On Wed, Oct 19, 2016 at 06:21:02PM -0400, Sinan Kaya wrote:

The penalty determination of ISA IRQ goes through 4 paths.
1. assign PCI_USING during power up via acpi_irq_penalty_init.
2. update the penalty with acpi_penalize_isa_irq function based on the
active parameter.
3. kernel command line penalty update via acpi_irq_penalty_update function.
4. increment the penalty as USING right after the IRQ is assign to PCI.

acpi_penalize_isa_irq and acpi_irq_penalty_update functions get called
before the ACPI subsystem is started.

These API need to bypass the acpi_irq_get_penalty function.

I don't mind this patch, but the changelog doesn't tell me what's
broken and why we need this fix.  Apparently acpi_irq_get_penalty()
doesn't work before ACPI is initialized, but I don't see *why* it
wouldn't work.

However, I see one bug it *does* fix: we do not store the SCI penalty
in the acpi_isa_irq_penalty[] table because acpi_isa_irq_penalty[]
only holds ISA IRQ penalties, and there's no guarantee that the SCI is
an ISA IRQ.  But prior to this patch, we added in the SCI penalty to
the acpi_isa_irq_penalty[] entry when the SCI was an ISA IRQ, which
makes acpi_irq_get_penalty() return the wrong thing.  Consider:

  Initially     acpi_isa_irq_penalty[9] = 0.
  Assume        sci_interrupt = 9.
  Then          acpi_irq_get_penalty(9) returns X.
  If we call    acpi_penalize_isa_irq(9, 1),
  it sets       acpi_isa_irq_penalty[9] = X,
  and now       acpi_irq_get_penalty(9) returns X + X.

I'd propose a changelog like this:

  We do not want to store the SCI penalty in the acpi_isa_irq_penalty[]
  table because acpi_isa_irq_penalty[] only holds ISA IRQ penalties and
  there's no guarantee that the SCI is an ISA IRQ.  We add in the SCI
  penalty as a special case in acpi_irq_get_penalty().

  But if we called acpi_penalize_isa_irq() or acpi_irq_penalty_update()
  for an SCI that happened to be an ISA IRQ, they stored the SCI
  penalty (part of the acpi_irq_get_penalty() return value) in
  acpi_isa_irq_penalty[].  Subsequent calls to acpi_irq_get_penalty()
  returned a penalty that included *two* SCI penalties.

If this actually fixes a worse problem related to ACPI initialization,
of course you should detail that.

Acked-by: Bjorn Helgaas <bhelgaas@google.com>