v4.19.13 snapshot.
diff --git a/drivers/acpi/reboot.c b/drivers/acpi/reboot.c
new file mode 100644
index 0000000..6fa9c2a
--- /dev/null
+++ b/drivers/acpi/reboot.c
@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/pci.h>
+#include <linux/acpi.h>
+#include <acpi/reboot.h>
+
+void acpi_reboot(void)
+{
+ struct acpi_generic_address *rr;
+ struct pci_bus *bus0;
+ unsigned int devfn;
+ u8 reset_value;
+
+ if (acpi_disabled)
+ return;
+
+ rr = &acpi_gbl_FADT.reset_register;
+
+ /* ACPI reset register was only introduced with v2 of the FADT */
+
+ if (acpi_gbl_FADT.header.revision < 2)
+ return;
+
+ /* Is the reset register supported? The spec says we should be
+ * checking the bit width and bit offset, but Windows ignores
+ * these fields */
+ if (!(acpi_gbl_FADT.flags & ACPI_FADT_RESET_REGISTER))
+ return;
+
+ reset_value = acpi_gbl_FADT.reset_value;
+
+ /* The reset register can only exist in I/O, Memory or PCI config space
+ * on a device on bus 0. */
+ switch (rr->space_id) {
+ case ACPI_ADR_SPACE_PCI_CONFIG:
+ /* The reset register can only live on bus 0. */
+ bus0 = pci_find_bus(0, 0);
+ if (!bus0)
+ return;
+ /* Form PCI device/function pair. */
+ devfn = PCI_DEVFN((rr->address >> 32) & 0xffff,
+ (rr->address >> 16) & 0xffff);
+ printk(KERN_DEBUG "Resetting with ACPI PCI RESET_REG.\n");
+ /* Write the value that resets us. */
+ pci_bus_write_config_byte(bus0, devfn,
+ (rr->address & 0xffff), reset_value);
+ break;
+
+ case ACPI_ADR_SPACE_SYSTEM_MEMORY:
+ case ACPI_ADR_SPACE_SYSTEM_IO:
+ printk(KERN_DEBUG "ACPI MEMORY or I/O RESET_REG.\n");
+ acpi_reset();
+ break;
+ }
+}