Hello
I have just some minor comments below
> diff --git a/drivers/char/hw_random/jz4780-rng.c b/drivers/char/hw_random/jz4780-rng.c
> new file mode 100644
> index 0000000..c9d2cde
> --- /dev/null
> +++ b/drivers/char/hw_random/jz4780-rng.c
> @@ -0,0 +1,105 @@
> +/*
> + * jz4780-rng.c - Random Number Generator driver for J4780
> + *
> + * Copyright 2016 (C) PrasannaKumar Muralidharan <prasannatsmkumar@xxxxxxxxx>
> + *
> + * This file is licensed under the terms of the GNU General Public
> + * License version 2. This program is licensed "as is" without any
> + * warranty of any kind, whether express or implied.
> + */
> +
> +#include <linux/hw_random.h>
> +#include <linux/device.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/io.h>
> +#include <linux/platform_device.h>
> +#include <linux/err.h>
You could sort them by alphabetical order
> +
> +#define REG_RNG_CTRL 0x0
> +#define REG_RNG_DATA 0x4
> +
> +struct jz4780_rng {
> + struct device *dev;
> + struct hwrng rng;
> + void __iomem *mem;
> +};
> +
> +static u32 jz4780_rng_readl(struct jz4780_rng *rng, u32 offset)
> +{
> + return readl(rng->mem + offset);
> +}
> +
> +static void jz4780_rng_writel(struct jz4780_rng *rng, u32 val, u32 offset)
> +{
> + writel(val, rng->mem + offset);
> +}
> +
> +static int jz4780_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
> +{
> + struct jz4780_rng *jz4780_rng = container_of(rng, struct jz4780_rng,
> + rng);
> + u32 *data = buf;
> + *data = jz4780_rng_readl(jz4780_rng, REG_RNG_DATA);
> + return 4;
> +}
If max is less than 4, its bad
> +
> +static int jz4780_rng_probe(struct platform_device *pdev)
> +{
> + struct jz4780_rng *jz4780_rng;
> + struct resource *res;
> + resource_size_t size;
> + int ret;
> +
> + jz4780_rng = devm_kzalloc(&pdev->dev, sizeof(struct jz4780_rng),
> + GFP_KERNEL);
You could write sizeof(*js480_rng)
> + if (!jz4780_rng)
> + return -ENOMEM;
> +
> + jz4780_rng->dev = &pdev->dev;
> + jz4780_rng->rng.name = "jz4780";
> + jz4780_rng->rng.read = jz4780_rng_read;
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + size = resource_size(res);
> +
> + jz4780_rng->mem = devm_ioremap(&pdev->dev, res->start, size);
You could save code by using devm_ioremap_resource (don't need size)
> + if (IS_ERR(jz4780_rng->mem))
> + return PTR_ERR(jz4780_rng->mem);
> +
> + platform_set_drvdata(pdev, jz4780_rng);
> + jz4780_rng_writel(jz4780_rng, 1, REG_RNG_CTRL);
> + ret = hwrng_register(&jz4780_rng->rng);
> +
> + return ret;
> +}
You could write directly return hwrng_register(..)
Regards
LABBE Corentin
