Re: PCI: Revert "PCI: Add runtime PM support for PCIe ports"

[Mika Westerberg <mika.westerberg@linux.intel.com>]

On Mon, Jan 02, 2017 at 02:10:19PM +0200, Mika Westerberg wrote:
> I've checked the acpidump of this machine and it does not seem to be a
> traditional Optimus machine. At least this one is missing the magic _DSM
> which is used to gather capabilities of the graphics device.
> 
> However, it does have _PR3 and it is attached to the device
> (_SB.PCI0.PEG) itself, not the root port.
> 
> One thing you could try in addition to Lucas' patches is just to prevent
> D3cold from the device by doing this:
> 
>   # echo 0 > /sys/bus/pci/devices/0000:01:00.0/d3cold_allowed

Following messages look like the device fails to resume properly from D3cold:

Dec 30 08:45:06 klaptop kernel: [   27.775949] nouveau 0000:01:00.0: rpm_resume
Dec 30 08:45:06 klaptop kernel: [   27.776316] nouveau 0000:01:00.0: Refused to change power state, currently in D3
Dec 30 08:45:06 klaptop kernel: [   27.836049] nouveau 0000:01:00.0: Refused to change power state, currently in D3
Dec 30 08:45:06 klaptop kernel: [   27.836053] nouveau 0000:01:00.0: Refused to change power state, currently in D3

This happens if we read back 0xffffffff from PM register.

Dec 30 08:45:06 klaptop kernel: [   27.836055] nouveau 0000:01:00.0: DRM: resuming kernel object tree...
Dec 30 08:45:06 klaptop kernel: [   27.836127] nouveau 0000:01:00.0: pci: failed to adjust cap speed
Dec 30 08:45:06 klaptop kernel: [   27.836131] nouveau 0000:01:00.0: pci: failed to adjust lnkctl speed

Preventing D3cold should at least show some difference on resume path.