#12588 BLOC 13.2.0: XO-4 max volume produces distortion

Zarro Boogs per Child bugtracker at laptop.org
Tue Jun 4 18:09:35 EDT 2013

#12588: XO-4 max volume produces distortion
           Reporter:  dsd           |       Owner:  dsd                              
               Type:  defect        |      Status:  new                              
           Priority:  blocker       |   Milestone:  13.2.0                           
          Component:  kernel        |     Version:  Development build as of this date
         Resolution:                |    Keywords:  XO-4 Speaker Audio               
        Next_action:  add to build  |    Verified:  0                                
Deployment_affected:                |   Blockedby:                                   
           Blocking:                |  
Changes (by dsd):

  * next_action:  code => add to build


 XO-1.75 and XO-4 use different volume control techniques.

 The XO-1.75 driver effectively hardcodes the speaker volume (reg 2,
 actually it can be changed in alsamixer but not in regular UI) and drives
 the DAC volume register (reg 10) to change volume levels.

 The XO-4 driver hardcodes the DAC volume register and the volume control
 slider exposed in the UI controls the speaker/headphone volumes (reg 2 and
 reg 4).

 So matching the registers as I had tried to do before is not a valid way
 to approach this bug.

 I don't have an XO-4 C2 unit to test, but I have pushed a kernel change
 (4016fa1d6) which should help, it disables the speaker gain and drops the
 hardcoded DAC volume a bit, it sounds better on my B1.

Ticket URL: <http://dev.laptop.org/ticket/12588#comment:8>
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