On Wed, May 23, 2018 at 03:10:39PM -0400, Sinan Kaya wrote: > > If that doesn't work or you'd rather brute-force it, you could try > > doing something like "pci=earlydump". This is currently only > > implemented for x86, so it would be some work to implement something > > similar for arm64. It would be a nice upstream addition if you *did* > > implement it. > > > > In the earlydump output I would be looking for clues about the power > > state of 03:00.0 to try to figure out if the bootloader left it powered > > off or if Linux is doing something to turn it off. > > > > Is it really possible to implement a generic version of this? > > PCI on ARM64 is not really unified. There are several host bridge drivers > for different types of access. > > If we limit the functionality to ACPI, the answer is still maybe if we > can pass the base address of the MMCONFIG region. > > All products use a different MMCONFIG region. On x86, early dump is implemented off to the side, outside the PCI core, and it takes advantage of arch-specific knowledge about ways to perform config accesses. But I could imagine something in the pci_scan_device() area, where we have the normal config accessors but we haven't yet touched the device. I think we could get 99% of the early dump utility in a completely generic way. There might be a few hand-crafted arch-specific quirks that touch PCI devices even before that point, but those should be pretty rare. Bjorn
