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-rw-r--r--arch/x86/pci/legacy.c77
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 000000000..467311b1e
--- /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);