[Trac #397] SD high-speed not working yet

[Zarro Boogs per Child]

#397: SD high-speed not working yet
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 Reporter:  cjb      |        Owner:  dilinger
     Type:  defect   |       Status:  new     
 Priority:  blocker  |    Milestone:  BTest-3 
Component:  kernel   |   Resolution:          
 Keywords:  relnote  |  
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Comment (by wmb at firmworks.com):

 The previously-cited problem with >128 block reads was a misconfiguration
 of register 4 in the CaFe SD section.  That register establishes a limit
 on the length of contiguous DMA transfers.  I had it set for 64KiB max DMA
 (128 x 512 bytes).  When I set it to it's max value of 512 KiB, I was able
 to do transfers up to 1024 blocks (512 KiB).

 With 1024-block transfers, I got 22.8 MB/sec read speed from the pq1 2 GB
 SD card.

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Ticket URL: <http://dev.laptop.org/ticket/397#comment:9>
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