Merge pull request #165 from bobmcwhirter/rng_impl

Rng impl

embassy-stm32/Cargo.toml

@@ -15,6 +15,7 @@ cortex-m-rt = { version = "0.6.13", features = ["device"] }
 cortex-m = "0.7.1"
 embedded-hal    = { version = "0.2.4" }
 futures = { version = "0.3.5", default-features = false, features = ["async-await"] }
+rand_core = { version = "0.6.2", optional=true}
 
 [build-dependencies]
 regex = "1.4.6"
@@ -321,7 +322,7 @@ _exti = []
 _exti_v1 = []
 _gpio = []
 _gpio_v2 = []
-_rng = []
+_rng = [ "rand_core",]
 _rng_v1 = []
 _stm32f4 = []
 _stm32l4 = []

embassy-stm32/gen.py

@@ -201,6 +201,9 @@ for chip in chips.values():
 
 # ========= Update Cargo features
 
+feature_optional_deps = {}
+feature_optional_deps['_rng'] = ['rand_core']
+
 features = {}
 extra_features = set()
 for name, chip in chips.items():
@@ -208,7 +211,7 @@ for name, chip in chips.items():
     for feature in chip['features']:
         extra_features.add(feature)
 for feature in sorted(list(extra_features)):
-    features[feature] = []
+    features[feature] = feature_optional_deps.get(feature) or []
 
 SEPARATOR_START = '# BEGIN GENERATED FEATURES\n'
 SEPARATOR_END = '# END GENERATED FEATURES\n'

embassy-stm32/src/lib.rs

@@ -15,6 +15,7 @@ pub mod exti;
 pub mod gpio;
 #[cfg(feature = "_rng")]
 pub mod rng;
+#[cfg(feature = "_usart")]
 pub mod usart;
 
 // This must go LAST so that it sees the `impl_foo!` macros

embassy-stm32/src/rng.rs

@@ -1,8 +1,26 @@
 #![macro_use]
-use crate::pac::rng::{regs, Rng};
+
+//use crate::pac::rng::{regs, Rng};
+use crate::pac;
 use crate::peripherals;
-use embassy::util::Unborrow;
+use crate::interrupt;
+use futures::future::poll_fn;
+use embassy::util::{Unborrow, AtomicWaker};
 use embassy_extras::unborrow;
+use rand_core::{RngCore, CryptoRng};
+
+use defmt::*;
+
+static RNG_WAKER: AtomicWaker = AtomicWaker::new();
+
+#[interrupt]
+unsafe fn RNG() {
+    let bits = crate::pac::RNG.sr().read();
+    if bits.drdy() || bits.seis() || bits.ceis() {
+        crate::pac::RNG.cr().write(|reg| reg.set_ie(false));
+        RNG_WAKER.wake();
+    }
+}
 
 pub struct Random<T: Instance> {
     inner: T,
@@ -11,21 +29,112 @@ pub struct Random<T: Instance> {
 impl<T: Instance> Random<T> {
     pub fn new(inner: impl Unborrow<Target=T>) -> Self {
         unborrow!(inner);
-        Self { inner }
+        let mut random = Self { inner };
+        random.reset();
+        random
+    }
+
+    pub fn reset(&mut self) {
+        unsafe {
+            T::regs().cr().modify(|reg| {
+                reg.set_rngen(true);
+                reg.set_ie(true);
+            });
+            T::regs().sr().modify(|reg| {
+                reg.set_seis(false);
+                reg.set_ceis(false);
+            });
+        }
+        // Reference manual says to discard the first.
+        let _ = self.next_u32();
     }
 }
 
+impl<T: Instance> RngCore for Random<T> {
+    fn next_u32(&mut self) -> u32 {
+        loop {
+            let bits = unsafe { T::regs().sr().read() };
+            if bits.drdy() {
+                return unsafe{ T::regs().dr().read() }
+            }
+        }
+    }
+
+    fn next_u64(&mut self) -> u64 {
+        let mut rand = self.next_u32() as u64;
+        rand |= (self.next_u32() as u64) << 32;
+        rand
+    }
+
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        for chunk in dest.chunks_mut(4) {
+            let rand = self.next_u32();
+            for (slot, num) in chunk.iter_mut().zip(rand.to_be_bytes().iter()) {
+                *slot = *num
+            }
+        }
+    }
+
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), rand_core::Error> {
+        self.fill_bytes( dest );
+        Ok(())
+    }
+}
+
+impl<T: Instance> CryptoRng for Random<T> { }
+
 use core::future::Future;
 use core::marker::PhantomData;
-use embassy::traits::rng::Rng as RngTrait;
+use embassy::traits;
+use core::task::{Poll, Context};
+use core::pin::Pin;
 
-impl<T: Instance> RngTrait for Random<T> {
-    type Error = ();
-    #[rustfmt::skip]
+pub enum Error {
+    SeedError,
+    ClockError,
+}
+
+impl<T: Instance> traits::rng::Rng for Random<T> {
+    type Error = Error;
     type RngFuture<'a> where Self: 'a = impl Future<Output=Result<(), Self::Error>>;
 
-    fn fill<'a>(&'a mut self, dest: &'a mut [u8]) -> Self::RngFuture<'a> {
-        async move { Ok(()) }
+    fn fill_bytes<'a>(&'a mut self, dest: &'a mut [u8]) -> Self::RngFuture<'a> {
+        unsafe {
+            T::regs().cr().modify(|reg| {
+                reg.set_rngen(true);
+            });
+        }
+        async move {
+            for chunk in dest.chunks_mut(4) {
+                poll_fn(|cx| {
+                    RNG_WAKER.register(cx.waker());
+                    unsafe {
+                        T::regs().cr().modify(|reg| {
+                            reg.set_ie(true);
+                        });
+                    }
+
+                    let bits = unsafe { T::regs().sr().read() };
+
+                    if bits.drdy() {
+                        Poll::Ready(Ok(()))
+                    } else if bits.seis() {
+                        self.reset();
+                        Poll::Ready(Err(Error::SeedError))
+                    } else if bits.ceis() {
+                        self.reset();
+                        Poll::Ready(Err(Error::ClockError))
+                    } else {
+                        Poll::Pending
+                    }
+                } ).await?;
+                let random_bytes = unsafe { T::regs().dr().read() }.to_be_bytes();
+                for (dest, src) in chunk.iter_mut().zip(random_bytes.iter()) {
+                    *dest = *src
+                }
+            }
+            Ok(())
+        }
     }
 }
 
@@ -33,7 +142,7 @@ pub(crate) mod sealed {
     use super::*;
 
     pub trait Instance {
-        fn regs(&self) -> Rng;
+        fn regs() -> pac::rng::Rng;
     }
 }
 
@@ -41,12 +150,12 @@ pub trait Instance: sealed::Instance {}
 
 macro_rules! impl_rng {
     ($inst:ident) => {
-        impl crate::rng::sealed::Instance for peripherals::$inst {
-            fn regs(&self) -> crate::pac::rng::Rng {
-                crate::pac::$inst
+        impl crate::rng::sealed::Instance for peripherals::RNG {
+            fn regs() -> crate::pac::chip::rng::Rng {
+                crate::pac::RNG
             }
         }
 
-        impl crate::rng::Instance for peripherals::$inst {}
+        impl crate::rng::Instance for peripherals::RNG {}
     };
 }

embassy-traits/src/rng.rs

@@ -13,5 +13,5 @@ pub trait Rng {
     /// May result in delays if entropy is exhausted prior to completely
     /// filling the buffer. Upon completion, the buffer will be completely
     /// filled or an error will have been reported.
-    fn fill<'a>(&'a mut self, dest: &'a mut [u8]) -> Self::RngFuture<'a>;
+    fn fill_bytes<'a>(&'a mut self, dest: &'a mut [u8]) -> Self::RngFuture<'a>;
 }