Implement EEPROM save media.

Fix EEPROM implementation.

agb-tests/tests/test_save_eeprom_512b.rs

@@ -0,0 +1,16 @@
+#![no_std]
+#![no_main]
+#![feature(custom_test_frameworks)]
+#![reexport_test_harness_main = "test_main"]
+#![test_runner(agb::test_runner::test_runner)]
+
+mod save_test_common;
+
+fn save_setup(gba: &mut agb::Gba) {
+    gba.save.init_eeprom_512b();
+}
+
+#[agb::entry]
+fn entry(_gba: agb::Gba) -> ! {
+    loop {}
+}

agb-tests/tests/test_save_eeprom_8k.rs

@@ -0,0 +1,16 @@
+#![no_std]
+#![no_main]
+#![feature(custom_test_frameworks)]
+#![reexport_test_harness_main = "test_main"]
+#![test_runner(agb::test_runner::test_runner)]
+
+mod save_test_common;
+
+fn save_setup(gba: &mut agb::Gba) {
+    gba.save.init_eeprom_8k();
+}
+
+#[agb::entry]
+fn entry(_gba: agb::Gba) -> ! {
+    loop {}
+}

agb/src/dma.rs

@@ -24,3 +24,29 @@ pub(crate) unsafe fn dma_copy16(src: *const u16, dest: *mut u16, count: usize) {
 
     DMA3_CONTROL.set(count as u32 | (1 << 31));
 }
+
+pub(crate) fn dma3_exclusive<R>(f: impl FnOnce() -> R) -> R {
+    const DMA0_CTRL_HI: MemoryMapped<u16> = unsafe { MemoryMapped::new(dma_control_addr(0) + 2) };
+    const DMA1_CTRL_HI: MemoryMapped<u16> = unsafe { MemoryMapped::new(dma_control_addr(1) + 2) };
+    const DMA2_CTRL_HI: MemoryMapped<u16> = unsafe { MemoryMapped::new(dma_control_addr(2) + 2) };
+
+    crate::interrupt::free(|_| {
+        let dma0_ctl = DMA0_CTRL_HI.get();
+        let dma1_ctl = DMA1_CTRL_HI.get();
+        let dma2_ctl = DMA2_CTRL_HI.get();
+        DMA0_CTRL_HI.set(dma0_ctl & !(1 << 15));
+        DMA1_CTRL_HI.set(dma1_ctl & !(1 << 15));
+        DMA2_CTRL_HI.set(dma2_ctl & !(1 << 15));
+
+        // Executes the body of the function with DMAs and IRQs disabled.
+        let ret = f();
+
+        // Continues higher priority DMAs if they were enabled before.
+        DMA0_CTRL_HI.set(dma0_ctl);
+        DMA1_CTRL_HI.set(dma1_ctl);
+        DMA2_CTRL_HI.set(dma2_ctl);
+
+        // returns the return value
+        ret
+    })
+}

agb/src/save/eeprom.rs

@@ -0,0 +1,271 @@
+//! A module containing support for EEPROM.
+//!
+//! EEPROM requires using DMA to issue commands for both reading and writing.
+
+use crate::memory_mapped::MemoryMapped;
+use crate::save::{Error, MediaInfo, MediaType, RawSaveAccess};
+use crate::save::utils::Timeout;
+use core::cmp;
+
+const PORT: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0DFFFF00) };
+const SECTOR_SHIFT: usize = 3;
+const SECTOR_LEN: usize = 1 << SECTOR_SHIFT;
+const SECTOR_MASK: usize = SECTOR_LEN - 1;
+
+/// Sends a DMA command to EEPROM.
+fn dma_send(source: &[u32], ct: usize) {
+    crate::dma::dma3_exclusive(|| unsafe {
+        core::sync::atomic::compiler_fence(core::sync::atomic::Ordering::SeqCst);
+        crate::dma::dma_copy16(source.as_ptr() as *mut u16, 0x0DFFFF00 as *mut u16, ct);
+    });
+}
+
+/// Receives a DMA packet from EEPROM.
+fn dma_receive(source: &mut [u32], ct: usize) {
+    crate::dma::dma3_exclusive(|| unsafe {
+        crate::dma::dma_copy16(0x0DFFFF00 as *mut u16, source.as_ptr() as *mut u16, ct);
+        core::sync::atomic::compiler_fence(core::sync::atomic::Ordering::SeqCst);
+    });
+}
+
+/// Union type to help build/receive commands.
+struct BufferData {
+    idx: usize,
+    data: BufferContents,
+}
+#[repr(align(4))]
+union BufferContents {
+    uninit: (),
+    bits: [u16; 82],
+    words: [u32; 41],
+}
+impl BufferData {
+    fn new() -> Self {
+        BufferData { idx: 0, data: BufferContents { uninit: () } }
+    }
+
+    /// Writes a bit to the output buffer.
+    fn write_bit(&mut self, val: u8) {
+        unsafe {
+            self.data.bits[self.idx] = val as u16;
+            self.idx += 1;
+        }
+    }
+
+    /// Writes a number to the output buffer
+    fn write_num(&mut self, count: usize, num: u32) {
+        for i in 0..count {
+            self.write_bit(((num >> (count - 1 - i)) & 1) as u8);
+        }
+    }
+
+    /// Reads a number from the input buffer.
+    fn read_num(&mut self, off: usize, count: usize) -> u32 {
+        let mut accum = 0;
+        unsafe {
+            for i in 0..count {
+                accum <<= 1;
+                accum |= self.data.bits[off + i] as u32;
+            }
+        }
+        accum
+    }
+
+    /// Receives a number of words into the input buffer.
+    fn receive(&mut self, count: usize) {
+        unsafe {
+            dma_receive(&mut self.data.words, count);
+        }
+    }
+
+    /// Submits the current buffer via DMA.
+    fn submit(&self) {
+        unsafe {
+            dma_send(&self.data.words, self.idx);
+        }
+    }
+}
+
+/// The properties of a given EEPROM type.
+struct EepromProperties {
+    addr_bits: usize,
+    byte_len: usize,
+}
+impl EepromProperties {
+    /// Reads a block from the save media.
+    fn read_sector(&self, word: usize) -> [u8; 8] {
+        // Set address command. The command is two one bits, followed by the
+        // address, followed by a zero bit.
+        //
+        // 512B Command: [1 1|n n n n n n|0]
+        // 8KiB Command: [1 1|n n n n n n n n n n n n n n|0]
+        let mut buf = BufferData::new();
+        buf.write_bit(1);
+        buf.write_bit(1);
+        buf.write_num(self.addr_bits, word as u32);
+        buf.write_bit(0);
+        buf.submit();
+
+        // Receive the buffer data. The EEPROM sends 3 irrelevant bits followed
+        // by 64 data bits.
+        buf.receive(68);
+        let mut out = [0; 8];
+        for i in 0..8 {
+            out[i] = buf.read_num(4 + i * 8, 8) as u8;
+        }
+        out
+    }
+
+    /// Writes a sector directly.
+    fn write_sector_raw(
+        &self, word: usize, block: &[u8], timeout: &mut Timeout,
+    ) -> Result<(), Error> {
+        // Write sector command. The command is a one bit, followed by a
+        // zero bit, followed by the address, followed by 64 bits of data.
+        //
+        // 512B Command: [1 0|n n n n n n|v v v v ...]
+        // 8KiB Command: [1 0|n n n n n n n n n n n n n n|v v v v ...]
+        let mut buf = BufferData::new();
+        buf.write_bit(1);
+        buf.write_bit(0);
+        buf.write_num(self.addr_bits, word as u32);
+        for i in 0..8 {
+            buf.write_num(8, block[i] as u32);
+        }
+        buf.write_bit(0);
+        buf.submit();
+
+        // Wait for the sector to be written for 10 milliseconds.
+        timeout.start();
+        while PORT.get() & 1 != 1 {
+            if timeout.check_timeout_met(10) {
+                return Err(Error::OperationTimedOut);
+            }
+        }
+        Ok(())
+    }
+
+    /// Writes a sector to the EEPROM, keeping any current contents outside the
+    /// buffer's range.
+    fn write_sector_safe(
+        &self, word: usize, data: &[u8], start: usize, timeout: &mut Timeout,
+    ) -> Result<(), Error> {
+        let mut buf = self.read_sector(word);
+        buf[start..start + data.len()].copy_from_slice(data);
+        self.write_sector_raw(word, &buf, timeout)
+    }
+
+    /// Writes a sector to the EEPROM.
+    fn write_sector(
+        &self, word: usize, data: &[u8], start: usize, timeout: &mut Timeout,
+    ) -> Result<(), Error> {
+        if data.len() == 8 && start == 0 {
+            self.write_sector_raw(word, data, timeout)
+        } else {
+            self.write_sector_safe(word, data, start, timeout)
+        }
+    }
+
+    /// Checks whether an offset is in range.
+    fn check_offset(&self, offset: usize, len: usize) -> Result<(), Error> {
+        if offset.checked_add(len).is_none() && (offset + len) > self.byte_len {
+            Err(Error::OutOfBounds)
+        } else {
+            Ok(())
+        }
+    }
+
+    /// Implements EEPROM reads.
+    fn read(&self, mut offset: usize, mut buf: &mut [u8]) -> Result<(), Error> {
+        self.check_offset(offset, buf.len())?;
+        while buf.len() != 0 {
+            let start = offset & SECTOR_MASK;
+            let end_len = cmp::min(SECTOR_LEN - start, buf.len());
+            let sector = self.read_sector(offset >> SECTOR_SHIFT);
+            buf[..end_len].copy_from_slice(&sector[start..start + end_len]);
+            buf = &mut buf[end_len..];
+            offset += end_len;
+        }
+        Ok(())
+    }
+
+    /// Implements EEPROM verifies.
+    fn verify(&self, mut offset: usize, mut buf: &[u8]) -> Result<bool, Error> {
+        self.check_offset(offset, buf.len())?;
+        while buf.len() != 0 {
+            let start = offset & SECTOR_MASK;
+            let end_len = cmp::min(SECTOR_LEN - start, buf.len());
+            if &buf[..end_len] != &self.read_sector(offset >> SECTOR_SHIFT) {
+                return Ok(false);
+            }
+            buf = &buf[end_len..];
+            offset += end_len;
+        }
+        Ok(true)
+    }
+
+    /// Implements EEPROM writes.
+    fn write(&self, mut offset: usize, mut buf: &[u8], timeout: &mut Timeout) -> Result<(), Error> {
+        self.check_offset(offset, buf.len())?;
+        while buf.len() != 0 {
+            let start = offset & SECTOR_MASK;
+            let end_len = cmp::min(SECTOR_LEN - start, buf.len());
+            self.write_sector(offset >> SECTOR_SHIFT, &buf[..end_len], start, timeout)?;
+            buf = &buf[end_len..];
+            offset += end_len;
+        }
+        Ok(())
+    }
+}
+const PROPS_512B: EepromProperties = EepromProperties { addr_bits: 6, byte_len: 512 };
+const PROPS_8K: EepromProperties = EepromProperties { addr_bits: 14, byte_len: 8 * 1024 };
+
+/// The [`RawSaveAccess`] used for 512 byte EEPROM.
+pub struct Eeprom512B;
+impl RawSaveAccess for Eeprom512B {
+    fn info(&self) -> Result<&'static MediaInfo, Error> {
+        Ok(&MediaInfo {
+            media_type: MediaType::Eeprom512B,
+            sector_shift: 3,
+            sector_count: 64,
+            uses_prepare_write: false,
+        })
+    }
+    fn read(&self, offset: usize, buffer: &mut [u8], _: &mut Timeout) -> Result<(), Error> {
+        PROPS_512B.read(offset, buffer)
+    }
+    fn verify(&self, offset: usize, buffer: &[u8], _: &mut Timeout) -> Result<bool, Error> {
+        PROPS_512B.verify(offset, buffer)
+    }
+    fn prepare_write(&self, _: usize, _: usize, _: &mut Timeout) -> Result<(), Error> {
+        Ok(())
+    }
+    fn write(&self, offset: usize, buffer: &[u8], timeout: &mut Timeout) -> Result<(), Error> {
+        PROPS_512B.write(offset, buffer, timeout)
+    }
+}
+
+/// The [`RawSaveAccess`] used for 8 KiB EEPROM.
+pub struct Eeprom8K;
+impl RawSaveAccess for Eeprom8K {
+    fn info(&self) -> Result<&'static MediaInfo, Error> {
+        Ok(&MediaInfo {
+            media_type: MediaType::Eeprom8K,
+            sector_shift: 3,
+            sector_count: 1024,
+            uses_prepare_write: false,
+        })
+    }
+    fn read(&self, offset: usize, buffer: &mut [u8], _: &mut Timeout) -> Result<(), Error> {
+        PROPS_8K.read(offset, buffer)
+    }
+    fn verify(&self, offset: usize, buffer: &[u8], _: &mut Timeout) -> Result<bool, Error> {
+        PROPS_8K.verify(offset, buffer)
+    }
+    fn prepare_write(&self, _: usize, _: usize, _: &mut Timeout) -> Result<(), Error> {
+        Ok(())
+    }
+    fn write(&self, offset: usize, buffer: &[u8], timeout: &mut Timeout) -> Result<(), Error> {
+        PROPS_8K.write(offset, buffer, timeout)
+    }
+}

agb/src/save/mod.rs

@@ -108,7 +108,7 @@ use crate::sync::{Mutex, RawMutexGuard};
 use crate::timer::Timer;
 
 mod asm_utils;
-//pub mod eeprom;
+mod eeprom;
 mod flash;
 mod sram;
 mod utils;
@@ -420,6 +420,36 @@ impl SaveManager {
         set_save_implementation(&flash::FlashAccess);
     }
 
+    /// Declares that the ROM uses 512 bytes EEPROM memory.
+    ///
+    /// EEPROM is generally pretty slow and also very small. It's mainly used in
+    /// Game Paks because it's cheap.
+    ///
+    /// This creates a marker in the ROM that allows emulators to understand what
+    /// save type the Game Pak uses, and configures the save manager to use the
+    /// given save type.
+    ///
+    /// Only one `init_*` function may be called in the lifetime of the program.
+    pub fn init_eeprom_512b(&mut self) {
+        marker::emit_eeprom_marker();
+        set_save_implementation(&eeprom::Eeprom512B);
+    }
+
+    /// Declares that the ROM uses 8 KiB EEPROM memory.
+    ///
+    /// EEPROM is generally pretty slow and also very small. It's mainly used in
+    /// Game Paks because it's cheap.
+    ///
+    /// This creates a marker in the ROM that allows emulators to understand what
+    /// save type the Game Pak uses, and configures the save manager to use the
+    /// given save type.
+    ///
+    /// Only one `init_*` function may be called in the lifetime of the program.
+    pub fn init_eeprom_8k(&mut self) {
+        marker::emit_eeprom_marker();
+        set_save_implementation(&eeprom::Eeprom8K);
+    }
+
     /// Creates a new accessor to the save data.
     ///
     /// You must have initialized the save manager beforehand to use a specific

agb/src/save/utils.rs

@@ -42,6 +42,13 @@ impl Timeout {
         }
     }
 }
+impl Drop for Timeout {
+    fn drop(&mut self) {
+        if let Some(timer) = &mut self.timer {
+            timer.set_enabled(false);
+        }
+    }
+}
 
 pub fn lock_media_access() -> Result<RawMutexGuard<'static>, Error> {
     static LOCK: RawMutex = RawMutex::new();