#10270 HIGH Future : wlan goes missing during runin

Zarro Boogs per Child bugtracker at laptop.org
Sun Jul 17 12:00:28 EDT 2011

#10270: wlan goes missing during runin
           Reporter:  rsmith     |       Owner:  dsaxena       
               Type:  defect     |      Status:  closed        
           Priority:  high       |   Milestone:  Future Release
          Component:  kernel     |     Version:  not specified 
         Resolution:  fixed      |    Keywords:  XO-1.5 WLAN   
        Next_action:  reproduce  |    Verified:  0             
Deployment_affected:             |   Blockedby:                
           Blocking:             |  
Changes (by dsd):

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


 Further discussion with Marvell suggests that the GPIO dance is not

 There is a SD8686 bug that it cannot accept two initialisation sequences
 without a power cycle (that is what this errata was about). However, a
 SDIO-level reset was identified and confirmed by Marvell as another way of
 overcoming this limitation. Linux does this in the normal probe cycle, so
 we were never going to face this issue anyway.

 With that knowledge, I'm going to assume that this issue was fixed by
 other means and close this ticket. The GPIO tweak will remain in
 olpc-2.6.35 but be dropped from future kernels, as it seems that this is
 not needed and wouldn't have made a difference anyway. If we discover
 otherwise later, we can revive this issue and implement the GPIO tweaking
 using Linux's regulator framework.

 On a similar topic, we also made related findings: another way of working
 around this issue is to power cycle the card using normal SD bus
 mechanisms. This obviously causes a reset. And Linux's new SD runtime
 power management will cause power to be cycled during rmmod/modprobe.

 One thing to be aware of: On our motherboard, the SD card power supply is
 not clamped, so it is necessary to wait a while (approx 300ms) after
 powering the card down, before powering it up again, to ensure that this
 reset happens. However, again, as sdio_reset() happens during the probe
 path, we were never going to face this issue anyway.

  * http://article.gmane.org/gmane.linux.kernel.mmc/8605
  * http://article.gmane.org/gmane.linux.kernel.mmc/8368
  * http://article.gmane.org/gmane.linux.kernel.mmc/8388
  * http://article.gmane.org/gmane.linux.kernel.mmc/8493
  * http://article.gmane.org/gmane.linux.kernel.mmc/8634
  * http://article.gmane.org/gmane.linux.kernel.mmc/8502

Ticket URL: <http://dev.laptop.org/ticket/10270#comment:8>
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