#1420 BLOC Trial-2: Audio driver for AD1888 - power verification.

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#1420: Audio driver for AD1888 - power verification.
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  Reporter:  jg           |       Owner:  cjb    
      Type:  enhancement  |      Status:  new    
  Priority:  blocker      |   Milestone:  Trial-2
 Component:  kernel       |     Version:         
Resolution:               |    Keywords:  power  
  Verified:  0            |  
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Comment (by jayakumar):

 Replying to [comment:15 cjb]:
 > Works like a charm, with the LED coming on when recording starts, and
 off a short time after it ends. Thanks!

 Cool.

 > It would be nice to not have the LED come on during playback, so that
 it's only on when we're actively using the microphone -- at the moment it
 seems to come on regardless of whether the device is being used for
 playback or record.  ("aplay" turns it on, as well as the other activities
 in our builds that do audio playback)

 V_Ref bias gets turned on at resume for playback/aplay because the default
 AD1888 codec state (reg 0x76) is for V_Ref to be on.

 > Any idea what we'd need to change to achieve this?  (If you're busy, I'd
 be happy to try it out myself, given a description of what needs to be
 done.)

 If you inverted the default to be V_Ref off, then when aplay is run, the
 LED won't come on. But then it wouldn't come on when arecord is run.

 You would need to  independently track whether the user wanted to record
 in a biased Mic mode (V_Ref on, LED on) or wanted to record in an unbiased
 /analog input mode (V_Ref off, LED off). It would not be correct for
 recording to always turn on V_Ref since that would break analog input
 mode.

 I think it'd be better to have the Recording LED driven by a gpio pin and
 have the driver turn it on when recording is started/stopped rather than
 making the Recording LED depend on V_Ref bias which is a property
 independent to recording state.

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Ticket URL: <http://dev.laptop.org/ticket/1420#comment:16>
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