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  hda driver initialization takes too much time on the machine with
  coffeelake audio controller [8086:a348]

Status in HWE Next:
Status in linux package in Ubuntu:
Status in linux-oem package in Ubuntu:
Status in linux source package in Xenial:
Status in linux-oem source package in Xenial:
  Fix Committed
Status in linux source package in Artful:
  Fix Committed
Status in linux-oem source package in Artful:

Bug description:

  We have a couple of laptop and desktop computers, all of them are cfl 
  and all of them have cfl audio controller [8086:a348], and these computers 
  different realtek codecs on them (alc256, alc255, alc289 and ...). The hda
  driver takes too much time (3 secs - 8 secs) to initialize on these machines.
  This problem never happened on kbl, skl, bdw, ... before.

  Sometimes this can make pulseaudio can't work well.

  pulseaudio starts, but the driver (as kernel modules) initialization has not
  finished, then there is no valid sink in the pulseaudio. At this moment, some 
  Apps already start using pulseaudio to play sound, but users can't hear the 
  as expected. This problem never happened before, it is exposed on cfl 
  and all cfl platforms (with audio controller 8086:a348) have this problem.

  Set the polling mode can fix this problem, and this workaround is in the
  mainline kernel.

  [Test Case]
  Boot the machine and check the dmesg, from the hda log, we can see the driver
  initialization is finished within 0.1s and pulseaudio works well.

  [Regression Potential]
  No regression, this fix is only for CFL audio controller (8086:a348), and
  in theory, polling mode is safe for all audio controllers, using interrupt
  mode rather than polling mode on other platforms just wants to save polling
  overhead for CPUs, since interrupt mode can't work well on CFL platform, we
  have to use polling mode.

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