Minor cleanup

tetros/src/lib.rs

@@ -4,6 +4,7 @@
 #![feature(abi_x86_interrupt)]
 #![allow(internal_features)]
 
+use core::arch::asm;
 use lazy_static::lazy_static;
 use rand::{rngs::SmallRng, SeedableRng};
 use spin::Mutex;
@@ -25,6 +26,7 @@ pub(crate) static PIC: Mutex<PICDriver> = Mutex::new(PICDriver::new(32, 32 + 8))
 pub(crate) static TICK_COUNTER: Mutex<u32> = Mutex::new(0);
 pub(crate) static BOARD: Mutex<TetrisBoard> = Mutex::new(TetrisBoard::new());
 pub(crate) static FALLING: Mutex<Option<FallingTetromino>> = Mutex::new(None);
+pub(crate) static RUN_TICKS: Mutex<bool> = Mutex::new(false);
 
 lazy_static! {
 	static ref RNG: Mutex<SmallRng> = Mutex::new(SmallRng::seed_from_u64(1337));
@@ -44,30 +46,23 @@ extern "x86-interrupt" fn divide_handler(stack_frame: InterruptStackFrame) {
 }
 
 extern "x86-interrupt" fn timer_handler(_stack_frame: InterruptStackFrame) {
-	let mut t = TICK_COUNTER.lock();
+	if !*RUN_TICKS.lock() {
-	*t = (*t).wrapping_add(1);
+		PIC.lock().send_eoi(32);
-	drop(t);
+		return;
+	}
 
-	tick();
+	// Step tick counter
+	let t = {
+		let mut t = TICK_COUNTER.lock();
+		*t = (*t).wrapping_add(1);
+		*t
+	};
 
-	PIC.lock().send_eoi(32);
-}
-
-extern "x86-interrupt" fn double_fault_handler(
-	stack_frame: InterruptStackFrame,
-	error_code: u32,
-) -> ! {
-	panic!("DOUBLE FAULT (err = 0x{error_code:x}\n{:#?}", stack_frame);
-}
-
-fn tick() {
 	let mut v = VGA.lock();
-	let t = *TICK_COUNTER.lock();
 	let mut board = BOARD.lock();
 	let mut fall = FALLING.lock();
 
 	v.swap();
-
 	board.draw(&mut v, fall.as_ref());
 
 	if let Some(fall_inner) = fall.as_mut() {
@@ -84,6 +79,15 @@ fn tick() {
 	} else {
 		*fall = Some(FallingTetromino::random(5, 1))
 	}
+
+	PIC.lock().send_eoi(32);
+}
+
+extern "x86-interrupt" fn double_fault_handler(
+	stack_frame: InterruptStackFrame,
+	error_code: u32,
+) -> ! {
+	panic!("DOUBLE FAULT (err = 0x{error_code:x}\n{:#?}", stack_frame);
 }
 
 #[no_mangle]
@@ -118,16 +122,11 @@ pub unsafe extern "C" fn start(
 		pic.init();
 	}
 
-	// Clear screen
+	*RUN_TICKS.lock() = true;
-	let mut v = VGA.lock();
-	let board = BOARD.lock();
 
-	board.draw(&mut v, None);
+	// Do-nothing loop,
-	v.swap();
+	// frames are driven by interrupts
-
+	loop {
-	// Important to drop these, or tick() will deadlock
+		asm!("hlt")
-	drop(v);
+	}
-	drop(board);
-
-	loop {}
 }