From 53092a7780fa3d1b926aae8666f1c5a19cb039f1 Mon Sep 17 00:00:00 2001
From: Gatien Chevallier <gatien.chevallier@foss.st.com>
Date: Fri, 26 May 2023 15:49:03 +0200
Subject: [PATCH] fix(st-crypto): do not read RNG data if it's not ready

Having RNG_SR_DRDY bit in RNG_SR register does not mean that there are 4
RNG words ready to be read. Add a check on RNG_SR_DRDY between each word
reading.

Signed-off-by: Gatien Chevallier <gatien.chevallier@foss.st.com>
Change-Id: I46af7ca6c0ddbe19540b248365a5016b15b9a707
---
 drivers/st/crypto/stm32_rng.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/st/crypto/stm32_rng.c b/drivers/st/crypto/stm32_rng.c
index a9dc43f8d..1342fd454 100644
--- a/drivers/st/crypto/stm32_rng.c
+++ b/drivers/st/crypto/stm32_rng.c
@@ -187,6 +187,10 @@ int stm32_rng_read(uint8_t *out, uint32_t size)
 
 		count = 4U;
 		while (len != 0U) {
+			if ((mmio_read_32(stm32_rng.base + RNG_SR) & RNG_SR_DRDY) == 0U) {
+				break;
+			}
+
 			data32 = mmio_read_32(stm32_rng.base + RNG_DR);
 			count--;