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

[Lukas Wunner <lukas@wunner.de>]

On Tue, Jan 03, 2017 at 05:31:30PM +0100, Peter Wu wrote:
> On Tue, Jan 03, 2017 at 05:11:23PM +0100, Lukas Wunner wrote:
> > On Tue, Jan 03, 2017 at 04:15:47PM +0100, Peter Wu wrote:
> > > The acpidump from the bug does not show known issues, it *looks* fine.
> > > There have been other issues related to resuming power on newer Nvidia
> > > hardware (https://bugs.freedesktop.org/show_bug.cgi?id=94725,
> > > https://bugzilla.kernel.org/show_bug.cgi?id=156341) but there is not
> > > much progress here.  (The last time I traced the PCIe register accesses
> > > (via kprobes) and tried to disable some of those, it still did not help
> > > with preventing the power issue.)
> > 
> > It seems that the _DSM method works on Kilian's laptop.  Would it be
> > viable to default to _DSM if it's available, and only use _PR3 if not?
> 
> DSM should not be preferred when PR3 is available:
> 
>  - After MS introduced D3cold (PR3) support to Win8+, vendors are
>    unlikely to test legacy DSM and the likelihood of breakage increases.
>  - On one Lenovo laptop, the DSM method causes memory corruption while
>    PR3 fixes this problem.
>  - On some laptops, DSM keeps the fan on while PR3 stopped the noise.
>  - On some laptops, DSM does not really power off the GPU and results in
>    increased power consumption during runtime/system sleep. PR3 fully
>    removes the power, as desired.

I see.  How about adding an "optimus" module_param to nouveau which
allows users to force either DSM or PR3 on machines where the method
selected by default doesn't work properly?  At least until we've
figured out how to always select the correct method, or have debugged
the remaining issues with PR3?

When selecting DSM, I guess pci_d3cold_disable() would have to be
called to prevent usage of both methods, right?

Thanks,

Lukas