feat(serial): support disconnected Joybus configuration and local registers

crates/gba-core/tests/serial_joybus.rs

@@ -0,0 +1,142 @@
+//! Original disconnected Joybus probes. No external commands or linked transfers.
+use gba_core::{
+    cpu::Cpu,
+    dma::DMA_BASE,
+    io::{HALTCNT, IE, IF, IME, JOYCNT, JOYSTAT, JOY_RECV, JOY_TRANS, RCNT, SIOCNT, SIODATA8},
+    machine::{Machine, StepKind},
+    memory::{Memory, MemoryError, ROM_START},
+};
+
+fn memory() -> Memory {
+    Memory::new(0xeaff_fffe_u32.to_le_bytes().to_vec()).unwrap()
+}
+
+#[test]
+fn local_register_masks_do_not_fabricate_remote_events_in_any_mode() {
+    let mut bus = memory();
+    for mode in [0, 0x8000, 0xc000, 0xc100, 0x4100] {
+        bus.write16(RCNT, mode).unwrap();
+        for value in 0..=255 {
+            bus.write16(JOYCNT, 0xff00 | value).unwrap();
+            bus.write16(JOYSTAT, 0xff00 | value).unwrap();
+            assert_eq!(bus.read16(JOYCNT).unwrap(), value & 0x40);
+            assert_eq!(bus.read16(JOYSTAT).unwrap(), value & 0x30);
+            bus.write8(JOYCNT + 1, 0xff).unwrap();
+            bus.write8(JOYSTAT + 1, 0xff).unwrap();
+            assert_eq!(bus.read16(JOYCNT).unwrap(), value & 0x40);
+            assert_eq!(bus.read16(JOYSTAT).unwrap(), value & 0x30);
+        }
+        bus.advance_cycles(1000000);
+        assert_eq!(bus.read16(IF).unwrap(), 0);
+    }
+}
+
+#[test]
+fn data_lanes_retain_words_and_transmit_writes_set_pending_not_completion() {
+    for mode in [0, 0x8000, 0xc000] {
+        for base in [JOY_RECV, JOY_TRANS] {
+            let mut bus = memory();
+            bus.write16(RCNT, mode).unwrap();
+            for lane in 0..4 {
+                bus.write8(base + lane, (0x12 + lane * 0x22) as u8).unwrap();
+            }
+            assert_eq!(bus.read32(base).unwrap(), 0x78563412);
+            bus.write16(base + 2, 0xabcd).unwrap();
+            assert_eq!(bus.read32(base).unwrap(), 0xabcd3412);
+            bus.write32(base, 0x98765432).unwrap();
+            assert_eq!(bus.read16(base).unwrap(), 0x5432);
+            assert_eq!(bus.read16(base + 2).unwrap(), 0x9876);
+            let pending = if base == JOY_TRANS { 2 } else { 0 };
+            assert_eq!(bus.read16(JOYSTAT).unwrap(), pending);
+            bus.write16(JOYSTAT, 0xffff).unwrap();
+            assert_eq!(bus.read16(JOYSTAT).unwrap(), pending | 0x30);
+            bus.write16(JOYSTAT, 0).unwrap(); // Software cannot clear transmit pending.
+            bus.write16(JOYCNT, 0x47).unwrap();
+            bus.read32(JOY_RECV).unwrap();
+            bus.advance_cycles(1000000);
+            assert_eq!(bus.read16(JOYSTAT).unwrap(), pending);
+            assert_eq!(bus.read16(JOYCNT).unwrap(), 0x40);
+            assert_eq!(bus.read16(IF).unwrap(), 0);
+            bus.write16(RCNT, 0x8000).unwrap();
+            bus.write16(RCNT, 0xc100).unwrap();
+            assert_eq!(bus.read32(base).unwrap(), 0x98765432);
+            assert_eq!(bus.read16(JOYSTAT).unwrap(), pending);
+        }
+    }
+    // Writing zero also makes a reply available; zero is not a reset strobe.
+    let mut bus = memory();
+    bus.write8(JOY_TRANS + 3, 0).unwrap();
+    assert_eq!(bus.read16(JOYSTAT).unwrap(), 2);
+}
+
+#[test]
+fn joybus_does_not_run_normal_clocks_or_wake_halt_or_stop() {
+    for stop in [false, true] {
+        let mut bus = memory();
+        bus.write16(RCNT, 0xc100).unwrap(); // Bit 8 is inactive, not a GPIO IRQ enable.
+        bus.write16(SIOCNT, 0x4083).unwrap(); // Unused in Joybus, even with internal start retained.
+        bus.write8(SIODATA8, 0x12).unwrap();
+        bus.write16(JOYCNT, 0x40).unwrap();
+        bus.write32(JOY_TRANS, 0xaabbccdd).unwrap();
+        bus.write16(IE, 0x80).unwrap();
+        bus.write16(IME, 1).unwrap();
+        bus.write8(HALTCNT, if stop { 0x80 } else { 0 }).unwrap();
+        bus.advance_cycles(1000000);
+        assert_eq!(bus.stopped(), stop);
+        assert_eq!(bus.halted(), !stop);
+        assert_eq!(bus.read8(SIODATA8).unwrap(), 0x12);
+        assert_eq!(bus.read16(SIOCNT).unwrap(), 0x4083);
+        assert_eq!(bus.read16(JOYCNT).unwrap(), 0x40);
+        assert_eq!(bus.read16(JOYSTAT).unwrap(), 2);
+        assert_eq!(bus.read16(IF).unwrap(), 0);
+        assert_eq!(bus.read8(RCNT), Err(MemoryError::Unmapped(RCNT)));
+    }
+}
+
+#[test]
+fn live_normal_transfer_requires_completion_or_explicit_cancellation_before_joybus() {
+    let mut bus = memory();
+    bus.write16(SIOCNT, 0x4083).unwrap();
+    for elapsed in [0, 8] {
+        bus.advance_cycles(elapsed);
+        let error = bus.write16(RCNT, 0xc100).unwrap_err();
+        assert!(error.to_string().contains("serial reconfiguration"));
+        assert_eq!(bus.write16(RCNT, 0xc100), Err(error));
+        assert_eq!(bus.read8(RCNT + 1).unwrap(), 0);
+    }
+    bus.write16(SIOCNT, 0).unwrap();
+    bus.write16(RCNT, 0xc100).unwrap();
+    bus.advance_cycles(1000000);
+    assert_eq!(bus.read16(IF).unwrap(), 0);
+}
+
+#[test]
+fn joy_control_and_status_word_padding_fail_without_partial_side_effects() {
+    let mut bus = memory();
+    for address in [JOYCNT, JOYSTAT] {
+        assert_eq!(
+            bus.write32(address, u32::MAX),
+            Err(MemoryError::Unmapped(address + 2))
+        );
+        assert_eq!(bus.read32(address), Err(MemoryError::Unmapped(address + 2)));
+        assert_eq!(bus.read16(address).unwrap(), 0);
+    }
+}
+
+#[test]
+fn dma_transmit_write_has_only_dma_completion_irq() {
+    let mut bus = memory();
+    bus.write16(RCNT, 0xc000).unwrap();
+    bus.write16(JOYCNT, 0x40).unwrap();
+    bus.write32(0x02000000, 0x12345678).unwrap();
+    bus.write32(DMA_BASE, 0x02000000).unwrap();
+    bus.write32(DMA_BASE + 4, JOY_TRANS).unwrap();
+    bus.write32(DMA_BASE + 8, 0xc4000001).unwrap();
+    let mut machine = Machine::new(Cpu::new(ROM_START), bus);
+    assert_eq!(machine.step().unwrap(), StepKind::Dma { channel: 0 });
+    assert_eq!(machine.memory().read32(JOY_TRANS).unwrap(), 0x12345678);
+    assert_eq!(machine.memory().read16(JOYSTAT).unwrap(), 2);
+    assert_eq!(machine.memory().read16(IF).unwrap(), 0x100);
+    machine.memory_mut().advance_cycles(1000000);
+    assert_eq!(machine.memory().read16(IF).unwrap(), 0x100);
+}