Increase timeout delay to support longer timing linked
to rng initialization. Measurement is based on timer instead
of instructions per iteration which is not powerful on all
targets.
Signed-off-by: Lionel Debieve <lionel.debi...@st.com>
---
drivers/char/hw_random/stm32-rng.c | 25 ++++++++++---------------
1 file changed, 10 insertions(+), 15 deletions(-)
diff --git a/drivers/char/hw_random/stm32-rng.c
b/drivers/char/hw_random/stm32-rng.c
index 709a8d061be3..0d2328da3b76 100644
--- a/drivers/char/hw_random/stm32-rng.c
+++ b/drivers/char/hw_random/stm32-rng.c
@@ -16,6 +16,7 @@
#include <linux/delay.h>
#include <linux/hw_random.h>
#include <linux/io.h>
+#include <linux/iopoll.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of_address.h>
@@ -35,15 +36,6 @@
#define RNG_DR 0x08
-/*
- * It takes 40 cycles @ 48MHz to generate each random number (e.g. <1us).
- * At the time of writing STM32 parts max out at ~200MHz meaning a timeout
- * of 500 leaves us a very comfortable margin for error. The loop to which
- * the timeout applies takes at least 4 instructions per iteration so the
- * timeout is enough to take us up to multi-GHz parts!
- */
-#define RNG_TIMEOUT 500
-
struct stm32_rng_private {
struct hwrng rng;
void __iomem *base;
@@ -63,13 +55,16 @@ static int stm32_rng_read(struct hwrng *rng, void *data,
size_t max, bool wait)
while (max > sizeof(u32)) {
sr = readl_relaxed(priv->base + RNG_SR);
+ /* Manage timeout which is based on timer and take */
+ /* care of initial delay time when enabling rng */
if (!sr && wait) {
- unsigned int timeout = RNG_TIMEOUT;
-
- do {
- cpu_relax();
- sr = readl_relaxed(priv->base + RNG_SR);
- } while (!sr && --timeout);
+ retval = readl_relaxed_poll_timeout_atomic(priv->base
+ + RNG_SR,
+ sr, sr,
+ 10, 50000);
+ if (retval)
+ dev_err((struct device *)priv->rng.priv,
+ "%s: timeout %x!\n", __func__, sr);
}
/* If error detected or data not ready... */
--
2.15.1
