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schemas: pci: bridge: Document WAKE# interrupt properties #126

Open Mani-Sadhasivam opened 9 months ago

Mani-Sadhasivam commented 9 months ago

WAKE# sideband interrupt is used by the PCIe devices to signal the host to re-establish power and reference clocks while waking from D3Cold/L2 state.

This is based on the DT bindings patch proposed to LKML: https://lore.kernel.org/linux-pci/20230208111645.3863534-2-mmaddireddy@nvidia.com/

In that patch, there were 2 interrupts mentioned: "wake" and "pci", and the latter one was described as "legacy PCI interrupt". But those legacy interrupts are already defined as "INT-{A,B,C,D}" in pci-device.yaml. So I removed that one and just kept "wake".

robherring commented 8 months ago

Can PCI-PCI bridges also generate legacy interrupts?

Mani-Sadhasivam commented 8 months ago

I don't think the bridge itself will trigger legacy interrupts, but PCI-PCI bridge specification has below reference:

Chapter 9, sec 9.1:

Assuming that the bridge is a single function device,
its interrupt pin is required to be connected to INTA# by the PCI Local Bus Specification.
Mani-Sadhasivam commented 8 months ago

@robherring Ping