Re: [PATCH] arm64: PCI: Add quirk for platforms running Windows

Bjorn Helgaas
2023-03-08T18:53:21Z

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@linaro.org>
> ---
> 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.

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.

> [1] https://lore.kernel.org/all/20210527093200.GA16444@lpieralisi/
>
> arch/arm64/kernel/pci.c | 26 ++++++++++++++++++++++++++
> 1 file changed, 26 insertions(+)
>
> diff --git a/arch/arm64/kernel/pci.c b/arch/arm64/kernel/pci.c
> index 2276689b5411..896dbd028b67 100644
> --- a/arch/arm64/kernel/pci.c
> +++ b/arch/arm64/kernel/pci.c
> @@ -109,16 +109,42 @@ int pcibios_root_bridge_prepare(struct pci_host_bridge *bridge)
> return 0;
> }
>
> +#define QCOM_DSDT_QUIRK "Host bridge windows in PNP0A03 _CRS"
> +
> +static struct acpi_platform_list qcom_platlist[] = {
> + /* Thinkpad X13s */
> + { "LENOVO", "SDM8280 ", 0, ACPI_SIG_DSDT, all_versions, QCOM_DSDT_QUIRK },
> + /* Microsoft Surface Pro 9 (5G) and Windows Dev Kit 2023 */
> + { "QCOMM ", "SDM8280 ", 0, ACPI_SIG_DSDT, all_versions, QCOM_DSDT_QUIRK },
> + /* Microsoft Surface Pro X */
> + { "QCOMM ", "SDM8180 ", 0, ACPI_SIG_DSDT, all_versions, QCOM_DSDT_QUIRK },
> + { }
> +};
> +
> static int pci_acpi_root_prepare_resources(struct acpi_pci_root_info *ci)
> {
> struct resource_entry *entry, *tmp;
> int status;
> + int idx;
>
> status = acpi_pci_probe_root_resources(ci);
> +
> + /*
> + * Most arm64 platforms that do not run Windows describe host bridge
> + * registers in PNP0A03 _CRS resources, but some like Qualcomm
> + * Snapdragon Windows laptops describe host bridge windows in there.
> + * We do not want to destroy the resources for these platforms.
> + */
> + idx = acpi_match_platform_list(qcom_platlist);
> + if (idx >= 0)
> + goto done;
> +
> resource_list_for_each_entry_safe(entry, tmp, &ci->resources) {
> if (!(entry->res->flags & IORESOURCE_WINDOW))
> resource_list_destroy_entry(entry);
> }
> +
> +done:
> return status;
> }
>
> --
> 2.17.1
>