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authorlionel.debieve@st.com <lionel.debieve@st.com>2018-02-15 14:03:12 +0100
committerHerbert Xu <herbert@gondor.apana.org.au>2018-03-03 00:03:11 +0800
commit279f4f8f2f67b7a2dbb916738667a633b223efde (patch)
treeeda4148ed31d72bc4fbc590294916230fed8e4ce /drivers/char/hw_random
parenta888df9b89b785c6dc6fcbf886f0ccda57f98b3a (diff)
hwrng: stm32 - rework read timeout calculation
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.debieve@st.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'drivers/char/hw_random')
-rw-r--r--drivers/char/hw_random/stm32-rng.c25
1 files 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... */