By the time ACPI gets initialized, this code tries to determine an IRQ number based on penalty values in this array. It will try to locate the IRQ with the least penalty assignment so that interrupt sharing is avoided if possible. A couple of notes about the external APIs: 1. These API can be called before the ACPI is started. Therefore, one cannot assume that the PCI link objects are initialized for calculating penalties. 2. The polarity and trigger information passed via the acpi_penalize_sci_irq from the BIOS may not match what the IRQ subsystem is reporting as the call might have been placed before the IRQ is registered by the interrupt subsystem. The reverted changes were in the direction to remove these external API and try to calculate the penalties at runtime for the ISA, SCI as well as PCI IRQS. This didn't work out well with the existing platforms. V5: * clean up the commit message for 1/3 and 2/3 * drop 3/3 * bring back ACPI, PCI IRQ: add PCI_USING penalty for ISA interrupts as 3/3 V4: https://www.spinics.net/lists/arm-kernel/msg537158.html * Drop ACPI, PCI IRQ: add PCI_USING penalty for ISA interrupts * A new patch to isolate early boot ISA penalty calculations from dynamic penalty calculation by directly modifying the array members in ("ACPI, PCI, IRQ: assign ISA IRQ directly during early boot stages") * Now that we isolated both SCI and ISA interrupts, revert commit ("Revert "ACPI,PCI,IRQ: separate ISA penalty calculation"") and commit ("487cf917ed0d (Revert "ACPI, PCI, IRQ: remove redundant code in acpi_irq_penalty_init()") to share code between ISA and PCI penalties as originally intended. V3: http://www.spinics.net/lists/arm-kernel/msg536208.html * drop patch #1 as discussed with Bjorn * add patch #3 to track SCI irq and penalty separately V2: https://lkml.org/lkml/2016/10/1/106 * Commit message updates V1: http://lists-archives.com/linux-kernel/28673954-revert-acpi-pci-irq-reduce-static-irq-array-size-to-16.html * initial implementation Sinan Kaya (3): ACPI, PCI, IRQ: assign ISA IRQ directly during early boot stages ACPI: pci_link: penalize SCI correctly ACPI: pci_link: Include PIRQ_PENALTY_PCI_USING for ISA IRQs arch/x86/kernel/acpi/boot.c | 1 + drivers/acpi/pci_link.c | 38 +++++++++++++++++++++----------------- include/linux/acpi.h | 1 + 3 files changed, 23 insertions(+), 17 deletions(-) -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
