From 5866852a901d420523f94c505c904826c0286f64 Mon Sep 17 00:00:00 2001
From: Guillaume Revaillot <revaillot@archos.com>
Date: Tue, 5 Feb 2019 17:17:34 +0100
Subject: [PATCH] rng: handle noise source / seed error.

If noise source error occurs, flag must be cleared and data register
must be discarded (at least 12 reads to flush pipeline on G0). Other
device mention start/restart of chip, so, do both (better safe than
sorry).

Reviewed-on: https://github.com/libopencm3/libopencm3/pull/1062
---
 lib/stm32/common/rng_common_v1.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/lib/stm32/common/rng_common_v1.c b/lib/stm32/common/rng_common_v1.c
index bffb0c27..e35fc46a 100644
--- a/lib/stm32/common/rng_common_v1.c
+++ b/lib/stm32/common/rng_common_v1.c
@@ -94,10 +94,16 @@ uint32_t rng_get_random_blocking(void)
         uint32_t rv;
         bool done;
         do {
-                if (RNG_SR & RNG_SR_SECS) {
-                        rng_disable();
-                        rng_enable();
+
+                if (RNG_SR & RNG_SR_SEIS) {
+                        RNG_SR = RNG_SR & ~RNG_SR_SEIS;
+                        for (int i = 12; i != 0; i--) {
+                                rv = RNG_DR;
+                        }
+                        RNG_CR &= ~RNG_CR_RNGEN;
+                        RNG_CR |= RNG_CR_RNGEN;
                 }
+
                 done = rng_get_random(&rv);
         } while (!done);