1 files changed, 55 insertions, 0 deletions
diff --git a/drivers/acpi/reboot.c b/drivers/acpi/reboot.c
new file mode 100644
index 000000000..6fa9c2a4c
--- /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;
+	}
+}