On Tue, Jan 23, 2024 at 04:18:34PM -0700, Matthew W Carlis wrote: > Hello again! I'm glad that I'm not the only person with a little > confusion about the FW ECN regarding DPC/EDR. I would argue that DPC > wasn't tied to EDR & shouldn't have been because DPC was added in > PCI Base Spec Rev 3.1 in 2014, but there wasn't an EDR ECN till > ~2020. Anyway, that's the way it goes.. It does involve several different specs (PCIe Base for the DPC hardware feature, ACPI for the OS/firmware EDR interface, PCI Firmware for the EDR support and DPC ownership negotiation), so maybe that helps explain the muddle. > I don't want to burden the kernel with making some impossible boot > time decision here. Perhaps most of the machines in the world using > DPC will soon use EDR/SFI etc. My use cases are a bit out of the > ordinary & the ACPI specifications don't seem to have given us a > mechanism for the kernel to conclude it can use DPC without EDR > support... I don't know anything about SFI and I don't see any required connection between DPC/EDR/SFI in the PCI Firmware spec. The PCI Firmware spec requires ACPI OSes to support EDR if they want to use DPC. But I don't know that the firmware is required to actually implement the EDR functionality. Non-ACPI OSes are presumed to own DPC and all other PCIe hardware features, and I don't think EDR would be in the picture since it's an ACPI thing. > Shall I submit a patch removing CONFIG_PCIE_EDR? Perhaps the > exercise would inform me about whether its code should be in > CONFIG_PCIE_DPC or CONFIG_ACPI. That would be great! I would say CONFIG_PCIE_EDR should go away and edr.c should only be compiled if CONFIG_PCIE_DPC=y and CONFIG_ACPI=y. Bjorn
