feat(rng): add fake async driver

README.md

@@ -77,6 +77,7 @@ This crate is a working-in-progress and not ready for production use.
   - [x] Device
   - [ ] Host
 - [x] XPI NOR flash driver using embedded-storage
+- [x] RNG, in blocking mode
 - [ ] power domain handling
 
 ### Related Crates

examples/hpm5300evk/src/bin/rng.rs

@@ -4,6 +4,7 @@
 #![feature(impl_trait_in_assoc_type)]
 #![feature(abi_riscv_interrupt)]
 
+use embassy_time::Timer;
 use rand_core::RngCore;
 use {defmt_rtt as _, hpm_hal as hal};
 
@@ -14,10 +15,22 @@ async fn main(_spawner: embassy_executor::Spawner) -> ! {
     let mut rng = hal::rng::Rng::new(p.RNG).unwrap();
     let mut buf = [0u8; 20];
 
+    defmt::println!("Async mode");
+
+    for _ in 0..5 {
+        rng.async_fill_bytes(&mut buf).await.unwrap();
+
+        defmt::println!("out: {:?}", buf);
+    }
+
+    Timer::after_millis(1000).await;
+
+    defmt::println!("Blocking mode(Notice about 0.3s delay when new seed is not ready");
+
     loop {
         rng.fill_bytes(&mut buf);
 
-        defmt::println!("buf: {:?}", buf);
+        defmt::println!("out: {:?}", buf);
     }
 }
 

src/rng.rs

@@ -6,6 +6,7 @@
 //! - FIFO underflow
 //!
 
+use embassy_futures::yield_now;
 use embassy_hal_internal::{into_ref, Peripheral, PeripheralRef};
 use rand_core::{CryptoRng, RngCore};
 
@@ -67,6 +68,26 @@ impl<'d, T: Instance> Rng<'d, T> {
         Ok(())
     }
 
+    #[inline]
+    async fn async_next_u32(&mut self) -> Result<u32, Error> {
+        while T::regs().sta().read().busy() {
+            yield_now().await;
+        }
+        Ok(T::regs().fo2b().read().0)
+    }
+
+    // NOTE: RNG interrupt is non-functional.
+    // See-also: https://github.com/hpmicro/hpm-hal/issues/37
+    pub async fn async_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        for chunk in dest.chunks_mut(4) {
+            let rand = self.async_next_u32().await?;
+            for (slot, num) in chunk.iter_mut().zip(rand.to_ne_bytes().iter()) {
+                *slot = *num
+            }
+        }
+        Ok(())
+    }
+
     /// Run self-test
     pub fn run_selftest(&mut self) -> Result<(), Error> {
         let r = T::regs();