[Trac #311] OF fails to load large (~6M) initrd

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#311: OF fails to load large (~6M) initrd
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 Reporter:  dwmw2   |        Owner:  wmb at firmworks.com
     Type:  defect  |       Status:  assigned         
 Priority:  normal  |    Milestone:  BTest-2          
Component:  OFW     |   Resolution:                   
 Keywords:          |  
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Changes (by wmb at firmworks.com):

  * status:  new => assigned

Comment:

 The root cause of this problem is that OFW uses the area just below the 16
 MB boundary for driver DMA (that address was chosen some time ago, based
 on some old devices and chipsets that had only 24-bit DMA addressing).

 When loading a large ramdisk image into the standard location at 8MB, the
 loading and inflating process can end up encroaching into that DMA area.
 One manifestation is image corruption, for example when the USB host
 controller does DMA writes to its descriptor lists, thus overwriting parts
 of the image.

 The solution is to move the DMA allocation region somewhere else far out
 of harm's way.

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Ticket URL: <http://dev.laptop.org/ticket/311#comment:1>
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