aarch64: initial psci communication

oro-arch-aarch64/src/boot/mod.rs

@@ -51,5 +51,10 @@ pub unsafe fn boot_primary() -> ! {
 		dbg!("@ {tkn:?}");
 	}
 
+	// XXX DEBUG
+	// Get the PSCI version
+	let version = crate::psci::PsciMethod::Hvc.psci_version();
+	dbg!("PSCI version: {version:?}");
+
 	crate::asm::halt();
 }

oro-arch-aarch64/src/lib.rs

@@ -35,6 +35,7 @@ pub mod asm;
 pub mod boot;
 pub mod mair;
 pub mod mem;
+pub mod psci;
 pub mod reg;
 pub mod sync;
 

oro-arch-aarch64/src/psci.rs

@@ -0,0 +1,58 @@
+//! Provides functionality for interacting with the Power State Coordination Interface (PSCI).
+
+use core::arch::asm;
+
+/// Indicates which PSCI mechanism to use when calling into the firmware.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum PsciMethod {
+	/// Use the HVC (Hypervisor Call) instruction.
+	Hvc,
+	/// Use the SMC (Secure Monitor Call) instruction.
+	Smc,
+}
+
+// NOTE(qix-): I tried to make this DRY with macro_rules!
+// NOTE(qix-): but the `asm!()` macro can't seem to be built up
+// NOTE(qix-): in any meaningful way via macro parameters (namely
+// NOTE(qix-): the `in` clauses). If you can figure out a way to
+// NOTE(qix-): reduce these to simple definitions and codegen the
+// NOTE(qix-): rest, please open a PR. Time spent trying: 2 hours.
+impl PsciMethod {
+	/// Get the version of the PSCI firmware.
+	///
+	/// # Safety
+	/// Traps into a higher exception level. Caller must be in EL1.
+	///
+	/// This function is inherently unsafe as it deals with power levels
+	/// and calls into the OEM's firmware.
+	#[must_use]
+	pub unsafe fn psci_version(&self) -> PsciVersion {
+		let fnid: u32 = 0x8400_0000;
+		let r: u32;
+
+		match self {
+			PsciMethod::Hvc => asm!("hvc 0", in("w0") fnid, lateout("w0") r),
+			PsciMethod::Smc => asm!("smc 0", in("w0") fnid, lateout("w0") r),
+		}
+
+		r.into()
+	}
+}
+
+/// Specifies the version of the PSCI interface.
+#[derive(Clone, Debug)]
+pub struct PsciVersion {
+	/// The major version.
+	pub major: u16,
+	/// The minor version.
+	pub minor: u16,
+}
+
+impl From<u32> for PsciVersion {
+	fn from(v: u32) -> Self {
+		Self {
+			major: ((v >> 16) & 0x7FFF) as u16,
+			minor: v as u16,
+		}
+	}
+}