#12916 NORM Future : alc5631 pops at capture start

Zarro Boogs per Child bugtracker at laptop.org
Thu Sep 10 18:32:10 EDT 2015

#12916: alc5631 pops at capture start
     Reporter:  Quozl                |                 Owner:  Quozl
         Type:  defect               |                Status:  new
     Priority:  normal               |             Milestone:  Future
    Component:  kernel               |  Release
     Keywords:                       |               Version:  Development
     Blocking:                       |  source as of this date
Action Needed:  review               |            Blocked By:
                                     |  Deployments affected:
                                     |              Verified:  0
 Pops, or unplanned signal swings, are at the start of captures made
 through the microphone or input socket on the XO-1.75 and XO-4.

 See also #9640 for similar problem on XO-1.5.

 See also #12289 for a test method for DMA that relies on the pops.

 Is mostly solved on XO-1.75 by moving the register changes to the
 ''.startup'' operation, followed by a small delay of 340ms.  The register
 changes that cause pops are;
  * turning on Vref,
  * turning off Vref fast,
  * turning on the record mixer block,
  * turning on the microphone bias block,
  * turning on the microphone boost gain block,
  * turning on the ADC block, and;
  * turning on i²s serial data port,

 That pops are also caused by the microphone boost gain block and i²s
 serial data port was not properly handled by the released driver in 13.2.5
 and earlier.

 Test case: present silence or a test tone to the laptop under test, then
 run arecord at all sample rates, both mono or stereo, play back the files,
 and examine the files using audacity.

 for rate in 8000 11025 16000 22050 32000 44100 48000 88200 96000; do
   for channels in 1 2; do
     arecord --file-type=wav --channels=$channels --format=S16_LE \
         --rate=$rate --duration=1 /tmp/x.$channels.$rate.wav
     sleep 2
     aplay /tmp/x.$channels.$rate.wav

Ticket URL: <http://dev.laptop.org/ticket/12916>
One Laptop per Child <http://one.laptop.org/>
One Laptop per Child bug tracking system

More information about the Bugs mailing list