[Bug 74861] [hsw] Fast audio playback on Intel Haswell HDMI due to runtime pm

[bugzilla-daemon at bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=74861

--- Comment #16 from Takashi Iwai <tiwai at suse.de> ---
(In reply to Peter Curtis from comment #15)
> (In reply to Takashi Iwai from comment #14)
> > OK, now it's getting more interesting.  In Peter's case, eld#* don't show
> > the ELD, thus it cannot work at all.  Unless he is willing to test without
> > Nvidia driver, we cannot help at all.  One of principles of debugging is to
> > isolate the problem.  Using Nvidia driver makes it impossible.
> I had assumed Bumbleebee had disabled the driver and I have tested with and
> without the driver via bummblebee. I have no problem booting without the
> nVidia driver if there is a suitable boot option you can give me - I had to
> use nouveau.modeset=0 to disable the nouveau driver in some kernels to get a
> successful boot, is there a similar one to inhibit nVidia?

I guess module blacklist should work.  But, the easiest hack would be just to
remove kernel module files.  And, don't forget to rebuild initrd if such
modules are included in there.

> > Meanwhile, in Daniel's case, the audio driver itself receives ELD properly,
> > and the powerwell refcount isn't zero.  So, this looks as if it should work
> > indeed, and worth to take a deeper look.
> > 
> > How is i915_power_domain_info in the working case (i.e. with
> > i915.disable_power_well=0)?
> > 
> > Also, checking the following would be helpful to understand the problem:
> > 
> > - Can the machine boot without Nvidia graphics?  Some BIOS can disable it. 
> > This reduces the possible bad interaction and concentrate on i915 driver.
> Nothing in Bios settings in my case

OK.

> > - Boot with drm.debug=0x0e option and take the dmesg output for both working
> > and non-working cases.
> > 
> > - Install intel-gpu-tools package and run intel_reg_dumper and
> > intel_audio_dump programs, save the outputs for both working and non-working
> > cases.
> > 
> > - Test with power_save_controller=0 option for snd-hda-intel instead of
> > i915.disable_power_well=0 option.
> Are any of the above useful even with nVidia drivers?

Yes, but let's begin with the simplified use case, Intel-only.

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