Nouveau - Jul 2016 - [PATCH v3 0/4] nouveau RPM fixes for Optimus (final)

On Fri, Jul 15, 2016 at 12:10 PM, Ilia Mirkin <imirkin at alum.mit.edu>
wrote:
> On Fri, Jul 15, 2016 at 9:12 AM, Peter Wu <peter at 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.
I'd imagine there is a strap on the asic so the audio function is only
enabled if there is a connector actually wired to the dGPU.  It
doesn't make much sense to expose audio if there is no way to use it.

Alex

On Fri, Jul 15, 2016 at 12:27 PM, Alex Deucher <alexdeucher at gmail.com>
wrote:
> On Fri, Jul 15, 2016 at 12:10 PM, Ilia Mirkin <imirkin at
alum.mit.edu> wrote:
>> On Fri, Jul 15, 2016 at 9:12 AM, Peter Wu <peter at
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.
>
> I'd imagine there is a strap on the asic so the audio function is only
> enabled if there is a connector actually wired to the dGPU.  It
> doesn't make much sense to expose audio if there is no way to use it.
A lot of the time, there actually is a connector wired up. A lot of
the other time, there is no connector, but the display unit is still
there. Very recently, NVIDIA gpu's have started coming out marked as
"3d accelerator", which sometimes but not always means that
there's no
display unit, and for those, I would assume there is no audio
subfunction.

However this is a fraction of all devices using runpm.

  -ilia

On Fri, Jul 15, 2016 at 12:31 PM, Ilia Mirkin <imirkin at alum.mit.edu>
wrote:
> On Fri, Jul 15, 2016 at 12:27 PM, Alex Deucher <alexdeucher at
gmail.com> wrote:
>> On Fri, Jul 15, 2016 at 12:10 PM, Ilia Mirkin <imirkin at
alum.mit.edu> wrote:
>>> On Fri, Jul 15, 2016 at 9:12 AM, Peter Wu <peter at
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.
>>
>> I'd imagine there is a strap on the asic so the audio function is
only
>> enabled if there is a connector actually wired to the dGPU.  It
>> doesn't make much sense to expose audio if there is no way to use
it.
>
> A lot of the time, there actually is a connector wired up. A lot of
> the other time, there is no connector, but the display unit is still
> there. Very recently, NVIDIA gpu's have started coming out marked as
> "3d accelerator", which sometimes but not always means that
there's no
> display unit, and for those, I would assume there is no audio
> subfunction.
>
Just because there is a display block, doesn't mean the audio function
is always enabled.  I suspect it is disabled by hardware straps on
systems with no display connectors or other specific OEM configs.

Alex