Am Donnerstag, 17. August 2017, 20:25:17 CEST schrieb PrasannaKumar 
Muralidharan:

Hi PrasannaKumar,

+
+static int jz4780_rng_generate(struct crypto_rng *tfm,
+			       const u8 *src, unsigned int slen,
+			       u8 *dst, unsigned int dlen)
+{
+	struct jz4780_rng_ctx *ctx = crypto_rng_ctx(tfm);
+	struct jz4780_rng *rng = ctx->rng;
+	u32 data;
+
+	/*
+	 * JZ4780 Programmers manual says the RNG should not run continuously
+	 * for more than 1s. So enable RNG, read data and disable it.
+	 * NOTE: No issue was observed with MIPS creator CI20 board even when
+	 * RNG ran continuously for longer periods. This is just a precaution.
+	 *
+	 * A delay is required so that the current RNG data is not bit shifted
+	 * version of previous RNG data which could happen if random data is
+	 * read continuously from this device.
+	 */
+	jz4780_rng_writel(rng, 1, REG_RNG_CTRL);
+	do {
+		data = jz4780_rng_readl(rng, REG_RNG_DATA);
+		memcpy((void *)dst, (void *)&data, 4);

How do you know that dst is a multiple of 4 bytes? When dlen is only 3, you 
overflow the buffer.

+		dlen -= 4;
+		dst += 4;
+		udelay(20);
+	} while (dlen >= 4);
+
+	if (dlen > 0) {
+		data = jz4780_rng_readl(rng, REG_RNG_DATA);
+		memcpy((void *)dst, (void *)&data, dlen);
+	}
+	jz4780_rng_writel(rng, 0, REG_RNG_CTRL);
+
+	return 0;
+}

Ciao
Stephan