[alsa-devel] [PATCH 0/1] ALSA: hda: add fallback to polling to hdac_bus_get_response()

[Kai Vehmanen <kai.vehmanen@linux.intel.com>]

Hey all,

while debugging issues with some Intel platforms related to display
audio codec probe (see
https://lists.freedesktop.org/archives/intel-gfx/2019-October/214621.html ),
I found a discrepancy in behaviour between snd-hda-intel and SOF, despite
using the same snd-hda-codec-hdmi as the codec driver.

The specific problem I was debugging appears in a stress test
(designed to uncover the above display driver issue) where
driver-unload, s3-suspend, resume and driver-reload is done in a loop
and repeated for hundreds of iterations. When using SOF, I would get
occasional probe fail due to a missing HDA irq. The AZX snd_hda_intel
driver nicely survives this test. The explanation seems to be differences
in the hdac get_response() implementation.

While the specific issue could be solved with other means,
the git history shows a number of rare issues with HDA codecs
where polling has helped. It would seem best to align the logic
with the AZX driver implementation that has seen much more usage
over the years. This will benefit SOF and any other users of the HDAC
library.

Kai Vehmanen (1):
  ALSA: hda: add fallback to polling to hdac_bus_get_response()

 sound/hda/hdac_controller.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

-- 
2.17.1

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