On Thu, Oct 20, 2016 at 08:58:14PM -0500, Bjorn Helgaas wrote:

On Wed, Oct 19, 2016 at 06:21:03PM -0400, Sinan Kaya wrote:

quoted

The SCI penalize function was removed in two steps (first refactor
and then remove) and these changes are reverted here in one go.

The commit 103544d86976 ("ACPI,PCI,IRQ: reduce resource requirements")
refactored the original code so that SCI penalty is calculated dynamically
by the time get_penalty function is called. That change is partially
reverted here, specifically for the SCI IRQ alone.

The SCI penalize function was finally dropped by commit 9e5ed6d1fb87
("ACPI,PCI,IRQ: remove SCI penalize function") that replaced the old SCI
penalty API with penalty calculation carried out dynamically and based
on the acpi_gbl_FADT.sci_interrupt value.

However, that new algorithm relies on the accurate setting of IRQ
types and that doesn't happen early enough on some platforms which
leads to incorrect penalty assignments for PCI IRQs.  In those cases,
irq_get_trigger_type() returns incorrect values for the IRQs in
question, because they have not been registered yet by the time the
penalties are calculated.

To fix this problem, we only need to fix the penalty for the SCI interrupt.
It seems better to add a single "sci_penalty" variable, set it to
PIRQ_PENALTY_PCI_USING if it's level/low or PIRQ_PENALTY_ISA_ALWAYS
otherwise, and add "sci_penalty" in when appropriate.  That should fix it
for *any* SCI IRQ, not just those less than 256, and we don't have to add
these extra penalty table entries that are all unused (except possibly for
one entry if we have an SCI in the 16-255 range).

For this reason, revert commit 9e5ed6d1fb87 ("ACPI,PCI,IRQ: remove SCI
penalize function") completely to restore the correct behavior.

I like this patch fine, except for the changelog.  I don't think it's
useful to describe this as a revert and give all the historical
details.  I think the important part is something like this:

  We previously used irq_get_trigger_type(irq) to help compute the
  penalty for the SCI, but that depends on the SCI having been
  registered already.  Add acpi_penalize_sci_irq() so platforms can
  tell us the SCI IRQ, trigger, and polarity so we can compute the
  penalty even before the SCI has been registered.

I think this is actually the critical patch that fixes the regression
reported by Ondrej, so the changelog really should include details
about the regression, e.g., something like this:

  ACPI: pci_link: Penalize SCI correctly

  Ondrej reported that IRQs stopped working in v4.7 on several
  platforms.  A typical scenario, from Ondrej's VT82C694X/694X, is:

    ACPI: Using PIC for interrupt routing
    ACPI: PCI Interrupt Link [LNKA] (IRQs 1 3 4 5 6 7 10 *11 12 14 15)
    ACPI: No IRQ available for PCI Interrupt Link [LNKA]
    8139too 0000:00:0f.0: PCI INT A: no GSI

  We're using PIC routing, so acpi_irq_balance == 0, and LNKA is already
  active at IRQ 11.  In that case, acpi_pci_link_allocate() only tries
  to use the active IRQ (IRQ 11) which also happens to be the SCI.

  We should penalize the SCI by PIRQ_PENALTY_PCI_USING, but
  irq_get_trigger_type(11) returns something other than
  IRQ_TYPE_LEVEL_LOW, so we penalize it by PIRQ_PENALTY_ISA_ALWAYS
  instead, which makes acpi_pci_link_allocate() assume the IRQ isn't
  available and give up.

  Add acpi_penalize_sci_irq() so platforms can tell us the SCI IRQ,
  trigger, and polarity directly and we don't have to depend on
  irq_get_trigger_type().

  Link: http://lkml.kernel.org/r/201609251512.05657.linux at rainbow-software.org
  Reported-by: Ondrej Zary [off-list ref]

I don't understand what's broken about using irq_get_trigger_type().
The SCI is registered in the following path, which is certainly before
we try to enable LNKA for the 8139too device:

  acpi_init                                           # subsys_initcall
    acpi_bus_init
      acpi_enable_subsystem
	acpi_ev_install_xrupt_handlers
	  acpi_ev_install_sci_handler
	    acpi_os_install_interrupt_handler(sci_interrupt, ...)
	      acpi_gsi_to_irq
		acpi_register_gsi
		  irq_create_fwspec_mapping
		    irqd_set_trigger_type

In any event, I think this patch to add acpi_penalize_sci_irq() is
fine.

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

quoted

Link: https://lkml.org/lkml/2016/10/4/283
Signed-off-by: Sinan Kaya <redacted>
Fixes: commit 103544d86976 ("ACPI,PCI,IRQ: reduce resource requirements")
Fixes: commit 9e5ed6d1fb87 ("ACPI,PCI,IRQ: remove SCI penalize function")

"commit" is redundant; it's sufficient to say:

  Fixes: 103544d86976 ("ACPI,PCI,IRQ: reduce resource requirements")

In fact, I don't think you really need to include "commit" in the
reference to 9e5ed6d1fb87 above either.

quoted

---
 arch/x86/kernel/acpi/boot.c |  1 +
 drivers/acpi/pci_link.c     | 30 +++++++++++++++---------------
 include/linux/acpi.h        |  1 +
 3 files changed, 17 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 90d84c3..0ffd26e 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c

@@ -453,6 +453,7 @@ static void __init acpi_sci_ioapic_setup(u8 bus_irq, u16 polarity, u16 trigger,
 		polarity = acpi_sci_flags & ACPI_MADT_POLARITY_MASK;
 
 	mp_override_legacy_irq(bus_irq, polarity, trigger, gsi);
+	acpi_penalize_sci_irq(bus_irq, trigger, polarity);
 
 	/*
 	 * stash over-ride to indicate we've been here

diff --git a/drivers/acpi/pci_link.c b/drivers/acpi/pci_link.c
index 4f37938..294b190 100644
--- a/drivers/acpi/pci_link.c
+++ b/drivers/acpi/pci_link.c

@@ -87,6 +87,7 @@ struct acpi_pci_link {
 
 static LIST_HEAD(acpi_link_list);
 static DEFINE_MUTEX(acpi_link_lock);
+static int sci_irq = -1, sci_penalty;
 
 /* --------------------------------------------------------------------------
                             PCI Link Device Management

@@ -496,25 +497,13 @@ static int acpi_irq_get_penalty(int irq)
 {
 	int penalty = 0;
 
-	/*
-	* Penalize IRQ used by ACPI SCI. If ACPI SCI pin attributes conflict
-	* with PCI IRQ attributes, mark ACPI SCI as ISA_ALWAYS so it won't be
-	* use for PCI IRQs.
-	*/
-	if (irq == acpi_gbl_FADT.sci_interrupt) {
-		u32 type = irq_get_trigger_type(irq) & IRQ_TYPE_SENSE_MASK;
-
-		if (type != IRQ_TYPE_LEVEL_LOW)
-			penalty += PIRQ_PENALTY_ISA_ALWAYS;
-		else
-			penalty += PIRQ_PENALTY_PCI_USING;
-	}
+	if (irq == sci_irq)
+		penalty += sci_penalty;
 
 	if (irq < ACPI_MAX_ISA_IRQS)
 		return penalty + acpi_isa_irq_penalty[irq];
 
-	penalty += acpi_irq_pci_sharing_penalty(irq);
-	return penalty;
+	return penalty + acpi_irq_pci_sharing_penalty(irq);
 }
 
 int __init acpi_irq_penalty_init(void)

@@ -881,6 +870,17 @@ bool acpi_isa_irq_available(int irq)
 		    acpi_irq_get_penalty(irq) < PIRQ_PENALTY_ISA_ALWAYS);
 }
 
+void acpi_penalize_sci_irq(int irq, int trigger, int polarity)
+{
+	sci_irq = irq;
+
+	if (trigger == ACPI_MADT_TRIGGER_LEVEL &&
+	    polarity == ACPI_MADT_POLARITY_ACTIVE_LOW)
+		sci_penalty = PIRQ_PENALTY_PCI_USING;
+	else
+		sci_penalty = PIRQ_PENALTY_ISA_ALWAYS;
+}
+
 /*
  * Over-ride default table to reserve additional IRQs for use by ISA
  * e.g. acpi_irq_isa=5

diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index c5eaf2f..67d1d3e 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h

@@ -318,6 +318,7 @@ struct pci_dev;
 int acpi_pci_irq_enable (struct pci_dev *dev);
 void acpi_penalize_isa_irq(int irq, int active);
 bool acpi_isa_irq_available(int irq);
+void acpi_penalize_sci_irq(int irq, int trigger, int polarity);
 void acpi_pci_irq_disable (struct pci_dev *dev);
 
 extern int ec_read(u8 addr, u8 *val);

-- 
1.9.1


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