1/*
  2 * Copyright (c) 2011-2013, The Linux Foundation. All rights reserved.
  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 and
  6 * only version 2 as published by the Free Software Foundation.
  7 *
  8 * This program is distributed in the hope that it will be useful,
  9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 11 * GNU General Public License for more details.
 12 *
 13 */
 14#include <linux/clk.h>
 15#include <linux/err.h>
 16#include <linux/hw_random.h>
 17#include <linux/io.h>
 18#include <linux/module.h>
 19#include <linux/of.h>
 20#include <linux/platform_device.h>
 21
 22/* Device specific register offsets */
 23#define PRNG_DATA_OUT		0x0000
 24#define PRNG_STATUS		0x0004
 25#define PRNG_LFSR_CFG		0x0100
 26#define PRNG_CONFIG		0x0104
 27
 28/* Device specific register masks and config values */
 29#define PRNG_LFSR_CFG_MASK	0x0000ffff
 30#define PRNG_LFSR_CFG_CLOCKS	0x0000dddd
 31#define PRNG_CONFIG_HW_ENABLE	BIT(1)
 32#define PRNG_STATUS_DATA_AVAIL	BIT(0)
 33
 34#define MAX_HW_FIFO_DEPTH	16
 35#define MAX_HW_FIFO_SIZE	(MAX_HW_FIFO_DEPTH * 4)
 36#define WORD_SZ			4
 37
 38struct msm_rng {
 39	void __iomem *base;
 40	struct clk *clk;
 41	struct hwrng hwrng;
 42};
 43
 44#define to_msm_rng(p)	container_of(p, struct msm_rng, hwrng)
 45
 46static int msm_rng_enable(struct hwrng *hwrng, int enable)
 47{
 48	struct msm_rng *rng = to_msm_rng(hwrng);
 49	u32 val;
 50	int ret;
 51
 52	ret = clk_prepare_enable(rng->clk);
 53	if (ret)
 54		return ret;
 55
 56	if (enable) {
 57		/* Enable PRNG only if it is not already enabled */
 58		val = readl_relaxed(rng->base + PRNG_CONFIG);
 59		if (val & PRNG_CONFIG_HW_ENABLE)
 60			goto already_enabled;
 61
 62		val = readl_relaxed(rng->base + PRNG_LFSR_CFG);
 63		val &= ~PRNG_LFSR_CFG_MASK;
 64		val |= PRNG_LFSR_CFG_CLOCKS;
 65		writel(val, rng->base + PRNG_LFSR_CFG);
 66
 67		val = readl_relaxed(rng->base + PRNG_CONFIG);
 68		val |= PRNG_CONFIG_HW_ENABLE;
 69		writel(val, rng->base + PRNG_CONFIG);
 70	} else {
 71		val = readl_relaxed(rng->base + PRNG_CONFIG);
 72		val &= ~PRNG_CONFIG_HW_ENABLE;
 73		writel(val, rng->base + PRNG_CONFIG);
 74	}
 75
 76already_enabled:
 77	clk_disable_unprepare(rng->clk);
 78	return 0;
 79}
 80
 81static int msm_rng_read(struct hwrng *hwrng, void *data, size_t max, bool wait)
 82{
 83	struct msm_rng *rng = to_msm_rng(hwrng);
 84	size_t currsize = 0;
 85	u32 *retdata = data;
 86	size_t maxsize;
 87	int ret;
 88	u32 val;
 89
 90	/* calculate max size bytes to transfer back to caller */
 91	maxsize = min_t(size_t, MAX_HW_FIFO_SIZE, max);
 92
 93	/* no room for word data */
 94	if (maxsize < WORD_SZ)
 95		return 0;
 96
 97	ret = clk_prepare_enable(rng->clk);
 98	if (ret)
 99		return ret;
100
101	/* read random data from hardware */
102	do {
103		val = readl_relaxed(rng->base + PRNG_STATUS);
104		if (!(val & PRNG_STATUS_DATA_AVAIL))
105			break;
106
107		val = readl_relaxed(rng->base + PRNG_DATA_OUT);
108		if (!val)
109			break;
110
111		*retdata++ = val;
112		currsize += WORD_SZ;
113
114		/* make sure we stay on 32bit boundary */
115		if ((maxsize - currsize) < WORD_SZ)
116			break;
117	} while (currsize < maxsize);
118
119	clk_disable_unprepare(rng->clk);
120
121	return currsize;
122}
123
124static int msm_rng_init(struct hwrng *hwrng)
125{
126	return msm_rng_enable(hwrng, 1);
127}
128
129static void msm_rng_cleanup(struct hwrng *hwrng)
130{
131	msm_rng_enable(hwrng, 0);
132}
133
134static int msm_rng_probe(struct platform_device *pdev)
135{
136	struct resource *res;
137	struct msm_rng *rng;
138	int ret;
139
140	rng = devm_kzalloc(&pdev->dev, sizeof(*rng), GFP_KERNEL);
141	if (!rng)
142		return -ENOMEM;
143
144	platform_set_drvdata(pdev, rng);
145
146	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
147	rng->base = devm_ioremap_resource(&pdev->dev, res);
148	if (IS_ERR(rng->base))
149		return PTR_ERR(rng->base);
150
151	rng->clk = devm_clk_get(&pdev->dev, "core");
152	if (IS_ERR(rng->clk))
153		return PTR_ERR(rng->clk);
154
155	rng->hwrng.name = KBUILD_MODNAME,
156	rng->hwrng.init = msm_rng_init,
157	rng->hwrng.cleanup = msm_rng_cleanup,
158	rng->hwrng.read = msm_rng_read,
159
160	ret = hwrng_register(&rng->hwrng);
161	if (ret) {
162		dev_err(&pdev->dev, "failed to register hwrng\n");
163		return ret;
164	}
165
166	return 0;
167}
168
169static int msm_rng_remove(struct platform_device *pdev)
170{
171	struct msm_rng *rng = platform_get_drvdata(pdev);
172
173	hwrng_unregister(&rng->hwrng);
174	return 0;
175}
176
177static const struct of_device_id msm_rng_of_match[] = {
178	{ .compatible = "qcom,prng", },
179	{}
180};
181MODULE_DEVICE_TABLE(of, msm_rng_of_match);
182
183static struct platform_driver msm_rng_driver = {
184	.probe = msm_rng_probe,
185	.remove = msm_rng_remove,
186	.driver = {
187		.name = KBUILD_MODNAME,
188		.owner = THIS_MODULE,
189		.of_match_table = of_match_ptr(msm_rng_of_match),
190	}
191};
192module_platform_driver(msm_rng_driver);
193
194MODULE_ALIAS("platform:" KBUILD_MODNAME);
195MODULE_AUTHOR("The Linux Foundation");
196MODULE_DESCRIPTION("Qualcomm MSM random number generator driver");
197MODULE_LICENSE("GPL v2");