Non-discoverable devices in PCI devices
summary
Modern PCI endpoints expose multiple MMIO peripherals behind BARs and those peripherals change with FPGA reprogramming, so the practical solution is to attach a DeviceTree node to the PCI function, load a DT fragment carried with the FPGA bitstream, and apply overlays to instantiate platform drivers. Linux already adds generated PCI device DT nodes (Linux 6.6) and fixed address-translation for three-cell mappings, FPGA flows use FPGA image includes DT fragment, but concerns remain about refcounting of DT nodes/properties and that ACPI lacks subsystem descriptions for some devices.
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chapters (9)
- 0:00Introduction to talk
- 1:25Problem with PCI discoverability
- 5:27AMD FPGA PCIe card use case
- 12:30Device tree solution overview
- 16:25ACPI challenges and solutions
- 20:12Dynamic device handling issues
- 23:27Discovering device tree overlays
- 27:03ACPI vs device tree tradeoffs
- 29:00Q&A and closing
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