On Mon, Jan 04, 2021 at 10:57:35PM -0600, Jeremy Linton wrote: > Given that most arm64 platform's PCI implementations needs quirks > to deal with problematic config accesses, this is a good place to > apply a firmware abstraction. The ARM PCI SMMCCC spec details a > standard SMC conduit designed to provide a simple PCI config > accessor. This specification enhances the existing ACPI/PCI > abstraction and expects power, config, etc functionality is handled > by the platform. It also is very explicit that the resulting config > space registers must behave as is specified by the pci specification. > > Lets hook the normal ACPI/PCI config path, and when we detect > missing MADT data, attempt to probe the SMC conduit. If the conduit > exists and responds for the requested segment number (provided by the > ACPI namespace) attach a custom pci_ecam_ops which redirects > all config read/write requests to the firmware. > > This patch is based on the Arm PCI Config space access document @ > https://developer.arm.com/documentation/den0115/latest Why does firmware need to be involved with this at all? Can't we just quirk Linux when these broken designs show up in production? We'll need to modify Linux _anyway_ when the firmware interface isn't implemented correctly... Will
