Add is_eraseable_range and split write into consecutive parts

embassy-stm32/src/flash/f3.rs

@@ -1,13 +1,13 @@
 use core::convert::TryInto;
-use core::mem::size_of;
 use core::ptr::write_volatile;
 
-use super::FlashRegion;
+use atomic_polyfill::{fence, Ordering};
+
+use super::{FlashRegion, BANK1, WRITE_SIZE};
 use crate::flash::Error;
 use crate::pac;
 
-pub(crate) const MAX_WRITE_SIZE: usize = super::BANK1::WRITE_SIZE;
+const ERASE_SIZE: usize = BANK1::ERASE_SIZE;
-pub(crate) const MAX_ERASE_SIZE: usize = super::BANK1::ERASE_SIZE;
 
 pub(crate) unsafe fn lock() {
     pac::FLASH.cr().modify(|w| w.set_lock(true));
@@ -18,33 +18,35 @@ pub(crate) unsafe fn unlock() {
     pac::FLASH.keyr().write(|w| w.set_fkeyr(0xCDEF_89AB));
 }
 
-pub(crate) unsafe fn blocking_write(first_address: u32, buf: &[u8]) -> Result<(), Error> {
+pub(crate) unsafe fn begin_write() {
-    pac::FLASH.cr().write(|w| w.set_pg(true));
+    assert_eq!(0, WRITE_SIZE % 2);
 
-    let ret = {
+    pac::FLASH.cr().write(|w| w.set_pg(true));
-        let mut ret: Result<(), Error> = Ok(());
+}
-        let mut address = first_address;
+
-        let chunks = buf.chunks_exact(size_of::<u16>());
+pub(crate) unsafe fn end_write() {
-        assert!(chunks.remainder().is_empty());
+    pac::FLASH.cr().write(|w| w.set_pg(false));
-        for chunk in chunks {
+}
+
+pub(crate) unsafe fn blocking_write(start_address: u32, buf: &[u8; WRITE_SIZE]) -> Result<(), Error> {
+    let mut address = start_address;
+    for chunk in buf.chunks(2) {
         write_volatile(address as *mut u16, u16::from_le_bytes(chunk.try_into().unwrap()));
         address += chunk.len() as u32;
 
-            ret = blocking_wait_ready();
+        // prevents parallelism errors
-            if ret.is_err() {
+        fence(Ordering::SeqCst);
-                break;
     }
-        }
-        ret
-    };
 
-    pac::FLASH.cr().write(|w| w.set_pg(false));
+    blocking_wait_ready()
-
-    ret
 }
 
-pub(crate) unsafe fn blocking_erase(from_address: u32, to_address: u32) -> Result<(), Error> {
+pub(crate) fn is_eraseable_range(start_address: u32, end_address: u32) -> bool {
-    for page in (from_address..to_address).step_by(MAX_ERASE_SIZE) {
+    start_address % ERASE_SIZE as u32 == 0 && end_address % ERASE_SIZE as u32 == 0
+}
+
+pub(crate) unsafe fn blocking_erase(start_address: u32, end_address: u32) -> Result<(), Error> {
+    for page in (start_address..end_address).step_by(ERASE_SIZE) {
         pac::FLASH.cr().modify(|w| {
             w.set_per(true);
         });
@@ -71,7 +73,6 @@ pub(crate) unsafe fn blocking_erase(from_address: u32, to_address: u32) -> Resul
             return ret;
         }
     }
-
     Ok(())
 }
 
@@ -89,7 +90,7 @@ pub(crate) unsafe fn clear_all_err() {
     });
 }
 
-pub(crate) unsafe fn blocking_wait_ready() -> Result<(), Error> {
+unsafe fn blocking_wait_ready() -> Result<(), Error> {
     loop {
         let sr = pac::FLASH.sr().read();
 

embassy-stm32/src/flash/f4.rs

@@ -1,23 +1,19 @@
 use core::convert::TryInto;
-use core::mem::size_of;
 use core::ptr::write_volatile;
 use core::sync::atomic::{fence, Ordering};
 
 use embassy_hal_common::stm32::flash::f4::{get_sector, SECOND_BANK_SECTOR_OFFSET};
 
-use super::{FlashRegion, FLASH_SIZE};
+use super::{FLASH_SIZE, WRITE_SIZE};
 use crate::flash::Error;
 use crate::pac;
 
-pub(crate) const MAX_WRITE_SIZE: usize = super::BANK1_REGION3::WRITE_SIZE;
+fn is_dual_bank() -> bool {
-pub(crate) const MAX_ERASE_SIZE: usize = super::BANK1_REGION3::ERASE_SIZE;
-
-unsafe fn is_dual_bank() -> bool {
     match FLASH_SIZE / 1024 {
         // 1 MB devices depend on configuration
         1024 => {
             if cfg!(any(stm32f427, stm32f429, stm32f437, stm32f439, stm32f469, stm32f479)) {
-                pac::FLASH.optcr().read().db1m()
+                unsafe { pac::FLASH.optcr().read().db1m() }
             } else {
                 false
             }
@@ -38,19 +34,22 @@ pub(crate) unsafe fn unlock() {
     pac::FLASH.keyr().write(|w| w.set_key(0xCDEF_89AB));
 }
 
-pub(crate) unsafe fn blocking_write(first_address: u32, buf: &[u8]) -> Result<(), Error> {
+pub(crate) unsafe fn begin_write() {
+    assert_eq!(0, WRITE_SIZE % 4);
+
     pac::FLASH.cr().write(|w| {
         w.set_pg(true);
         w.set_psize(pac::flash::vals::Psize::PSIZE32);
     });
+}
 
-    let ret = {
+pub(crate) unsafe fn end_write() {
-        let mut ret: Result<(), Error> = Ok(());
+    pac::FLASH.cr().write(|w| w.set_pg(false));
-        let mut address = first_address;
+}
-        for chunk in buf.chunks(MAX_WRITE_SIZE) {
+
-            let vals = chunk.chunks_exact(size_of::<u32>());
+pub(crate) unsafe fn blocking_write(start_address: u32, buf: &[u8; WRITE_SIZE]) -> Result<(), Error> {
-            assert!(vals.remainder().is_empty());
+    let mut address = start_address;
-            for val in vals {
+    for val in buf.chunks(4) {
         write_volatile(address as *mut u32, u32::from_le_bytes(val.try_into().unwrap()));
         address += val.len() as u32;
 
@@ -58,29 +57,30 @@ pub(crate) unsafe fn blocking_write(first_address: u32, buf: &[u8]) -> Result<()
         fence(Ordering::SeqCst);
     }
 
-            ret = blocking_wait_ready();
+    blocking_wait_ready()
-            if ret.is_err() {
-                break;
-            }
-        }
-        ret
-    };
-
-    pac::FLASH.cr().write(|w| w.set_pg(false));
-
-    ret
 }
 
-pub(crate) unsafe fn blocking_erase(from_address: u32, to_address: u32) -> Result<(), Error> {
+pub(crate) fn is_eraseable_range(start_address: u32, end_address: u32) -> bool {
-    let mut addr = from_address;
     let dual_bank = is_dual_bank();
-
+    let mut address = start_address;
-    while addr < to_address {
+    while address < end_address {
-        let sector = get_sector(addr, dual_bank, FLASH_SIZE as u32);
+        let sector = get_sector(address, dual_bank, FLASH_SIZE as u32);
-        erase_sector(sector.index)?;
+        if sector.start != address {
-        addr += sector.size;
+            return false;
         }
+        address += sector.size;
+    }
+    address == end_address
+}
 
+pub(crate) unsafe fn blocking_erase(start_address: u32, end_address: u32) -> Result<(), Error> {
+    let dual_bank = is_dual_bank();
+    let mut address = start_address;
+    while address < end_address {
+        let sector = get_sector(address, dual_bank, FLASH_SIZE as u32);
+        erase_sector(sector.index)?;
+        address += sector.size;
+    }
     Ok(())
 }
 
@@ -116,7 +116,7 @@ pub(crate) unsafe fn clear_all_err() {
     });
 }
 
-pub(crate) unsafe fn blocking_wait_ready() -> Result<(), Error> {
+unsafe fn blocking_wait_ready() -> Result<(), Error> {
     loop {
         let sr = pac::FLASH.sr().read();
 

embassy-stm32/src/flash/f7.rs

@@ -1,17 +1,13 @@
 use core::convert::TryInto;
-use core::mem::size_of;
 use core::ptr::write_volatile;
 use core::sync::atomic::{fence, Ordering};
 
 use embassy_hal_common::stm32::flash::f7::get_sector;
 
-use super::FlashRegion;
+use super::WRITE_SIZE;
 use crate::flash::Error;
 use crate::pac;
 
-pub(crate) const MAX_WRITE_SIZE: usize = super::BANK1_REGION3::WRITE_SIZE;
-pub(crate) const MAX_ERASE_SIZE: usize = super::BANK1_REGION3::ERASE_SIZE;
-
 pub(crate) unsafe fn lock() {
     pac::FLASH.cr().modify(|w| w.set_lock(true));
 }
@@ -21,19 +17,22 @@ pub(crate) unsafe fn unlock() {
     pac::FLASH.keyr().write(|w| w.set_key(0xCDEF_89AB));
 }
 
-pub(crate) unsafe fn blocking_write(first_address: u32, buf: &[u8]) -> Result<(), Error> {
+pub(crate) unsafe fn begin_write() {
+    assert_eq!(0, WRITE_SIZE % 4);
+
     pac::FLASH.cr().write(|w| {
         w.set_pg(true);
         w.set_psize(pac::flash::vals::Psize::PSIZE32);
     });
+}
 
-    let ret = {
+pub(crate) unsafe fn end_write() {
-        let mut ret: Result<(), Error> = Ok(());
+    pac::FLASH.cr().write(|w| w.set_pg(false));
-        let mut address = first_address;
+}
-        for chunk in buf.chunks(MAX_WRITE_SIZE) {
+
-            let vals = chunk.chunks_exact(size_of::<u32>());
+pub(crate) unsafe fn blocking_write(start_address: u32, buf: &[u8; WRITE_SIZE]) -> Result<(), Error> {
-            assert!(vals.remainder().is_empty());
+    let mut address = start_address;
-            for val in vals {
+    for val in buf.chunks(4) {
         write_volatile(address as *mut u32, u32::from_le_bytes(val.try_into().unwrap()));
         address += val.len() as u32;
 
@@ -41,29 +40,28 @@ pub(crate) unsafe fn blocking_write(first_address: u32, buf: &[u8]) -> Result<()
         fence(Ordering::SeqCst);
     }
 
-            ret = blocking_wait_ready();
+    blocking_wait_ready()
-            if ret.is_err() {
-                break;
-            }
-        }
-        ret
-    };
-
-    pac::FLASH.cr().write(|w| w.set_pg(false));
-
-    ret
 }
 
-pub(crate) unsafe fn blocking_erase(from_address: u32, to_address: u32) -> Result<(), Error> {
+pub(crate) fn is_eraseable_range(start_address: u32, end_address: u32) -> bool {
-    let start_sector = get_sector(from_address);
+    let mut address = start_address;
-    let end_sector = get_sector(to_address);
+    while address < end_address {
-    for sector in start_sector.index..end_sector.index {
+        let sector = get_sector(address);
-        let ret = erase_sector(sector as u8);
+        if sector.start != address {
-        if ret.is_err() {
+            return false;
-            return ret;
         }
+        address += sector.size;
     }
+    address == end_address
+}
 
+pub(crate) unsafe fn blocking_erase(start_address: u32, end_address: u32) -> Result<(), Error> {
+    let mut address = start_address;
+    while address < end_address {
+        let sector = get_sector(address);
+        erase_sector(sector.index)?;
+        address += sector.size;
+    }
     Ok(())
 }
 
@@ -106,7 +104,7 @@ pub(crate) unsafe fn clear_all_err() {
     });
 }
 
-pub(crate) unsafe fn blocking_wait_ready() -> Result<(), Error> {
+unsafe fn blocking_wait_ready() -> Result<(), Error> {
     loop {
         let sr = pac::FLASH.sr().read();
 

embassy-stm32/src/flash/h7.rs

@@ -1,15 +1,13 @@
 use core::convert::TryInto;
-use core::mem::size_of;
 use core::ptr::write_volatile;
 
-use super::{FlashRegion, FLASH_SIZE};
+use atomic_polyfill::{fence, Ordering};
+
+use super::{FlashRegion, FLASH_SIZE, WRITE_SIZE};
 use crate::flash::Error;
 use crate::pac;
 
-const WRITE_SIZE: usize = super::BANK1::WRITE_SIZE;
 const ERASE_SIZE: usize = super::BANK1::ERASE_SIZE;
-pub(crate) const MAX_WRITE_SIZE: usize = WRITE_SIZE;
-pub(crate) const MAX_ERASE_SIZE: usize = ERASE_SIZE;
 const SECOND_BANK_OFFSET: usize = 0x0010_0000;
 
 const fn is_dual_bank() -> bool {
@@ -33,59 +31,60 @@ pub(crate) unsafe fn unlock() {
     }
 }
 
-pub(crate) unsafe fn blocking_write(first_address: u32, buf: &[u8]) -> Result<(), Error> {
+pub(crate) unsafe fn begin_write() {
-    let bank = if !is_dual_bank() || (first_address - super::FLASH_BASE as u32) < SECOND_BANK_OFFSET as u32 {
+    assert_eq!(0, WRITE_SIZE % 4);
+}
+
+pub(crate) unsafe fn end_write() {}
+
+pub(crate) unsafe fn blocking_write(start_address: u32, buf: &[u8; WRITE_SIZE]) -> Result<(), Error> {
+    // We cannot have the write setup sequence in begin_write as it depends on the address
+    let bank = if !is_dual_bank() || (start_address - super::FLASH_BASE as u32) < SECOND_BANK_OFFSET as u32 {
         pac::FLASH.bank(0)
     } else {
         pac::FLASH.bank(1)
     };
-
     bank.cr().write(|w| {
         w.set_pg(true);
         w.set_psize(2); // 32 bits at once
     });
-
     cortex_m::asm::isb();
     cortex_m::asm::dsb();
-    core::sync::atomic::fence(core::sync::atomic::Ordering::SeqCst);
+    fence(Ordering::SeqCst);
 
-    let ret = {
+    let mut res = None;
-        let mut ret: Result<(), Error> = Ok(());
+    let mut address = start_address;
-        let mut address = first_address;
+    for val in buf.chunks(4) {
-        'outer: for chunk in buf.chunks(WRITE_SIZE) {
-            let vals = chunk.chunks_exact(size_of::<u32>());
-            assert!(vals.remainder().is_empty());
-            for val in vals {
         write_volatile(address as *mut u32, u32::from_le_bytes(val.try_into().unwrap()));
         address += val.len() as u32;
 
-                ret = blocking_wait_ready(bank);
+        res = Some(blocking_wait_ready(bank));
         bank.sr().modify(|w| {
             if w.eop() {
                 w.set_eop(true);
             }
         });
-                if ret.is_err() {
+        if res.unwrap().is_err() {
-                    break 'outer;
+            break;
         }
     }
-        }
-        ret
-    };
 
     bank.cr().write(|w| w.set_pg(false));
 
     cortex_m::asm::isb();
     cortex_m::asm::dsb();
-    core::sync::atomic::fence(core::sync::atomic::Ordering::SeqCst);
+    fence(Ordering::SeqCst);
 
-    ret
+    res.unwrap()
 }
 
-pub(crate) unsafe fn blocking_erase(from: u32, to: u32) -> Result<(), Error> {
+pub(crate) fn is_eraseable_range(start_address: u32, end_address: u32) -> bool {
-    let start_sector = (from - super::FLASH_BASE as u32) / ERASE_SIZE as u32;
+    start_address % ERASE_SIZE as u32 == 0 && end_address % ERASE_SIZE as u32 == 0
-    let end_sector = (to - super::FLASH_BASE as u32) / ERASE_SIZE as u32;
+}
 
+pub(crate) unsafe fn blocking_erase(start_address: u32, end_address: u32) -> Result<(), Error> {
+    let start_sector = (start_address - super::FLASH_BASE as u32) / ERASE_SIZE as u32;
+    let end_sector = (end_address - super::FLASH_BASE as u32) / ERASE_SIZE as u32;
     for sector in start_sector..end_sector {
         let bank = if sector >= 8 { 1 } else { 0 };
         let ret = erase_sector(pac::FLASH.bank(bank), (sector % 8) as u8);
@@ -93,7 +92,6 @@ pub(crate) unsafe fn blocking_erase(from: u32, to: u32) -> Result<(), Error> {
             return ret;
         }
     }
-
     Ok(())
 }
 
@@ -157,7 +155,7 @@ unsafe fn bank_clear_all_err(bank: pac::flash::Bank) {
     });
 }
 
-pub(crate) unsafe fn blocking_wait_ready(bank: pac::flash::Bank) -> Result<(), Error> {
+unsafe fn blocking_wait_ready(bank: pac::flash::Bank) -> Result<(), Error> {
     loop {
         let sr = bank.sr().read();
 

embassy-stm32/src/flash/l.rs

@@ -1,14 +1,12 @@
-use core::convert::TryInto;
 use core::ptr::write_volatile;
 
-use super::FlashRegion;
+use atomic_polyfill::{fence, Ordering};
+
+use super::{FlashRegion, WRITE_SIZE};
 use crate::flash::Error;
 use crate::pac;
 
-const WRITE_SIZE: usize = super::BANK1::WRITE_SIZE;
 const ERASE_SIZE: usize = super::BANK1::ERASE_SIZE;
-pub(crate) const MAX_WRITE_SIZE: usize = WRITE_SIZE;
-pub(crate) const MAX_ERASE_SIZE: usize = ERASE_SIZE;
 
 pub(crate) unsafe fn lock() {
     #[cfg(any(flash_wl, flash_wb, flash_l4))]
@@ -39,35 +37,37 @@ pub(crate) unsafe fn unlock() {
     }
 }
 
-pub(crate) unsafe fn blocking_write(first_address: u32, buf: &[u8]) -> Result<(), Error> {
+pub(crate) unsafe fn begin_write() {
+    assert_eq!(0, WRITE_SIZE % 4);
+
     #[cfg(any(flash_wl, flash_wb, flash_l4))]
     pac::FLASH.cr().write(|w| w.set_pg(true));
-
-    let ret = {
-        let mut ret: Result<(), Error> = Ok(());
-        let mut address = first_address;
-        for chunk in buf.chunks(WRITE_SIZE) {
-            for val in chunk.chunks(4) {
-                write_volatile(address as *mut u32, u32::from_le_bytes(val[0..4].try_into().unwrap()));
-                address += val.len() as u32;
-            }
-
-            ret = blocking_wait_ready();
-            if ret.is_err() {
-                break;
-            }
-        }
-        ret
-    };
-
-    #[cfg(any(flash_wl, flash_wb, flash_l4))]
-    pac::FLASH.cr().write(|w| w.set_pg(false));
-
-    ret
 }
 
-pub(crate) unsafe fn blocking_erase(from_address: u32, to_address: u32) -> Result<(), Error> {
+pub(crate) unsafe fn end_write() {
-    for page in (from_address..to_address).step_by(ERASE_SIZE) {
+    #[cfg(any(flash_wl, flash_wb, flash_l4))]
+    pac::FLASH.cr().write(|w| w.set_pg(false));
+}
+
+pub(crate) unsafe fn blocking_write(start_address: u32, buf: &[u8; WRITE_SIZE]) -> Result<(), Error> {
+    let mut address = start_address;
+    for val in buf.chunks(4) {
+        write_volatile(address as *mut u32, u32::from_le_bytes(val.try_into().unwrap()));
+        address += val.len() as u32;
+
+        // prevents parallelism errors
+        fence(Ordering::SeqCst);
+    }
+
+    blocking_wait_ready()
+}
+
+pub(crate) fn is_eraseable_range(start_address: u32, end_address: u32) -> bool {
+    start_address % ERASE_SIZE as u32 == 0 && end_address % ERASE_SIZE as u32 == 0
+}
+
+pub(crate) unsafe fn blocking_erase(start_address: u32, end_address: u32) -> Result<(), Error> {
+    for page in (start_address..end_address).step_by(ERASE_SIZE) {
         #[cfg(any(flash_l0, flash_l1))]
         {
             pac::FLASH.pecr().modify(|w| {
@@ -155,7 +155,7 @@ pub(crate) unsafe fn clear_all_err() {
     });
 }
 
-pub(crate) unsafe fn blocking_wait_ready() -> Result<(), Error> {
+unsafe fn blocking_wait_ready() -> Result<(), Error> {
     loop {
         let sr = pac::FLASH.sr().read();
 

embassy-stm32/src/flash/mod.rs

@@ -1,8 +1,10 @@
 use embassy_hal_common::{into_ref, PeripheralRef};
+use embassy_sync::blocking_mutex::raw::CriticalSectionRawMutex;
+use embassy_sync::mutex::{Mutex, MutexGuard};
 use embedded_storage::nor_flash::{ErrorType, NorFlash, NorFlashError, NorFlashErrorKind, ReadNorFlash};
 
 pub use crate::_generated::flash_regions::*;
-pub use crate::pac::{FLASH_BASE, FLASH_SIZE};
+pub use crate::pac::{FLASH_BASE, FLASH_SIZE, WRITE_SIZE};
 use crate::peripherals::FLASH;
 use crate::Peripheral;
 
@@ -17,6 +19,8 @@ pub struct Flash<'d> {
     _inner: PeripheralRef<'d, FLASH>,
 }
 
+static REGION_LOCK: Mutex<CriticalSectionRawMutex, ()> = Mutex::new(());
+
 impl<'d> Flash<'d> {
     pub fn new(p: impl Peripheral<P = FLASH> + 'd) -> Self {
         into_ref!(p);
@@ -33,7 +37,6 @@ impl<'d> Flash<'d> {
         }
 
         let first_address = FLASH_BASE as u32 + offset;
-
         let flash_data = unsafe { core::slice::from_raw_parts(first_address as *const u8, bytes.len()) };
         bytes.copy_from_slice(flash_data);
         Ok(())
@@ -43,39 +46,56 @@ impl<'d> Flash<'d> {
         if offset as usize + buf.len() > FLASH_SIZE {
             return Err(Error::Size);
         }
-        if offset as usize % family::MAX_WRITE_SIZE != 0 || buf.len() as usize % family::MAX_WRITE_SIZE != 0 {
+        if offset as usize % WRITE_SIZE != 0 || buf.len() as usize % WRITE_SIZE != 0 {
             return Err(Error::Unaligned);
         }
 
-        let first_address = FLASH_BASE as u32 + offset;
+        let start_address = FLASH_BASE as u32 + offset;
-        trace!("Writing {} bytes at 0x{:x}", buf.len(), first_address);
+        trace!("Writing {} bytes at 0x{:x}", buf.len(), start_address);
+
+        // No need to take lock here as we only have one mut flash reference.
 
         unsafe {
             family::clear_all_err();
-
             family::unlock();
-            let res = family::blocking_write(first_address, buf);
+            let res = Flash::blocking_write_all(start_address, buf);
             family::lock();
             res
         }
     }
 
+    unsafe fn blocking_write_all(start_address: u32, buf: &[u8]) -> Result<(), Error> {
+        family::begin_write();
+        let mut address = start_address;
+        for chunk in buf.chunks(WRITE_SIZE) {
+            let res = unsafe { family::blocking_write(address, chunk.try_into().unwrap()) };
+            if res.is_err() {
+                family::end_write();
+                return res;
+            }
+            address += WRITE_SIZE as u32;
+        }
+
+        family::end_write();
+        Ok(())
+    }
+
     pub fn blocking_erase(&mut self, from: u32, to: u32) -> Result<(), Error> {
         if to < from || to as usize > FLASH_SIZE {
             return Err(Error::Size);
         }
-        if (from as usize % family::MAX_ERASE_SIZE) != 0 || (to as usize % family::MAX_ERASE_SIZE) != 0 {
+
+        let start_address = FLASH_BASE as u32 + from;
+        let end_address = FLASH_BASE as u32 + to;
+        if !family::is_eraseable_range(start_address, end_address) {
             return Err(Error::Unaligned);
         }
-
+        trace!("Erasing from 0x{:x} to 0x{:x}", start_address, end_address);
-        let from_address = FLASH_BASE as u32 + from;
-        let to_address = FLASH_BASE as u32 + to;
 
         unsafe {
             family::clear_all_err();
-
             family::unlock();
-            let res = family::blocking_erase(from_address, to_address);
+            let res = family::blocking_erase(start_address, end_address);
             family::lock();
             res
         }
@@ -101,7 +121,6 @@ pub trait FlashRegion {
         }
 
         let first_address = Self::BASE as u32 + offset;
-
         let flash_data = unsafe { core::slice::from_raw_parts(first_address as *const u8, bytes.len()) };
         bytes.copy_from_slice(flash_data);
         Ok(())
@@ -115,17 +134,19 @@ pub trait FlashRegion {
             return Err(Error::Unaligned);
         }
 
-        let first_address = Self::BASE as u32 + offset;
+        let start_address = Self::BASE as u32 + offset;
-        trace!("Writing {} bytes from 0x{:x}", buf.len(), first_address);
+        trace!("Writing {} bytes from 0x{:x}", buf.len(), start_address);
 
-        critical_section::with(|_| unsafe {
+        // Protect agains simultaneous write/erase to multiple regions.
+        let _guard = take_lock_spin();
+
+        unsafe {
             family::clear_all_err();
-
             family::unlock();
-            let res = family::blocking_write(first_address, buf);
+            let res = Flash::blocking_write_all(start_address, buf);
             family::lock();
             res
-        })
+        }
     }
 
     fn blocking_erase(&mut self, from: u32, to: u32) -> Result<(), Error> {
@@ -136,18 +157,28 @@ pub trait FlashRegion {
             return Err(Error::Unaligned);
         }
 
-        let from_address = Self::BASE as u32 + from;
+        let start_address = Self::BASE as u32 + from;
-        let to_address = Self::BASE as u32 + to;
+        let end_address = Self::BASE as u32 + to;
-        trace!("Erasing from 0x{:x} to 0x{:x}", from_address, to_address);
+        trace!("Erasing from 0x{:x} to 0x{:x}", start_address, end_address);
 
-        critical_section::with(|_| unsafe {
+        // Protect agains simultaneous write/erase to multiple regions.
+        let _guard = take_lock_spin();
+
+        unsafe {
             family::clear_all_err();
-
             family::unlock();
-            let res = family::blocking_erase(from_address, to_address);
+            let res = family::blocking_erase(start_address, end_address);
             family::lock();
             res
-        })
+        }
+    }
+}
+
+fn take_lock_spin() -> MutexGuard<'static, CriticalSectionRawMutex, ()> {
+    loop {
+        if let Ok(guard) = REGION_LOCK.try_lock() {
+            return guard;
+        }
     }
 }