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From:   Maximilian Luz <luzmaximilian@gmail.com>
To:     Bjorn Helgaas <bhelgaas@google.com>
Cc:     Maximilian Luz <luzmaximilian@gmail.com>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Len Brown <lenb@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>, linux-pci@vger.kernel.org,
        linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org
Subject: [RFC PATCH] Revert "arm64: PCI: Exclude ACPI "consumer" resources from host bridge windows"
Date:   Tue, 11 May 2021 01:40:20 +0200
Message-Id: <20210510234020.1330087-1-luzmaximilian@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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 */
    }

meaning that the memory resources aren't (explicitly) defined as
"producers", i.e. host bridge windows.

Commit 8fd4391ee717 ("arm64: PCI: Exclude ACPI "consumer" resources from
host bridge windows") introduced a check that removes such resources,
causing BAR allocation failures 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.

On x86 we already skip the check for producer/window due to some history
with negligent firmware. It seems that Microsoft is intent on continuing
that history on their ARM devices, so let's drop that check here too.

Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
---

Please note: I am not sure if this is the right way to fix that, e.g. I
don't know if any additional checks like on IA64 or x86 might be
required instead, or if this might break things on other devices. So
please consider this more as a bug report rather than a fix.

Apologies for the re-send, I seem to have unintentionally added a blank
line before the subject.

---
 arch/arm64/kernel/pci.c | 14 --------------
 1 file changed, 14 deletions(-)

diff --git a/arch/arm64/kernel/pci.c b/arch/arm64/kernel/pci.c
index 1006ed2d7c60..80f87fe0a2b8 100644
--- a/arch/arm64/kernel/pci.c
+++ b/arch/arm64/kernel/pci.c
@@ -94,19 +94,6 @@ int pcibios_root_bridge_prepare(struct pci_host_bridge *bridge)
 	return 0;
 }
 
-static int pci_acpi_root_prepare_resources(struct acpi_pci_root_info *ci)
-{
-	struct resource_entry *entry, *tmp;
-	int status;
-
-	status = acpi_pci_probe_root_resources(ci);
-	resource_list_for_each_entry_safe(entry, tmp, &ci->resources) {
-		if (!(entry->res->flags & IORESOURCE_WINDOW))
-			resource_list_destroy_entry(entry);
-	}
-	return status;
-}
-
 /*
  * Lookup the bus range for the domain in MCFG, and set up config space
  * mapping.
@@ -184,7 +171,6 @@ struct pci_bus *pci_acpi_scan_root(struct acpi_pci_root *root)
 	}
 
 	root_ops->release_info = pci_acpi_generic_release_info;
-	root_ops->prepare_resources = pci_acpi_root_prepare_resources;
 	root_ops->pci_ops = (struct pci_ops *)&ri->cfg->ops->pci_ops;
 	bus = acpi_pci_root_create(root, root_ops, &ri->common, ri->cfg);
 	if (!bus)
-- 
2.31.1