Subject: [PATCH 4/4] arm64: pci: acpi: Preserve PCI resources configuration when asked by ACPI

From: Benjamin Herrenschmidt <[email-masked]>
Date: Sat, 15 Jun 2019 10:23:59 +1000

When _DSM #5 returns 0 for a host bridge, we need to claim the existing
resources rather than reassign everything.

Signed-off-by: Benjamin Herrenschmidt <[email-masked]>
---
 arch/arm64/kernel/pci.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/arm64/kernel/pci.c b/arch/arm64/kernel/pci.c
index 1419b1b4e9b9..a2c608a3fc41 100644
--- a/arch/arm64/kernel/pci.c
+++ b/arch/arm64/kernel/pci.c
@@ -168,6 +168,7 @@ struct pci_bus *pci_acpi_scan_root(struct acpi_pci_root *root)
 	struct acpi_pci_generic_root_info *ri;
 	struct pci_bus *bus, *child;
 	struct acpi_pci_root_ops *root_ops;
+	struct pci_host_bridge *hb;
 
 	ri = kzalloc(sizeof(*ri), GFP_KERNEL);
 	if (!ri)
@@ -193,6 +194,16 @@ struct pci_bus *pci_acpi_scan_root(struct acpi_pci_root *root)
 	if (!bus)
 		return NULL;
 
+	hb = pci_find_host_bridge(bus);
+
+	/* If ACPI tells us to preserve the resource configuration, claim now */
+	if (hb->preserve_config)
+		pci_bus_claim_resources(bus);
+
+	/*
+	 * Assign whatever was left unassigned. If we didn't claim above, this will
+	 * reassign everything.
+	 */
 	pci_assign_unassigned_root_bus_resources(bus);
 
 	list_for_each_entry(child, &bus->children, node)
-- 
2.17.1

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