// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright 2013 Michael Ellerman, Guo Chao, IBM Corp.
 */

#define pr_fmt(fmt)     KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/random.h>
#include <linux/hw_random.h>
#include <asm/archrandom.h>

static int powernv_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
{
        unsigned long *buf;
        int i, len;

        /* We rely on rng_buffer_size() being >= sizeof(unsigned long) */
        len = max / sizeof(unsigned long);

        buf = (unsigned long *)data;

        for (i = 0; i < len; i++)
                pnv_get_random_long(buf++);

        return len * sizeof(unsigned long);
}

static struct hwrng powernv_hwrng = {
        .name = "powernv-rng",
        .read = powernv_rng_read,
};

static int powernv_rng_probe(struct platform_device *pdev)
{
        int rc;

        rc = devm_hwrng_register(&pdev->dev, &powernv_hwrng);
        if (rc) {
                /* We only register one device, ignore any others */
                if (rc == -EEXIST)
                        rc = -ENODEV;

                return rc;
        }

        pr_info("Registered powernv hwrng.\n");

        return 0;
}

static const struct of_device_id powernv_rng_match[] = {
        { .compatible   = "ibm,power-rng",},
        {},
};
MODULE_DEVICE_TABLE(of, powernv_rng_match);

static struct platform_driver powernv_rng_driver = {
        .driver = {
                .name = "powernv_rng",
                .of_match_table = powernv_rng_match,
        },
        .probe  = powernv_rng_probe,
};
module_platform_driver(powernv_rng_driver);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Bare metal HWRNG driver for POWER7+ and above");