Re: [Nouveau] [PATCH v3 0/4] nouveau RPM fixes for Optimus (final)

[Peter Wu <peter@lekensteyn.nl>]

On Fri, Jul 15, 2016 at 12:10:23PM -0400, Ilia Mirkin wrote:
> On Fri, Jul 15, 2016 at 9:12 AM, Peter Wu <peter@lekensteyn.nl> wrote:
> > Hi,
> >
> > Here are two patches to fix an issue reported on kernel bugzilla (infinite loop
> > due to unchecked function) and a more important fix to fix hanging Optimus
> > machines when runtime PM is enabled (with pm/pci patches).
> >
> > These are the final patches targeting v4.8. Changes compared to v2[1]:
> > collected R-b from Hans and Mika and fixed a minor comment style issue.
> >
> > I recommend it to be merged before the pci/pm patches[2], otherwise there is a
> > window where newer Nvidia Optimus laptops might fail to runtime resume and/or
> > lock up.  Once the pci/pm branch is merged I will propose another patch to
> > improve reliability[3].
> >
> > Known issue with patch 4: when a Nvidia HDMI audio function is present, the
> > bridge will not suspend and hence the Nvidia card will still be powered. Fixing
> 
> That's basically all optimus gpu's, right? Anything GT21x+ has a HDMI
> audio subfunction, and prior to that, the nvidia gpu tended to be the
> only gpu, or hard-muxed.
> 
> If that's the case, that's pretty much a non-starter, IMO.

For some reason the audio function tends to disappear/hide, so maybe it
is not as problematic as it appears (see
https://bugs.freedesktop.org/show_bug.cgi?id=75985). For my laptop I
also had to runtime suspend/resume before lspci -H1 shows the device,
loading with runpm=0 didn't return my HDMI audio device.

The powered on issue will also only appear on devices produced in 2013
and newer that happen to have this ACPI _PR3 ACPI method (which is quite
common for new machines supporting Windows 8 though).

For these newer laptops, after the pci/pm merge and after a patch like
http://www.spinics.net/lists/linux-pci/msg52601.html, the user can
revert to the old DSM method by booting with pcie_port_pm=off which will
retain the current behavior.

The advantage of this patch is that it fixes memory corruption on some
devices. The risk is that the card stays on because the audio subsystem
needs some more work.  FWIW, I was working on some patches that properly
suspended in presence of the HDA controller, but somehow the audio
device was not properly resumed resulting in "no AFG or MFG node found"
and "snd_hda_intel 0000:01:00.1: no codecs initialized".
-- 
Kind regards,
Peter Wu
https://lekensteyn.nl