1/*
  2 * Copyright (C) 2016 HiSilicon Co., Ltd.
  3 *
  4 * This program is free software; you can redistribute it and/or modify
  5 * it under the terms of the GNU General Public License version 2 as
  6 * published by the Free Software Foundation.
  7 */
  8
  9#include <linux/err.h>
 10#include <linux/kernel.h>
 11#include <linux/hw_random.h>
 12#include <linux/io.h>
 13#include <linux/module.h>
 14#include <linux/of.h>
 15#include <linux/platform_device.h>
 16#include <linux/random.h>
 17
 18#define RNG_SEED	0x0
 19#define RNG_CTRL	0x4
 20  #define RNG_SEED_SEL	BIT(2)
 21  #define RNG_RING_EN	BIT(1)
 22  #define RNG_EN	BIT(0)
 23#define RNG_RAN_NUM	0x10
 24#define RNG_PHY_SEED	0x14
 25
 26#define to_hisi_rng(p)	container_of(p, struct hisi_rng, rng)
 27
 28static int seed_sel;
 29module_param(seed_sel, int, S_IRUGO);
 30MODULE_PARM_DESC(seed_sel, "Auto reload seed. 0, use LFSR(default); 1, use ring oscillator.");
 31
 32struct hisi_rng {
 33	void __iomem *base;
 34	struct hwrng rng;
 35};
 36
 37static int hisi_rng_init(struct hwrng *rng)
 38{
 39	struct hisi_rng *hrng = to_hisi_rng(rng);
 40	int val = RNG_EN;
 41	u32 seed;
 42
 43	/* get a random number as initial seed */
 44	get_random_bytes(&seed, sizeof(seed));
 45
 46	writel_relaxed(seed, hrng->base + RNG_SEED);
 47
 48	/**
 49	 * The seed is reload periodically, there are two choice
 50	 * of seeds, default seed using the value from LFSR, or
 51	 * will use seed generated by ring oscillator.
 52	 */
 53	if (seed_sel == 1)
 54		val |= RNG_RING_EN | RNG_SEED_SEL;
 55
 56	writel_relaxed(val, hrng->base + RNG_CTRL);
 57	return 0;
 58}
 59
 60static void hisi_rng_cleanup(struct hwrng *rng)
 61{
 62	struct hisi_rng *hrng = to_hisi_rng(rng);
 63
 64	writel_relaxed(0, hrng->base + RNG_CTRL);
 65}
 66
 67static int hisi_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
 68{
 69	struct hisi_rng *hrng = to_hisi_rng(rng);
 70	u32 *data = buf;
 71
 72	*data = readl_relaxed(hrng->base + RNG_RAN_NUM);
 73	return 4;
 74}
 75
 76static int hisi_rng_probe(struct platform_device *pdev)
 77{
 78	struct hisi_rng *rng;
 79	struct resource *res;
 80	int ret;
 81
 82	rng = devm_kzalloc(&pdev->dev, sizeof(*rng), GFP_KERNEL);
 83	if (!rng)
 84		return -ENOMEM;
 85
 86	platform_set_drvdata(pdev, rng);
 87
 88	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 89	rng->base = devm_ioremap_resource(&pdev->dev, res);
 90	if (IS_ERR(rng->base))
 91		return PTR_ERR(rng->base);
 92
 93	rng->rng.name = pdev->name;
 94	rng->rng.init = hisi_rng_init;
 95	rng->rng.cleanup = hisi_rng_cleanup;
 96	rng->rng.read = hisi_rng_read;
 97
 98	ret = devm_hwrng_register(&pdev->dev, &rng->rng);
 99	if (ret) {
100		dev_err(&pdev->dev, "failed to register hwrng\n");
101		return ret;
102	}
103
104	return 0;
105}
106
107static const struct of_device_id hisi_rng_dt_ids[] = {
108	{ .compatible = "hisilicon,hip04-rng" },
109	{ .compatible = "hisilicon,hip05-rng" },
110	{ }
111};
112MODULE_DEVICE_TABLE(of, hisi_rng_dt_ids);
113
114static struct platform_driver hisi_rng_driver = {
115	.probe		= hisi_rng_probe,
116	.driver		= {
117		.name	= "hisi-rng",
118		.of_match_table = of_match_ptr(hisi_rng_dt_ids),
119	},
120};
121
122module_platform_driver(hisi_rng_driver);
123
124MODULE_LICENSE("GPL");
125MODULE_AUTHOR("Kefeng Wang <wangkefeng.wang@huawei>");
126MODULE_DESCRIPTION("Hisilicon random number generator driver");