[Trac #839] MMC has timeout problems

[Zarro Boogs per Child]

#839: MMC has timeout problems
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 Reporter:  PierreOssman  |        Owner:  mlj     
     Type:  defect        |       Status:  assigned
 Priority:  normal        |    Milestone:  BTest-3 
Component:  hardware      |   Resolution:          
 Keywords:                |  
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Comment (by PierreOssman):

 Marvell found the problem:

 "Basically, the OLPC board have a pull down resister on the SD_DATA[3], as
 for most of
 the MMC new card, and all the SD mem card have internal pull up on
 SD_DATA[3].

 but some older MMC cards don't have pull up on SD_DATA[3], that is why
 they will not work in
 the current OLPC board."

 I tested turning of 4-bit transfers, and now mmc works fine. So if this
 resistor issue can be resolved we should have full support for MMCv4 as
 well.

 (Note that MMCv3 is still broken)

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Ticket URL: <http://dev.laptop.org/ticket/839#comment:3>
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