From b65406791a718e4e15a388b20c843fff2ab88037 Mon Sep 17 00:00:00 2001
From: Jan Christoph Bernack <jc.bernack@gmail.com>
Date: Sat, 1 Jul 2023 03:15:39 +0200
Subject: [PATCH] add RNG conditioning

---
 embassy-stm32/src/rng.rs | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/embassy-stm32/src/rng.rs b/embassy-stm32/src/rng.rs
index 27415c2d..5d61d036 100644
--- a/embassy-stm32/src/rng.rs
+++ b/embassy-stm32/src/rng.rs
@@ -31,6 +31,7 @@ impl<'d, T: Instance> Rng<'d, T> {
         random
     }
 
+    #[cfg(rng_v1)]
     pub fn reset(&mut self) {
         // rng_v2 locks up on seed error, needs reset
         #[cfg(rng_v2)]
@@ -49,6 +50,38 @@ impl<'d, T: Instance> Rng<'d, T> {
         let _ = self.next_u32();
     }
 
+    #[cfg(not(rng_v1))]
+    pub fn reset(&mut self) {
+        T::regs().cr().modify(|reg| {
+            reg.set_rngen(false);
+            reg.set_condrst(true);
+            // set RNG config "A" according to reference manual
+            // this has to be written within the same write access as setting the CONDRST bit
+            reg.set_nistc(pac::rng::vals::Nistc::DEFAULT);
+            reg.set_rng_config1(pac::rng::vals::RngConfig1::CONFIGA);
+            reg.set_rng_config2(pac::rng::vals::RngConfig2::CONFIGA_B);
+            reg.set_rng_config3(pac::rng::vals::RngConfig3::CONFIGA);
+            reg.set_clkdiv(pac::rng::vals::Clkdiv::NODIV);
+        });
+        // wait for CONDRST to be set
+        while !T::regs().cr().read().condrst() {}
+        // magic number must be written immediately before every read or write access to HTCR
+        T::regs().htcr().write(|w| w.set_htcfg(pac::rng::vals::Htcfg::MAGIC));
+        // write recommended value according to reference manual
+        // note: HTCR can only be written during conditioning
+        T::regs()
+            .htcr()
+            .write(|w| w.set_htcfg(pac::rng::vals::Htcfg::RECOMMENDED));
+        // finish conditioning
+        T::regs().cr().modify(|reg| {
+            reg.set_rngen(true);
+            reg.set_condrst(false);
+            reg.set_ie(true);
+        });
+        // wait for CONDRST to be reset
+        while T::regs().cr().read().condrst() {}
+    }
+
     pub async fn async_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
         T::regs().cr().modify(|reg| {
             reg.set_rngen(true);