[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 #14 from Takashi Iwai <tiwai at suse.de> ---
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.

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.

- 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.

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