hwrng: omap - Fix RNG wait loop timeout

Existing RNG data read timeout is 200us but it doesn't cover EIP76 RNG data rate which takes approx. 700us to produce 16 bytes of output data as per testing results. So configure the timeout as 1000us to also take account of lack of udelay()'s reliability. Fixes: 3832124 ("hwrng: omap - Add device variant for SafeXcel IP-76 found in Armada 8K") Cc: <[email protected]> Signed-off-by: Sumit Garg <[email protected]> Signed-off-by: Herbert Xu <[email protected]>
mrcsosa · Oct 25, 2019 · be867f9 · be867f9
1 parent e9fc367
commit be867f9
Showing 1 changed file with 8 additions and 1 deletion.
diff --git a/drivers/char/hw_random/omap-rng.c b/drivers/char/hw_random/omap-rng.c
@@ -66,6 +66,13 @@
 #define OMAP4_RNG_OUTPUT_SIZE			0x8
 #define EIP76_RNG_OUTPUT_SIZE			0x10
 
+/*
+ * EIP76 RNG takes approx. 700us to produce 16 bytes of output data
+ * as per testing results. And to account for the lack of udelay()'s
+ * reliability, we keep the timeout as 1000us.
+ */
+#define RNG_DATA_FILL_TIMEOUT			100
+
 enum {
 	RNG_OUTPUT_0_REG = 0,
 	RNG_OUTPUT_1_REG,
@@ -176,7 +183,7 @@ static int omap_rng_do_read(struct hwrng *rng, void *data, size_t max,
 	if (max < priv->pdata->data_size)
 		return 0;
 
-	for (i = 0; i < 20; i++) {
+	for (i = 0; i < RNG_DATA_FILL_TIMEOUT; i++) {
 		present = priv->pdata->data_present(priv);
 		if (present || !wait)
 			break;