#5703 HIGH 8.2.0 (: Lid switch detection is unreliable.

[Zarro Boogs per Child]

#5703: Lid switch detection is unreliable.
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   Reporter:  cjb        |       Owner:  dilinger            
       Type:  defect     |      Status:  new                 
   Priority:  high       |   Milestone:  8.2.0 (was Update.2)
  Component:  kernel     |     Version:                      
 Resolution:             |    Keywords:  power               
Next_action:  never set  |    Verified:  0                   
  Blockedby:             |    Blocking:  6590                
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Comment(by wmb at firmworks.com):

 Further experimentation elucidates the GPIO model:

 a) The event detector senses 0 to 1 transitions of the readback bit and
 the event_enable bit gates its forwarding to the interrupt or power
 management event logic.

 b) If both edge enables are 0, the readback bit senses the state of the
 GPIO pin delayed by 2 clock edges of the 32 kHz clock.

 c) If either of the edge enables is 1, the readback bit senses
 (pos_edge_status & pos_edge_enable) | (neg_edge_status & neg_edge_enable)

 d) The reason why disabling both edge enables causes an event is because
 the readback bit switches from sensing the edge detectors to sensing the
 pin state, and if the former is 0 while the latter is 1, that causes a
 rising edge on the readback bit, triggering an event.

 e) There is a subtle difference between the positive edge sensing
 represented by both edge enables off versus the pos edge detector on.  In
 the former case, any 0 to 1 transition on the GPIO pin will retrigger the
 event detector, whereas in the latter case, retriggering can only occur
 after you clear the pos edge status bit.

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Ticket URL: <http://dev.laptop.org/ticket/5703#comment:13>
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