diff --git a/firmware/ice40-riscv/icE1usb/misc.c b/firmware/ice40-riscv/icE1usb/misc.c
index 4fdd2f5..dca126a 100644
--- a/firmware/ice40-riscv/icE1usb/misc.c
+++ b/firmware/ice40-riscv/icE1usb/misc.c
@@ -56,3 +56,9 @@
 {
 	return misc_regs->e1_tick[0].tx;
 }
+
+void
+reboot(int fw)
+{
+	misc_regs->warmboot = (1 << 2) | (fw << 0);
+}