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Date: Thu, 27 Apr 1995 10:47:20 -0700
From: "Justin T. Gibbs" <gibbs>
Message-Id: <199504271747.KAA25865@freefall.cdrom.com>
To: CVS-commiters, cvs-sys
Subject: cvs commit: src/sys/i386/scsi aic7xxx.c aic7xxx.h
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gibbs       95/04/27 10:47:19

  Modified:    sys/dev/aic7xxx  aic7xxx.seq
  Log:
  Restructure the arbitration loop to allow for reselections that win out over
  the adapter's selections.  Many fast periferals were getting upset when
  the sequencer decided to rearbitrate after the device had already won
  arbitration.  This also forced the creation of a list threaded through
  the SCBs (since we don't have enough space anywhere else) of commands that
  are awaiting reselection.  This list is run down before any new transactions
  from the input queue are allowed.  The list is appened to whenever we begin
  a selection (simple case since the selecting device is always at the head)
  and by the kernel driver whenever a request sense occurs.  In the common
  case, the list is only one element long, but when a reselection wins out
  over a selection and that reselection generates a request sense, the
  outstanding selection required for the retreval of the sense code grows
  the list.  On machines with many targets, this might cause the list to grow
  large, so this solution, which will allow up to the maximum number of I/O
  requests capible of the card elements in the list, was chosen.  The list
  manipulation is trivial and adds three sequencer instructions of overhead
  to the selection phase.
  
  This fixes the "target busy" errors from micropolis drives and the bursty
  I/O problem when performing I/O between a Quantum Grand Prix and any other
  device.  I anticipate that this will correct many of the problems that
  have been reported with this driver.
  
  Reviewed by: Wcarchive and David Greenman

  Modified:    sys/i386/scsi  aic7xxx.c aic7xxx.h
  Log:
  Additions to support the WAITING_SCB list that the sequencer maintains.
  It is the kernel driver's responsibility to do the list manipulation whenever
  a selection timeout or a request sense occurs.
  
  Print out the interrupt type that the device has been set to.  It seems that
  one of the Asus motherboards botches this and David thought a diagnostic would
  be nice.
  
  Fix a bug in my diagnostic code that David found.
  
  Reviewed by: Wcarchive and David Greenman