+ 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.
Shawn
