[Trac #1382] "reboot" from Linux just gives black screen on LX

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#1382: "reboot" from Linux just gives black screen on LX
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 Reporter:  cjb     |        Owner:  dilinger 
     Type:  defect  |       Status:  new      
 Priority:  normal  |    Milestone:  Untriaged
Component:  kernel  |   Resolution:           
 Keywords:          |  
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Comment (by dilinger):

 Ok, this black screen is the "screen blanking" feature of DCON; that's
 where it comes from.  The backlight is also shut off by the kernel's
 reboot notifier, so that's why we see the non-backlit screen.  The problem
 is that writing 0x2 (the DCON Sleep Mode bit) to the DCON register
 *should* disable power to the panel; that doesn't happen.  Instead, the
 0x2 write is being ignored, and the panel is remaining on.

 One can test this from OFW; 'dev screen', ' 2 mode!' (or any other bits
 from the DCON spec).  The panel on b2 will turn off; pre-b3, it remains
 on.

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Ticket URL: <http://dev.laptop.org/ticket/1382#comment:2>
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