hw_random: timeriomem_rng: Allow setting RNG quality from platform data

When a hw_random device's quality is non-zero, it will automatically be
used to fill the kernel's entropy pool.  Since timeriomem_rng is used by
many different devices, the quality needs to be provided by platform
data or device tree.
Signed-off-by: Rick Altherr <raltherr@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/char/hw_random/timeriomem-rng.c

@@ -151,8 +151,15 @@ static int timeriomem_rng_probe(struct platform_device *pdev)
 			dev_err(&pdev->dev, "missing period\n");
 			return -EINVAL;
 		}
+
+		if (!of_property_read_u32(pdev->dev.of_node,
+						"quality", &i))
+			priv->rng_ops.quality = i;
+		else
+			priv->rng_ops.quality = 0;
 	} else {
 		period = pdata->period;
+		priv->rng_ops.quality = pdata->quality;
 	}
 
 	priv->period = ns_to_ktime(period * NSEC_PER_USEC);

include/linux/timeriomem-rng.h

@@ -13,4 +13,7 @@ struct timeriomem_rng_data {
 
 	/* measures in usecs */
 	unsigned int		period;
+
+	/* bits of entropy per 1024 bits read */
+	unsigned int		quality;
 };