Implement flash read/erase/program

CHANGELOG.md

@@ -36,6 +36,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Add initial DMA support
 - Allow specification of ADC reference voltage in ADC configuraton structure
 - Added support for hardware-based CRC32 functionality
+- Added flash driver
 
 ### Fixed
 - Stability fixes related to SD card write

src/flash.rs

@@ -0,0 +1,165 @@
+use crate::signature::FlashSize;
+use crate::stm32::FLASH;
+use core::{ptr, slice};
+
+/// Flash erase/program error
+#[derive(Debug, Clone, Copy)]
+pub enum Error {
+    ProgrammingSequence,
+    ProgrammingParallelism,
+    ProgrammingAlignment,
+    WriteProtection,
+    Operation,
+}
+
+impl Error {
+    fn read(flash: &FLASH) -> Option<Self> {
+        let sr = flash.sr.read();
+        if sr.pgserr().bit() {
+            Some(Error::ProgrammingSequence)
+        } else if sr.pgperr().bit() {
+            Some(Error::ProgrammingParallelism)
+        } else if sr.pgaerr().bit() {
+            Some(Error::ProgrammingAlignment)
+        } else if sr.wrperr().bit() {
+            Some(Error::WriteProtection)
+        } else if sr.operr().bit() {
+            Some(Error::Operation)
+        } else {
+            None
+        }
+    }
+}
+
+/// Flash methods implemented for `stm32::FLASH`
+pub trait FlashExt {
+    /// Memory-mapped address
+    fn address(&self) -> usize;
+    /// Size in bytes
+    fn len(&self) -> usize;
+    /// Returns a read-only view of flash memory
+    fn read(&self) -> &[u8] {
+        let ptr = self.address() as *const _;
+        unsafe { slice::from_raw_parts(ptr, self.len()) }
+    }
+    /// Unlock flash for erasing/programming until this method's
+    /// result is dropped
+    fn unlocked(&mut self) -> UnlockedFlash;
+}
+
+impl FlashExt for FLASH {
+    fn address(&self) -> usize {
+        0x0800_0000
+    }
+
+    fn len(&self) -> usize {
+        FlashSize::get().bytes()
+    }
+
+    fn unlocked(&mut self) -> UnlockedFlash {
+        unlock(self);
+        UnlockedFlash { flash: self }
+    }
+}
+
+const PSIZE_X8: u8 = 0b00;
+
+/// Result of `FlashExt::unlocked()`
+pub struct UnlockedFlash<'a> {
+    flash: &'a mut FLASH,
+}
+
+/// Automatically lock flash erase/program when leaving scope
+impl Drop for UnlockedFlash<'_> {
+    fn drop(&mut self) {
+        lock(&self.flash);
+    }
+}
+
+impl UnlockedFlash<'_> {
+    /// Erase a flash sector
+    ///
+    /// Refer to the reference manual to see which sector corresponds
+    /// to which memory address.
+    pub fn erase(&mut self, sector: u8) -> Result<(), Error> {
+        let snb = if sector < 12 { sector } else { sector + 4 };
+
+        #[rustfmt::skip]
+        self.flash.cr.modify(|_, w| unsafe {
+            w
+                // start
+                .strt().set_bit()
+                .psize().bits(PSIZE_X8)
+                // sector number
+                .snb().bits(snb)
+                // sectore erase
+                .ser().set_bit()
+                // no programming
+                .pg().clear_bit()
+        });
+        self.wait_ready();
+        self.ok()
+    }
+
+    /// Program bytes with offset into flash memory,
+    /// aligned to 128-bit rows
+    pub fn program<I>(&mut self, mut offset: usize, mut bytes: I) -> Result<(), Error>
+    where
+        I: Iterator<Item = u8>,
+    {
+        let ptr = self.flash.address() as *mut u8;
+        let mut bytes_written = 1;
+        while bytes_written > 0 {
+            bytes_written = 0;
+            let amount = 16 - (offset % 16);
+
+            #[rustfmt::skip]
+            self.flash.cr.modify(|_, w| unsafe {
+                w
+                    .psize().bits(PSIZE_X8)
+                    // no sector erase
+                    .ser().clear_bit()
+                    // programming
+                    .pg().set_bit()
+            });
+            for _ in 0..amount {
+                match bytes.next() {
+                    Some(byte) => {
+                        unsafe {
+                            ptr::write_volatile(ptr.add(offset), byte);
+                        }
+                        offset += 1;
+                        bytes_written += 1;
+                    }
+                    None => break,
+                }
+            }
+            self.wait_ready();
+            self.ok()?;
+        }
+        self.flash.cr.modify(|_, w| w.pg().clear_bit());
+
+        Ok(())
+    }
+
+    fn ok(&self) -> Result<(), Error> {
+        Error::read(&self.flash).map(Err).unwrap_or(Ok(()))
+    }
+
+    fn wait_ready(&self) {
+        while self.flash.sr.read().bsy().bit() {}
+    }
+}
+
+const UNLOCK_KEY1: u32 = 0x45670123;
+const UNLOCK_KEY2: u32 = 0xCDEF89AB;
+
+fn unlock(flash: &FLASH) {
+    flash.keyr.write(|w| unsafe { w.key().bits(UNLOCK_KEY1) });
+    flash.keyr.write(|w| unsafe { w.key().bits(UNLOCK_KEY2) });
+    assert!(!flash.cr.read().lock().bit())
+}
+
+fn lock(flash: &FLASH) {
+    flash.cr.modify(|_, w| w.lock().set_bit());
+}

src/lib.rs

@@ -159,6 +159,8 @@ pub mod dma;
 #[cfg(feature = "device-selected")]
 pub mod dwt;
 #[cfg(feature = "device-selected")]
+pub mod flash;
+#[cfg(feature = "device-selected")]
 pub mod prelude;
 #[cfg(feature = "device-selected")]
 pub mod pwm;