• Tejun Heo's avatar
    libata: implement spurious irq handling for SFF and apply it to piix · 27943620
    Tejun Heo authored
    Traditional IDE interface sucks in that it doesn't have a reliable IRQ
    pending bit, so if the controller raises IRQ while the driver is
    expecting it not to, the IRQ won't be cleared and eventually the IRQ
    line will be killed by interrupt subsystem.  Some controllers have
    non-standard mechanism to indicate IRQ pending so that this condition
    can be detected and worked around.
    
    This patch adds an optional operation ->sff_irq_check() which will be
    called for each port from the ata_sff_interrupt() if an unexpected
    interrupt is received.  If the operation returns %true,
    ->sff_check_status() and ->sff_irq_clear() will be cleared for the
    port.  Note that this doesn't mark the interrupt as handled so it
    won't prevent IRQ subsystem from killing the IRQ if this mechanism
    fails to clear the spurious IRQ.
    
    This patch also implements ->sff_irq_check() for ata_piix.  Note that
    this adds slight overhead to shared IRQ operation as IRQs which are
    destined for other controllers will trigger extra register accesses to
    check whether IDE interrupt is pending but this solves rare screaming
    IRQ cases and for some curious reason also helps weird BIOS related
    glitch on Samsung n130 as reported in bko#14314.
    
      http://bugzilla.kernel.org/show_bug.cgi?id=14314
    
    * piix_base_ops dropped as suggested by Sergei.
    
    * Spurious IRQ detection doesn't kick in anymore if polling qc is in
      progress.  This provides less protection but some controllers have
      possible data corruption issues if the wrong register is accessed
      while a command is in progress.
    Signed-off-by: default avatarTejun Heo <tj@kernel.org>
    Reported-by: default avatarJohannes Stezenbach <js@sig21.net>
    Reported-by: default avatarHans Werner <hwerner4@gmx.de>
    Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
    Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>
    Signed-off-by: default avatarJeff Garzik <jgarzik@redhat.com>
    27943620
libata-sff.c 78.6 KB