On Tue, Sep 6, 2016 at 7:14 PM, Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote: > 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*. Right. That's my understanding too. So, generally speaking, it would be good to make interrupt links work without _PRS, _SRS under them etc. and use link objects to address this case in the future. Thanks, Rafael -- 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
