This is an intentional duplicate of Bug 60769, because the ALSA-specific part of that bug got fixed, all that is left is a bad interaction between i915 and iommu, and that requires a different person to handle. But I can't reassign bugs.
On all Haswell hardware, if you don't provide the intel_iommu=igfx_off option (and your distro defaults to intel_iommu=on), then attempts to output audio via HDMI will lead to undesired behaviour that is different between systems. On some systems, audio crackles, on others the audio stream immediately hangs.
I chatted to Daniel Vetter, he says that it is wrong to assign it to the graphics driver. Please reassign to the IOMMU component.
Dupe of bug 67321 and/or bug 86221?
This bug, bug 67321, bug 60769 and bug 86221 are indeed the same.
*** This bug has been marked as a duplicate of bug 60769 ***
Alan, if you mark this as a dupe, then please also fix the component and the responsible person on bug 60769. My inability to fix this fields is the reason of creating a duplicate - if the "primary" bug is assigned to an ALSA person, there is absolutely no chance that an IOMMU person will look at it.
The DMA/IOMMU person is on the CC of 60769 already (email@example.com)