#12353 BLOC Not Tri: DT should indicate new external SD power switch capabilities on XO-4 C2

[Zarro Boogs per Child]

#12353: DT should indicate new external SD power switch capabilities on XO-4 C2
---------------------------------+------------------------------------------
 Reporter:  wad                  |                 Owner:  wmb at firmworks.com
     Type:  defect               |                Status:  new              
 Priority:  blocker              |             Milestone:  Not Triaged      
Component:  ofw - open firmware  |               Version:  4-B1             
 Keywords:  XO-4 C2              |           Next_action:  code             
 Verified:  0                    |   Deployment_affected:                   
Blockedby:                       |              Blocking:  2                
---------------------------------+------------------------------------------
 On XO-4 motherboards indicated by a 4C1 board ID or earlier, the external
 SD power switch is only capable of operation at +3.3V.

 On motherboard indicated by a 4C2 board ID or later, the external SD power
 switch is capable of operation at both +1.8V and +3.3V.

 The OFW device tree entry for 4C2 or later motherboard should reflect
 this.

 The minimum delay between turning off the external SD power and turning it
 back on should be 10 mS.    There is no harm in changing the voltage
 selection while the power is enabled, although the SD spec requires that
 power be turned off, then turned back on at the different voltage.

 GPIO 115 on the SoC now controls power to the external SD card. If
 asserted low, the SD card is powered. (Previously, power to the external
 SD card was under control of the EC).

 GPIO116 selects what voltage to provide to the SD card. If high, the SD
 card is powered with +1.8V.  If low, the SD card is powered with +3.3V.

 The hardware ECO for C1 motherboards is described at:
 http://wiki.laptop.org/go/XO4_C1_ECOs#External_SD_Power_Switch

-- 
Ticket URL: <http://dev.laptop.org/ticket/12353>
One Laptop Per Child <http://laptop.org/>
OLPC bug tracking system