On Tue, Sep 06, 2016 at 05:51:03PM +0100, Lorenzo Pieralisi wrote: > On ACPI ARM based systems the GIC interrupt controller > and corresponding interrupt model permit only the high > polarity for level interrupts. > > ACPI firmware describes PCI legacy IRQs through entries > in the _PRT objects. Entries in the _PRT can be of two types: > > - Static: not configurable, trigger/polarity default to level-low, > _PRT entry defines the global GSI interrupt number > - Configurable: _PRT interrupt entry contains a reference to the > corresponding PCI interrupt link device (that in turn provides the > interrupt descriptor through its _CRS/_PRS methods) > > Configurable IRQ entries are not currently allowed by the ACPI > specification on ARM since they can only be used for interrupt pins that > are routable, as per ACPI specifications (version 6.1, 6.2.13): > > "[...] There are two ways that _PRT can be used. Typically, the > interrupt input that a given PCI interrupt is on is configurable. For > example, a given PCI interrupt might be configured for either IRQ 10 or > 11 on an 8259 interrupt controller. In this model, each interrupt is > represented in the ACPI namespace as a PCI Interrupt Link Device. [...]" Thanks for the reference! I wouldn't read that as actually *disallowing* Interrupt Links for non-configurable interrupts. But regardless, I do understand that even if we assume Interrupt Links are allowed, there is firmware in the field that doesn't use them, and I think this patch is really targeted at *them*. > ARM platforms GIC configurations do not allow dynamic IRQ routing, > since routing is statically laid out at synthesis time; therefore PCI > interrupt links cannot be used for PCI legacy IRQ descriptions in the > _PRT on ARM systems. > > On the other hand, current core ACPI code handling PCI legacy IRQs > consider IRQ trigger/polarity for static _PRT entries as level-low. > > On ARM systems with a GIC interrupt controller and corresponding > ACPI interrupt model this does not work in that GIC interrupt > controller is only capable of handling level interrupts whose > polarity is high (for PCI legacy IRQs - that are level-low by > specification - this means that the legacy IRQs are inverted before > reaching the interrupt controller pin), resulting in IRQ allocation > failures such as: > > genirq: Setting trigger mode 8 for irq 18 failed (gic_set_type+0x0/0x48) > > Change the default polarity for PCI legacy IRQs to high on systems > booting wth ACPI on platforms with a GIC interrupt controller model, > fixing the discrepancy between specification and HW behaviour. > > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> > Acked-by: Marc Zyngier <marc.zyngier@xxxxxxx> > Tested-by: Duc Dang <dhdang@xxxxxxx> > Cc: Punit Agrawal <punit.agrawal@xxxxxxx> > Cc: Duc Dang <dhdang@xxxxxxx> > Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> > Cc: Sinan Kaya <okaya@xxxxxxxxxxxxxx> > Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx> > Cc: Marc Zyngier <marc.zyngier@xxxxxxx> > --- > v1 -> v2: > > - Added ACPI specs PCI Interrupt Link device usage restrictions in > the patch commit log for explanation > - Added review tags > > drivers/acpi/pci_irq.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/drivers/acpi/pci_irq.c b/drivers/acpi/pci_irq.c > index 2c45dd3..c576a6f 100644 > --- a/drivers/acpi/pci_irq.c > +++ b/drivers/acpi/pci_irq.c > @@ -411,7 +411,15 @@ int acpi_pci_irq_enable(struct pci_dev *dev) > int gsi; > u8 pin; > int triggering = ACPI_LEVEL_SENSITIVE; > - int polarity = ACPI_ACTIVE_LOW; > + /* > + * On ARM systems with the GIC interrupt model, level interrupts > + * are always polarity high by specification; PCI legacy > + * IRQs lines are inverted before reaching the interrupt > + * controller and must therefore be considered active high > + * as default. > + */ > + int polarity = acpi_irq_model == ACPI_IRQ_MODEL_GIC ? > + ACPI_ACTIVE_HIGH : ACPI_ACTIVE_LOW; > char *link = NULL; > char link_desc[16]; > int rc; > -- > 2.6.4 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-acpi" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
