#12008 NORM Not Tri: Linux does not boot with Q4D20 on certain models

[Zarro Boogs per Child]

#12008: Linux does not boot with Q4D20 on certain models
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           Reporter:  Quozl                |       Owner:  wmb at firmworks.com   
               Type:  defect               |      Status:  new                 
           Priority:  normal               |   Milestone:  Not Triaged         
          Component:  ofw - open firmware  |     Version:  Development firmware
         Resolution:                       |    Keywords:                      
        Next_action:  diagnose             |    Verified:  0                   
Deployment_affected:                       |   Blockedby:                      
           Blocking:                       |  
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Comment(by wmb at firmworks.com):

 My current best guess about why (ARM) Linux is "picky" is because Linux
 uses virtual addresses above 0xc000.0000 for it' mappings (the lower
 virtual address space is for user processes).  Since there is exactly 1
 GiB of virtual address space above 0xc0000000 and some of that has to be
 reserved for things like I/O mappings and dynamically-allocated mappings,
 you can't linearly-map all of a 1 GiB physical memory in that space.  So,
 if OFW "floats" the ramdisk and flattened device tree up high in a 1 GiB
 physical memory, there is a risk that it will end up in an area that the
 kernel can't linearly map without colliding with the area it reserves for
 that other stuff.

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Ticket URL: <http://dev.laptop.org/ticket/12008#comment:3>
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