#10498 NORM Not Tri: XO-1.75 RTC needs to be turned off when system powers off

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#10498: XO-1.75 RTC needs to be turned off when system powers off
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 Reporter:  wad                 |                 Owner:               
     Type:  defect              |                Status:  new          
 Priority:  normal              |             Milestone:  Not Triaged  
Component:  not assigned        |               Version:  not specified
 Keywords:  XO-1.75, XO-3, RTC  |           Next_action:  design       
 Verified:  0                   |   Deployment_affected:               
Blockedby:                      |              Blocking:               
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 The IDT1338 external RTC clock used in XO-1.75 serves two purposes: 1) it
 maintains the date/time when the SoC is powered off, and 2) it generates a
 32KHz signal to the SoC so that it properly maintains the date/time when
 powered on.

 The 32KHz signal must be enabled on power-up, and the SoC RTC must be
 initialized with the date/time from the 1338.   This is done via I2C.

 The complication comes from a little note in the data sheet that mentions
 that once enabled, the 32KHz output will continue as long as either Vcc or
 Vbat is present.   As we NEVER expect Vbat to not be present (otherwise
 the laptop forgets the date/time) we need to explicitly turn off this
 output from the external RTC in the process of powering down the laptop.

 While OFW is capable of enabling the output and initializing the SoC's RTC
 at power-up, I believe Linux has to get involved in order to turn off the
 32 KHz output when shutting down.

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Ticket URL: <http://dev.laptop.org/ticket/10498>
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