#12687 NORM Not Tri: Can the AC check be eliminated or replaced?

[Zarro Boogs per Child]

#12687: Can the AC check be eliminated or replaced?
-------------------------------------------+--------------------------------
           Reporter:  jvonau               |       Owner:  Quozl        
               Type:  enhancement          |      Status:  closed       
           Priority:  normal               |   Milestone:  Not Triaged  
          Component:  ofw - open firmware  |     Version:  not specified
         Resolution:  wontfix              |    Keywords:               
        Next_action:  never set            |    Verified:  0            
Deployment_affected:  Australia            |   Blockedby:               
           Blocking:                       |  
-------------------------------------------+--------------------------------
Changes (by Quozl):

  * status:  new => closed
  * resolution:  => wontfix


Comment:

 The ''?enough-power'' check requires:
  * external DC power,
  * a battery present,
  * the battery management system not to report the battery low condition.

 The reflashing process erases the device before writing to it.  Erasure is
 a necessary prelude to writing.  The algorithm works on a 65536 byte block
 at a time, rather than the whole device at a time, in order to reduce
 risk.  Even so, loss of power during the critical period does brick the
 machine.  We have tested this.  The critical period is a few seconds, and
 varies according to the endurance and product life of the SPI FLASH chip,
 and the temperature.

 External DC power can be immediately lost if:
  * the DC plug is pulled out,
  * the DC plug is faulty,
  * the cable is faulty,
  * the DC socket is faulty,
  * the laptop power input circuit is faulty.

 External DC power can be lost within milliseconds if:
  * the AC adapter is faulty,
  * the AC socket is faulty,
  * the AC plug is faulty,
  * the AC plug is pulled out,
  * the AC cable is faulty,
  * the other end AC plug is faulty,
  * the other end AC plug is pulled out,
  * the power socket is faulty,
  * the power switch is faulty,
  * the power switch is turned off,
  * the supply of AC power is lost.

 Internal DC battery power can be lost if:
  * the battery has insufficient stored charge, (combined with a surge in
 demand causing the voltage to decrease below a critical operating level),
  * the latches are not fully closed,
  * the battery connector on the laptop is faulty,
  * the battery connector on the battery is faulty,
  * the laptop is vibrated, combined with a faulty connection,
  * the laptop is heated or cooled, combined with a faulty connection,
  * the laptop battery interface circuit is faulty.

 We don't plan to change this check for OLPC OS, so I shall close this
 ticket.

 If you are willing to take the risk as a deployment, you might reimplement
 the ''?enough-power'' check in your boot/olpc.fth.  I also suggest
 compensating controls, such as adding warnings and a prompt asking the
 user to confirm they will not remove the battery during the reflash.
 Ensuring you have debricking capability would also be a good control.

 If you need assistance for this change, please contact OLPC directly, and
 we will manage the issue outside the OLPC OS development process.  Thanks!

-- 
Ticket URL: <http://dev.laptop.org/ticket/12687#comment:3>
One Laptop Per Child <http://laptop.org/>
OLPC bug tracking system