1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * Copyright (c) 2015, Daniel Thompson
  4 */
  5
  6#include <linux/clk.h>
  7#include <linux/delay.h>
  8#include <linux/hw_random.h>
  9#include <linux/io.h>
 10#include <linux/iopoll.h>
 11#include <linux/kernel.h>
 12#include <linux/module.h>
 13#include <linux/of_address.h>
 14#include <linux/of_platform.h>
 15#include <linux/pm_runtime.h>
 16#include <linux/reset.h>
 17#include <linux/slab.h>
 18
 19#define RNG_CR 0x00
 20#define RNG_CR_RNGEN BIT(2)
 21#define RNG_CR_CED BIT(5)
 22
 23#define RNG_SR 0x04
 24#define RNG_SR_SEIS BIT(6)
 25#define RNG_SR_CEIS BIT(5)
 26#define RNG_SR_DRDY BIT(0)
 27
 28#define RNG_DR 0x08
 29
 30struct stm32_rng_private {
 31	struct hwrng rng;
 32	void __iomem *base;
 33	struct clk *clk;
 34	struct reset_control *rst;
 35	bool ced;
 36};
 37
 38static int stm32_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
 39{
 40	struct stm32_rng_private *priv =
 41	    container_of(rng, struct stm32_rng_private, rng);
 42	u32 sr;
 43	int retval = 0;
 44
 45	pm_runtime_get_sync((struct device *) priv->rng.priv);
 46
 47	while (max > sizeof(u32)) {
 48		sr = readl_relaxed(priv->base + RNG_SR);
 49		/* Manage timeout which is based on timer and take */
 50		/* care of initial delay time when enabling rng	*/
 51		if (!sr && wait) {
 52			retval = readl_relaxed_poll_timeout_atomic(priv->base
 53								   + RNG_SR,
 54								   sr, sr,
 55								   10, 50000);
 56			if (retval)
 57				dev_err((struct device *)priv->rng.priv,
 58					"%s: timeout %x!\n", __func__, sr);
 59		}
 60
 61		/* If error detected or data not ready... */
 62		if (sr != RNG_SR_DRDY) {
 63			if (WARN_ONCE(sr & (RNG_SR_SEIS | RNG_SR_CEIS),
 64					"bad RNG status - %x\n", sr))
 65				writel_relaxed(0, priv->base + RNG_SR);
 66			break;
 67		}
 68
 69		*(u32 *)data = readl_relaxed(priv->base + RNG_DR);
 70
 71		retval += sizeof(u32);
 72		data += sizeof(u32);
 73		max -= sizeof(u32);
 74	}
 75
 76	pm_runtime_mark_last_busy((struct device *) priv->rng.priv);
 77	pm_runtime_put_sync_autosuspend((struct device *) priv->rng.priv);
 78
 79	return retval || !wait ? retval : -EIO;
 80}
 81
 82static int stm32_rng_init(struct hwrng *rng)
 83{
 84	struct stm32_rng_private *priv =
 85	    container_of(rng, struct stm32_rng_private, rng);
 86	int err;
 87
 88	err = clk_prepare_enable(priv->clk);
 89	if (err)
 90		return err;
 91
 92	if (priv->ced)
 93		writel_relaxed(RNG_CR_RNGEN, priv->base + RNG_CR);
 94	else
 95		writel_relaxed(RNG_CR_RNGEN | RNG_CR_CED,
 96			       priv->base + RNG_CR);
 97
 98	/* clear error indicators */
 99	writel_relaxed(0, priv->base + RNG_SR);
100
101	return 0;
102}
103
104static void stm32_rng_cleanup(struct hwrng *rng)
105{
106	struct stm32_rng_private *priv =
107	    container_of(rng, struct stm32_rng_private, rng);
108
109	writel_relaxed(0, priv->base + RNG_CR);
110	clk_disable_unprepare(priv->clk);
111}
112
113static int stm32_rng_probe(struct platform_device *ofdev)
114{
115	struct device *dev = &ofdev->dev;
116	struct device_node *np = ofdev->dev.of_node;
117	struct stm32_rng_private *priv;
118	struct resource res;
119	int err;
120
121	priv = devm_kzalloc(dev, sizeof(struct stm32_rng_private), GFP_KERNEL);
122	if (!priv)
123		return -ENOMEM;
124
125	err = of_address_to_resource(np, 0, &res);
126	if (err)
127		return err;
128
129	priv->base = devm_ioremap_resource(dev, &res);
130	if (IS_ERR(priv->base))
131		return PTR_ERR(priv->base);
132
133	priv->clk = devm_clk_get(&ofdev->dev, NULL);
134	if (IS_ERR(priv->clk))
135		return PTR_ERR(priv->clk);
136
137	priv->rst = devm_reset_control_get(&ofdev->dev, NULL);
138	if (!IS_ERR(priv->rst)) {
139		reset_control_assert(priv->rst);
140		udelay(2);
141		reset_control_deassert(priv->rst);
142	}
143
144	priv->ced = of_property_read_bool(np, "clock-error-detect");
145
146	dev_set_drvdata(dev, priv);
147
148	priv->rng.name = dev_driver_string(dev);
149#ifndef CONFIG_PM
150	priv->rng.init = stm32_rng_init;
151	priv->rng.cleanup = stm32_rng_cleanup;
152#endif
153	priv->rng.read = stm32_rng_read;
154	priv->rng.priv = (unsigned long) dev;
155	priv->rng.quality = 900;
156
157	pm_runtime_set_autosuspend_delay(dev, 100);
158	pm_runtime_use_autosuspend(dev);
159	pm_runtime_enable(dev);
160
161	return devm_hwrng_register(dev, &priv->rng);
162}
163
164static int stm32_rng_remove(struct platform_device *ofdev)
165{
166	pm_runtime_disable(&ofdev->dev);
167
168	return 0;
169}
170
171#ifdef CONFIG_PM
172static int stm32_rng_runtime_suspend(struct device *dev)
173{
174	struct stm32_rng_private *priv = dev_get_drvdata(dev);
175
176	stm32_rng_cleanup(&priv->rng);
177
178	return 0;
179}
180
181static int stm32_rng_runtime_resume(struct device *dev)
182{
183	struct stm32_rng_private *priv = dev_get_drvdata(dev);
184
185	return stm32_rng_init(&priv->rng);
186}
187#endif
188
189static const struct dev_pm_ops stm32_rng_pm_ops = {
190	SET_RUNTIME_PM_OPS(stm32_rng_runtime_suspend,
191			   stm32_rng_runtime_resume, NULL)
192	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
193				pm_runtime_force_resume)
194};
195
196
197static const struct of_device_id stm32_rng_match[] = {
198	{
199		.compatible = "st,stm32-rng",
200	},
201	{},
202};
203MODULE_DEVICE_TABLE(of, stm32_rng_match);
204
205static struct platform_driver stm32_rng_driver = {
206	.driver = {
207		.name = "stm32-rng",
208		.pm = &stm32_rng_pm_ops,
209		.of_match_table = stm32_rng_match,
210	},
211	.probe = stm32_rng_probe,
212	.remove = stm32_rng_remove,
213};
214
215module_platform_driver(stm32_rng_driver);
216
217MODULE_LICENSE("GPL");
218MODULE_AUTHOR("Daniel Thompson <daniel.thompson@linaro.org>");
219MODULE_DESCRIPTION("STMicroelectronics STM32 RNG device driver");