[Bug 75729] [hsw dp audio] Muting S/PDIF turns off DP

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=75729

--- Comment #3 from Mengdong Lin <mengdong.lin at intel.com> ---
Hi Martin/Jani,

Sorry for the late reply. 

I don't think this is an audio driver issue, because audio driver operations
does not directly cause screen on/off. Screen on/off is controlled by Gfx
driver.

For Haswell, the display audio devices (controller + codec) share the same
power well with display. So the audio verb excution, such as muting/unmuting
S/PDIF can wake up the audio devices and the audio driver will request power
from Graphic driver. When audio devcies are idle (in D3), the audio driver will
notify gfx driver it does not need the power. That's all. And even if the gfx
driver keeps the power well always on, it can still turn on/off the screen.

It seems to me that some user space module binds ALSA S/PDIF mute control with
screen on/off. 

Thanks
Mengdong

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