• Tejun Heo's avatar
    libata: kill spurious NCQ completion detection · 459ad688
    Tejun Heo authored
    Spurious NCQ completion detection implemented in ahci was incorrect.
    On AHCI receving and processing FISes and raising interrupts are not
    interlocked and spurious interrupts are expected.
    For example, if an interrupt occurs while interrupt handler is running
    and the running interrupt handler handles the event the new IRQ
    indicated, after IRQ handler finishes, it will be executed again
    because IRQ pending bit is set by the new interrupt but there won't be
    anything to process.
    Please read the following message for more information.
    This patch...
    * Removes all spurious IRQ whining from ahci.  Spurious NCQ completion
      detection was completely wrong.  Spurious D2H Register FIS taught us
      that some early drives send spurious D2H Register FIS with I bit set
      while NCQ commands are in progress but none of recent drives does
      that and even the ones which show such behavior can do NCQ fine.
    * Kills all NCQ blacklist entries which were added because of spurious
      NCQ completions.  I tracked down each commit and verified all
      removed ones are actually added because of spurious completions.
      WD740ADFD-00NLR1 wasn't deleted but moved upward because the drive
      not only had spurious NCQ completions but also is slow on sequential
      data transfers if NCQ is enabled.
      Maxtor 7V300F0 was added by 0e3dbc01
      from Alan Cox.  I can only find evidences that the drive only had
      troubles with spuruious completions by searching the mailing list.
      This entry needs to be verified and removed if it doesn't have other
      NCQ related problems.
    Signed-off-by: default avatarTejun Heo <htejun@gmail.com>
    Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
    Signed-off-by: default avatarJeff Garzik <jeff@garzik.org>
ahci.c 61.9 KB