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  1. Mar 10, 2014
    • Stephen Warren's avatar
      ush: ehci: initialize altnext pointers in QH · 2456b97f
      Stephen Warren authored
      
      Section 4.10.2 "Advance Queue" of ehci-specification-for-usb.pdf
      specifies how an EHCI controller loads a new QTD for processing if the
      QH is not already marked as active. It states:
      
      =====
      If the field Bytes to Transfer is not zero and the T-bit in the Alternate
      Next qTD Pointer is set to zero, then the host controller uses the
      Alternate Next qTD Pointer. Otherwise, the host controller uses the Next
      qTD Pointer. If Next qTD Pointer’s T-bit is set to a one, then the host
      controller exits this state and uses the horizontal pointer to the next
      schedule data structure.
      =====
      
      Hence, we must ensure that the alternate next QTD pointer's T-bit
      (TERMINATE) is set, so the EHCI controller knows to use the next QTD
      pointer.
      
      Signed-off-by: default avatarStephen Warren <swarren@nvidia.com>
      2456b97f
  2. Mar 08, 2014
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