1. Jul 02, 2016
    • Sinan Kaya's avatar
      ACPI,PCI,IRQ: factor in PCI possible · 4a6e68bf
      Sinan Kaya authored
      The change introduced in commit 103544d8 (ACPI,PCI,IRQ: reduce
      resource requirements) omitted the initially applied PCI_POSSIBLE
      penalty when the IRQ is active.
      
      Incorrect calculation of the penalty leads the ACPI code to assigning
      a wrong interrupt number to a PCI INTx interrupt.
      
      This would not be as bad as it sounds in theory.  It would just cause
      the interrupts to be shared and result in performance penalty.
      
      However, some drivers (like the parallel port driver) don't like
      interrupt sharing and in the above case they will causes all of
      the PCI drivers wanting to share the interrupt to be unable to
      request it.
      
      The issue has not been caught in testing because the behavior is
      platform-specific and depends on the peripherals ending up sharing
      the IRQ and their drivers.
      
      Before the above commit the code would add the PCI_POSSIBLE value
      divided by the number of possible IRQ users to the IRQ penalty
      during initialization.
      
      Later in that code path, if the IRQ is chosen as the active IRQ or
      if it is used by ISA; additional penalties are added.
      
      Fixes: 103544d8
      
       (ACPI,PCI,IRQ: reduce resource requirements)
      Signed-off-by: default avatarSinan Kaya <okaya@codeaurora.org>
      Tested-by: default avatarWim Osterholt <wim@djo.tudelft.nl>
      [ rjw: Changelog ]
      Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
      4a6e68bf
  2. Jun 30, 2016
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