https://bugzilla.kernel.org/show_bug.cgi?id=86351
--- Comment #23 from Andy Furniss adf.lists@gmail.com --- I don't have a 270X anymore which I was using when first commenting in this bug.
My current R9285 Tonga also has this issue and I've just tried setting 2048 (runtime) for prealloc and it doesn't help me.
I do think this is a sound driver issue though as pulse audio works, though it was a different test = with fglrx the issue is also present when using alsa but not pulse.
The difference seems to be that alsa direct uses
SND_PCM_ACCESS_RW_INTERLEAVED
and via pulse it uses
SND_PCM_ACCESS_MMAP_INTERLEAVED