1 files changed, 77 insertions, 0 deletions
diff --git a/arch/x86/pci/legacy.c b/arch/x86/pci/legacy.c
new file mode 100644
index 0000000000..467311b1ee
--- /dev/null
+++ b/arch/x86/pci/legacy.c
@@ -0,0 +1,77 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * legacy.c - traditional, old school PCI bus probing
+ */
+#include <linux/init.h>
+#include <linux/export.h>
+#include <linux/pci.h>
+#include <asm/jailhouse_para.h>
+#include <asm/pci_x86.h>
+
+/*
+ * Discover remaining PCI buses in case there are peer host bridges.
+ * We use the number of last PCI bus provided by the PCI BIOS.
+ */
+static void pcibios_fixup_peer_bridges(void)
+{
+	int n;
+
+	if (pcibios_last_bus <= 0 || pcibios_last_bus > 0xff)
+		return;
+	DBG("PCI: Peer bridge fixup\n");
+
+	for (n=0; n <= pcibios_last_bus; n++)
+		pcibios_scan_specific_bus(n);
+}
+
+int __init pci_legacy_init(void)
+{
+	if (!raw_pci_ops)
+		return 1;
+
+	pr_info("PCI: Probing PCI hardware\n");
+	pcibios_scan_root(0);
+	return 0;
+}
+
+void pcibios_scan_specific_bus(int busn)
+{
+	int stride = jailhouse_paravirt() ? 1 : 8;
+	int devfn;
+	u32 l;
+
+	if (pci_find_bus(0, busn))
+		return;
+
+	for (devfn = 0; devfn < 256; devfn += stride) {
+		if (!raw_pci_read(0, busn, devfn, PCI_VENDOR_ID, 2, &l) &&
+		    l != 0x0000 && l != 0xffff) {
+			DBG("Found device at %02x:%02x [%04x]\n", busn, devfn, l);
+			pr_info("PCI: Discovered peer bus %02x\n", busn);
+			pcibios_scan_root(busn);
+			return;
+		}
+	}
+}
+EXPORT_SYMBOL_GPL(pcibios_scan_specific_bus);
+
+static int __init pci_subsys_init(void)
+{
+	/*
+	 * The init function returns an non zero value when
+	 * pci_legacy_init should be invoked.
+	 */
+	if (x86_init.pci.init()) {
+		if (pci_legacy_init()) {
+			pr_info("PCI: System does not support PCI\n");
+			return -ENODEV;
+		}
+	}
+
+	pcibios_fixup_peer_bridges();
+	x86_init.pci.init_irq();
+	pcibios_init();
+
+	return 0;
+}
+subsys_initcall(pci_subsys_init);