without semihosting support, use the firmware for a shutdown

Cargo.toml

@@ -65,6 +65,7 @@ udp = ["smoltcp", "smoltcp/socket-udp"]
 trace = []
 vga = []
 common-os = []
+semihosting = []
 
 [dependencies]
 ahash = { version = "0.8", default-features = false }
@@ -127,14 +128,14 @@ qemu-exit = "3.0"
 aarch64 = { version = "0.0", default-features = false }
 arm-gic = { version = "0.1" }
 hermit-dtb = { version = "0.1" }
-semihosting = { version = "0.1", default-features = false }
+semihosting = { version = "0.1" }
 
 [target.'cfg(target_arch = "riscv64")'.dependencies]
 fdt = "0.1"
 riscv = "0.11"
 sbi = "0.2"
 trapframe = "0.9"
-semihosting = { version = "0.1", default-features = false }
+semihosting = { version = "0.1" }
 
 [dev-dependencies]
 float-cmp = "0.9"

src/arch/aarch64/kernel/processor.rs

@@ -117,7 +117,21 @@ pub fn halt() {
 /// Shutdown the system
 pub fn shutdown() -> ! {
 	info!("Shutting down system");
-	semihosting::process::exit(0);
+
+	if cfg!(feature = "semihosting") {
+		semihosting::process::exit(0)
+	} else {
+		unsafe {
+			const PSCI_SYSTEM_OFF: u64 = 0x84000008;
+			// call firmware to shut down the system
+			asm!("hvc #0", in("x0") PSCI_SYSTEM_OFF, options(nomem, nostack));
+
+			// we should never reach this point
+			loop {
+				asm!("wfe", options(nomem, nostack));
+			}
+		}
+	}
 }
 
 #[inline]

src/arch/riscv64/kernel/processor.rs

@@ -229,8 +229,13 @@ pub fn halt() {
 /// Shutdown the system
 pub fn shutdown() -> ! {
 	info!("Shutting down system");
-	//SBI shutdown
-	sbi::legacy::shutdown()
+
+	if cfg!(feature = "semihosting") {
+		semihosting::process::exit(0)
+	} else {
+		// use SBI shutdown
+		sbi::legacy::shutdown()
+	}
 }
 
 pub fn get_timer_ticks() -> u64 {