 0000:01:00.0 failed with error -12
> 
> I've tested this on a MacBook Pro, which does not have ACPI _PR3
> methods for the root port to which the discrete GPU is attached.
> The port can thus only suspend to D3hot, not D3cold.
> 
> Even without patch [2/9], when unloading nouveau and letting the
> root port go to D3hot, the port is subsequently correctly resumed
> to D0 when reloading nouveau.
> 
> So the issue that you're seeing without patch [2/9] seems to be
> specific to Optimus/_PR3 machines. If possible you should try to
> get it working without patch [2/9] because that patch is really
> optional (as I've written in the commit message). I'm totally
> unfamiliar with Optimus but maybe lspci could help to debug this?

Without 2/9 I can prevent the issue by writing "on" to
/sys/bus/pci/devices/0000:00:01.0/power/control (the PCIe port), but
that effectively gives the same result as applying 2/9.

The problem occurs when the power is lost (by putting the PCIe port in
D3cold). Maybe it is a bug in the PCI core that does not re-initialize
devices under the port, but since a workaround is available (2/9), I
will focus on other issues first. Maybe it is worth to mention this
issue in the commit message for 2/9 though.
-- 
Kind regards,
Peter Wu
https://lekensteyn.nl
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