hwrng: omap - Fix RNG wait loop timeout
authorSumit Garg <sumit.garg@linaro.org>
Mon, 14 Oct 2019 12:02:45 +0000 (17:32 +0530)
committerHerbert Xu <herbert@gondor.apana.org.au>
Fri, 25 Oct 2019 15:06:04 +0000 (02:06 +1100)
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: 383212425c92 ("hwrng: omap - Add device variant for SafeXcel IP-76 found in Armada 8K")
Cc: <stable@vger.kernel.org>
Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
drivers/char/hw_random/omap-rng.c

index b27f39688b5e71de16650bb7a67c29a54b7539dd..e329f82c0467fffdcbe8c54732089d9735adc95b 100644 (file)
 #define OMAP4_RNG_OUTPUT_SIZE                  0x8
 #define EIP76_RNG_OUTPUT_SIZE                  0x10
 
 #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,
 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;
 
        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;
                present = priv->pdata->data_present(priv);
                if (present || !wait)
                        break;