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Date: Mon, 2 Jan 2017 15:53:39 +0200
From: Mika Westerberg <mika.westerberg@linux.intel.com>
To: Lukas Wunner <lukas@wunner.de>
Cc: Kilian Singer <kilian.singer@quantumtechnology.info>,
	Bjorn Helgaas <helgaas@kernel.org>,
	linux-pci <linux-pci@vger.kernel.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Subject: Re: PCI: Revert "PCI: Add runtime PM support for PCIe ports"
Message-ID: <20170102135339.GD3353@lahna.fi.intel.com>
References: <20161228161816.GA19653@bhelgaas-glaptop.roam.corp.google.com>
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 <472708904.419.1483028422817.JavaMail.zimbra@quantumtechnology.info>
 <20161229175028.GA18510@wunner.de>
 <52715138.511.1483053634089.JavaMail.zimbra@quantumtechnology.info>
 <20161230000731.GB18700@wunner.de>
 <1180505121.522.1483056977880.JavaMail.zimbra@quantumtechnology.info>
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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.