5 files changed, 237 insertions, 1 deletions

diff --git a/embassy-stm32/src/flash/f4.rs b/embassy-stm32/src/flash/f4.rs
new file mode 100644
index 000000000..0afa9e829
--- /dev/null
+++ b/embassy-stm32/src/flash/f4.rs
@@ -0,0 +1,175 @@
+use core::convert::TryInto;
+use core::ptr::write_volatile;
+
+use atomic_polyfill::{fence, Ordering};
+
+use super::{ERASE_SIZE, FLASH_BASE, FLASH_SIZE};
+use crate::flash::Error;
+use crate::pac;
+
+// Only available on some devices
+const SECOND_BANK_OFFSET: usize = FLASH_SIZE / 2;
+const SECOND_BANK_SECTOR_START: u32 = 12;
+
+unsafe fn is_dual_bank() -> bool {
+    match FLASH_SIZE / 1024 {
+        // 1 MB devices depend on configuration
+        1024 => {
+            if cfg!(any(
+                feature = "stm32f427",
+                feature = "stm32f429",
+                feature = "stm32f437",
+                feature = "stm32f439",
+                feature = "stm32f469",
+                feature = "stm32f479",
+            )) {
+                pac::FLASH.optcr().read().db1m()
+            } else {
+                false
+            }
+        }
+        // 2 MB devices are always dual bank
+        2048 => true,
+        // All other devices are single bank
+        _ => false,
+    }
+}
+
+pub(crate) unsafe fn lock() {
+    pac::FLASH.cr().modify(|w| w.set_lock(true));
+}
+
+pub(crate) unsafe fn unlock() {
+    pac::FLASH.keyr().write(|w| w.set_key(0x4567_0123));
+    pac::FLASH.keyr().write(|w| w.set_key(0xCDEF_89AB));
+}
+
+pub(crate) unsafe fn blocking_write(offset: u32, buf: &[u8]) -> Result<(), Error> {
+    pac::FLASH.cr().write(|w| {
+        w.set_pg(true);
+        w.set_psize(pac::flash::vals::Psize::PSIZE32);
+    });
+
+    let ret = {
+        let mut ret: Result<(), Error> = Ok(());
+        let mut offset = offset;
+        for chunk in buf.chunks(super::WRITE_SIZE) {
+            for val in chunk.chunks(4) {
+                write_volatile(offset as *mut u32, u32::from_le_bytes(val[0..4].try_into().unwrap()));
+                offset += val.len() as u32;
+
+                // prevents parallelism errors
+                fence(Ordering::SeqCst);
+            }
+
+            ret = blocking_wait_ready();
+            if ret.is_err() {
+                break;
+            }
+        }
+        ret
+    };
+
+    pac::FLASH.cr().write(|w| w.set_pg(false));
+
+    ret
+}
+
+unsafe fn get_sector(addr: u32) -> u8 {
+    let offset = addr - FLASH_BASE as u32;
+
+    let sector = if is_dual_bank() {
+        let bank = offset / SECOND_BANK_OFFSET as u32;
+        let offset_in_bank = offset % SECOND_BANK_OFFSET as u32;
+
+        let sector_in_bank = if offset_in_bank >= ERASE_SIZE as u32 / 2 {
+            4 + offset_in_bank / ERASE_SIZE as u32
+        } else {
+            offset_in_bank / (ERASE_SIZE as u32 / 8)
+        };
+
+        if bank == 1 {
+            SECOND_BANK_SECTOR_START + sector_in_bank
+        } else {
+            sector_in_bank
+        }
+    } else {
+        if offset >= ERASE_SIZE as u32 / 2 {
+            4 + offset / ERASE_SIZE as u32
+        } else {
+            offset / (ERASE_SIZE as u32 / 8)
+        }
+    };
+
+    sector as u8
+}
+
+pub(crate) unsafe fn blocking_erase(from: u32, to: u32) -> Result<(), Error> {
+    let start_sector = get_sector(from);
+    let end_sector = get_sector(to);
+
+    for sector in start_sector..end_sector {
+        let ret = erase_sector(sector as u8);
+        if ret.is_err() {
+            return ret;
+        }
+    }
+
+    Ok(())
+}
+
+unsafe fn erase_sector(sector: u8) -> Result<(), Error> {
+    let bank = (sector >= SECOND_BANK_SECTOR_START) as u8;
+    let snb = (bank << 4) + (sector % SECOND_BANK_SECTOR_START as u8);
+
+    pac::FLASH.cr().modify(|w| {
+        w.set_ser(true);
+        w.set_snb(snb)
+    });
+
+    pac::FLASH.cr().modify(|w| {
+        w.set_strt(true);
+    });
+
+    let ret: Result<(), Error> = blocking_wait_ready();
+
+    clear_all_err();
+
+    ret
+}
+
+pub(crate) unsafe fn clear_all_err() {
+    pac::FLASH.sr().write(|w| {
+        w.set_pgserr(true);
+        w.set_pgperr(true);
+        w.set_pgaerr(true);
+        w.set_wrperr(true);
+        w.set_eop(true);
+    });
+}
+
+pub(crate) unsafe fn blocking_wait_ready() -> Result<(), Error> {
+    loop {
+        let sr = pac::FLASH.sr().read();
+
+        if !sr.bsy() {
+            if sr.pgserr() {
+                return Err(Error::Seq);
+            }
+
+            if sr.pgperr() {
+                return Err(Error::Parallelism);
+            }
+
+            if sr.pgaerr() {
+                return Err(Error::Unaligned);
+            }
+
+            if sr.wrperr() {
+                return Err(Error::Protected);
+            }
+
+            return Ok(());
+        }
+    }
+}
diff --git a/embassy-stm32/src/flash/mod.rs b/embassy-stm32/src/flash/mod.rs
index 31ca243a6..59ca59f65 100644
--- a/embassy-stm32/src/flash/mod.rs
+++ b/embassy-stm32/src/flash/mod.rs
@@ -10,6 +10,7 @@ const FLASH_END: usize = FLASH_BASE + FLASH_SIZE;
 
 #[cfg_attr(any(flash_wl, flash_wb, flash_l0, flash_l1, flash_l4), path = "l.rs")]
 #[cfg_attr(flash_f3, path = "f3.rs")]
+#[cfg_attr(flash_f4, path = "f4.rs")]
 #[cfg_attr(flash_f7, path = "f7.rs")]
 #[cfg_attr(flash_h7, path = "h7.rs")]
 mod family;
diff --git a/embassy-stm32/src/lib.rs b/embassy-stm32/src/lib.rs
index 7be0c77ea..8b8168589 100644
--- a/embassy-stm32/src/lib.rs
+++ b/embassy-stm32/src/lib.rs
@@ -39,7 +39,9 @@ pub mod i2c;
 
 #[cfg(crc)]
 pub mod crc;
-#[cfg(any(flash_l0, flash_l1, flash_wl, flash_wb, flash_l4, flash_f3, flash_f7, flash_h7))]
+#[cfg(any(
+    flash_l0, flash_l1, flash_wl, flash_wb, flash_l4, flash_f3, flash_f4, flash_f7, flash_h7
+))]
 pub mod flash;
 pub mod pwm;
 #[cfg(rng)]
diff --git a/examples/stm32f4/Cargo.toml b/examples/stm32f4/Cargo.toml
index de33ffad8..100c0e608 100644
--- a/examples/stm32f4/Cargo.toml
+++ b/examples/stm32f4/Cargo.toml
@@ -19,6 +19,7 @@ panic-probe = { version = "0.3", features = ["print-defmt"] }
 futures = { version = "0.3.17", default-features = false, features = ["async-await"] }
 heapless = { version = "0.7.5", default-features = false }
 nb = "1.0.0"
+embedded-storage = "0.3.0"
 
 usb-device = "0.2"
 usbd-serial = "0.1.1"
diff --git a/examples/stm32f4/src/bin/flash.rs b/examples/stm32f4/src/bin/flash.rs
new file mode 100644
index 000000000..b531d6f13
--- /dev/null
+++ b/examples/stm32f4/src/bin/flash.rs
@@ -0,0 +1,57 @@
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+use defmt::{info, unwrap};
+use embassy::executor::Spawner;
+use embassy::time::{Duration, Timer};
+use embassy_stm32::flash::Flash;
+use embassy_stm32::Peripherals;
+use embedded_storage::nor_flash::{NorFlash, ReadNorFlash};
+use {defmt_rtt as _, panic_probe as _};
+
+#[embassy::main]
+async fn main(_spawner: Spawner, p: Peripherals) {
+    info!("Hello Flash!");
+
+    const ADDR: u32 = 0x10_0000;
+
+    // wait a bit before accessing the flash
+    Timer::after(Duration::from_millis(300)).await;
+
+    let mut f = Flash::unlock(p.FLASH);
+
+    info!("Reading...");
+    let mut buf = [0u8; 32];
+    unwrap!(f.read(ADDR, &mut buf));
+    info!("Read: {=[u8]:x}", buf);
+
+    info!("Erasing...");
+    unwrap!(f.erase(ADDR, ADDR + 128 * 1024));
+
+    info!("Reading...");
+    let mut buf = [0u8; 32];
+    unwrap!(f.read(ADDR, &mut buf));
+    info!("Read after erase: {=[u8]:x}", buf);
+
+    info!("Writing...");
+    unwrap!(f.write(
+        ADDR,
+        &[
+            1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29,
+            30, 31, 32
+        ]
+    ));
+
+    info!("Reading...");
+    let mut buf = [0u8; 32];
+    unwrap!(f.read(ADDR, &mut buf));
+    info!("Read: {=[u8]:x}", buf);
+    assert_eq!(
+        &buf[..],
+        &[
+            1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29,
+            30, 31, 32
+        ]
+    );
+}