On Thu, Mar 09, 2023 at 10:52:13AM +0800, Shawn Guo wrote: > + linux-arm-msm and MSM maintainer Bjorn > > On Wed, Mar 08, 2023 at 12:53:10PM -0600, Bjorn Helgaas wrote: > > On Mon, Feb 27, 2023 at 10:12:21AM +0800, Shawn Guo wrote: > > > Commit 8fd4391ee717 ("arm64: PCI: Exclude ACPI "consumer" resources from > > > host bridge windows") introduced a check to remove host bridge register > > > resources for all arm64 platforms, with the assumption that the PNP0A03 > > > _CRS resources would always be host bridge registers and never as windows > > > on arm64. > > > > > > The assumption stands true until Qualcomm Snapdragon Windows laptops > > > emerge. These laptops describe host bridge windows in PNP0A03 _CRS > > > resources instead. For example, the Microsoft Surface Pro X has host > > > bridges defined as > > > > > > Name (_HID, EisaId ("PNP0A08") /* PCI Express Bus */) // _HID: Hardware ID > > > Name (_CID, EisaId ("PNP0A03") /* PCI Bus */) // _CID: Compatible ID > > > > > > Method (_CRS, 0, NotSerialized) // _CRS: Current Resource Settings > > > { > > > Name (RBUF, ResourceTemplate () > > > { > > > Memory32Fixed (ReadWrite, > > > 0x60200000, // Address Base > > > 0x01DF0000, // Address Length > > > ) > > > WordBusNumber (ResourceProducer, MinFixed, MaxFixed, PosDecode, > > > 0x0000, // Granularity > > > 0x0000, // Range Minimum > > > 0x0001, // Range Maximum > > > 0x0000, // Translation Offset > > > 0x0002, // Length > > > ,, ) > > > }) > > > Return (RBUF) /* \_SB_.PCI0._CRS.RBUF */ > > > } > > > > > > The Memory32Fixed holds a host bridge window, but it's not properly > > > defined as a "producer" resource. Consequently the resource gets > > > removed by kernel, and the BAR allocation fails later on: > > > > > > [ 0.150731] pci 0002:00:00.0: BAR 14: no space for [mem size 0x00100000] > > > [ 0.150744] pci 0002:00:00.0: BAR 14: failed to assign [mem size 0x00100000] > > > [ 0.150758] pci 0002:01:00.0: BAR 0: no space for [mem size 0x00004000 64bit] > > > [ 0.150769] pci 0002:01:00.0: BAR 0: failed to assign [mem size 0x00004000 64bit] > > > > > > This eventually prevents the PCIe NVME drive from being accessible. > > > > > > Add a quirk for these platforms to avoid the resource being removed. > > > > > > Signed-off-by: Shawn Guo <shawn.guo@xxxxxxxxxx> > > > --- > > > We are running into the issue on more devices than just Surface Pro X > > > now, so trying to sort it out with a quirk as suggested by Lorenzo [1]. > > > > One thing I don't like about this application of quirks is that the > > list of affected platforms is likely to grow, which is an ongoing > > burden for users and developers. > > It's a very reasonable concern. I really hope that Qualcomm will start > thinking about Linux support on these machines in the future not too far > away, so that the list will not grow too long. > > > Can we have a conversation with Qualcomm about how they *intend* this > > to work? Linux is probably doing something wrong (interpreting > > something differently than Windows does), and if we could fix that, we > > have a better chance of future platforms working without quirks. > > Today Qualcomm only ships and cares about Windows on these machines, but > I believe it will change sooner or later. I don't maintain arch/arm64/kernel/pci.c, but my opinion is that we should not pursue quirks like this until we've tried really hard to figure out a generic approach. Bjorn