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			int err;
 53
 54			err = readl_relaxed_poll_timeout_atomic(priv->base
 55								   + RNG_SR,
 56								   sr, sr,
 57								   10, 50000);
 58			if (err)
 59				dev_err((struct device *)priv->rng.priv,
 60					"%s: timeout %x!\n", __func__, sr);
 61		}
 62
 63		/* If error detected or data not ready... */
 64		if (sr != RNG_SR_DRDY) {
 65			if (WARN_ONCE(sr & (RNG_SR_SEIS | RNG_SR_CEIS),
 66					"bad RNG status - %x\n", sr))
 67				writel_relaxed(0, priv->base + RNG_SR);
 68			break;
 69		}
 70
 71		*(u32 *)data = readl_relaxed(priv->base + RNG_DR);
 72
 73		retval += sizeof(u32);
 74		data += sizeof(u32);
 75		max -= sizeof(u32);
 76	}
 77
 78	pm_runtime_mark_last_busy((struct device *) priv->rng.priv);
 79	pm_runtime_put_sync_autosuspend((struct device *) priv->rng.priv);
 80
 81	return retval || !wait ? retval : -EIO;
 82}
 83
 84static int stm32_rng_init(struct hwrng *rng)
 85{
 86	struct stm32_rng_private *priv =
 87	    container_of(rng, struct stm32_rng_private, rng);
 88	int err;
 89
 90	err = clk_prepare_enable(priv->clk);
 91	if (err)
 92		return err;
 93
 94	if (priv->ced)
 95		writel_relaxed(RNG_CR_RNGEN, priv->base + RNG_CR);
 96	else
 97		writel_relaxed(RNG_CR_RNGEN | RNG_CR_CED,
 98			       priv->base + RNG_CR);
 99
100	/* clear error indicators */
101	writel_relaxed(0, priv->base + RNG_SR);
102
103	return 0;
104}
105
106static void stm32_rng_cleanup(struct hwrng *rng)
107{
108	struct stm32_rng_private *priv =
109	    container_of(rng, struct stm32_rng_private, rng);
110
111	writel_relaxed(0, priv->base + RNG_CR);
112	clk_disable_unprepare(priv->clk);
113}
114
115static int stm32_rng_probe(struct platform_device *ofdev)
116{
117	struct device *dev = &ofdev->dev;
118	struct device_node *np = ofdev->dev.of_node;
119	struct stm32_rng_private *priv;
120	struct resource res;
121	int err;
122
123	priv = devm_kzalloc(dev, sizeof(struct stm32_rng_private), GFP_KERNEL);
124	if (!priv)
125		return -ENOMEM;
126
127	err = of_address_to_resource(np, 0, &res);
128	if (err)
129		return err;
130
131	priv->base = devm_ioremap_resource(dev, &res);
132	if (IS_ERR(priv->base))
133		return PTR_ERR(priv->base);
134
135	priv->clk = devm_clk_get(&ofdev->dev, NULL);
136	if (IS_ERR(priv->clk))
137		return PTR_ERR(priv->clk);
138
139	priv->rst = devm_reset_control_get(&ofdev->dev, NULL);
140	if (!IS_ERR(priv->rst)) {
141		reset_control_assert(priv->rst);
142		udelay(2);
143		reset_control_deassert(priv->rst);
144	}
145
146	priv->ced = of_property_read_bool(np, "clock-error-detect");
147
148	dev_set_drvdata(dev, priv);
149
150	priv->rng.name = dev_driver_string(dev);
151#ifndef CONFIG_PM
152	priv->rng.init = stm32_rng_init;
153	priv->rng.cleanup = stm32_rng_cleanup;
154#endif
155	priv->rng.read = stm32_rng_read;
156	priv->rng.priv = (unsigned long) dev;
157	priv->rng.quality = 900;
158
159	pm_runtime_set_autosuspend_delay(dev, 100);
160	pm_runtime_use_autosuspend(dev);
161	pm_runtime_enable(dev);
162
163	return devm_hwrng_register(dev, &priv->rng);
164}
165
166static int stm32_rng_remove(struct platform_device *ofdev)
167{
168	pm_runtime_disable(&ofdev->dev);
169
170	return 0;
171}
172
173#ifdef CONFIG_PM
174static int stm32_rng_runtime_suspend(struct device *dev)
175{
176	struct stm32_rng_private *priv = dev_get_drvdata(dev);
177
178	stm32_rng_cleanup(&priv->rng);
179
180	return 0;
181}
182
183static int stm32_rng_runtime_resume(struct device *dev)
184{
185	struct stm32_rng_private *priv = dev_get_drvdata(dev);
186
187	return stm32_rng_init(&priv->rng);
188}
189#endif
190
191static const struct dev_pm_ops stm32_rng_pm_ops = {
192	SET_RUNTIME_PM_OPS(stm32_rng_runtime_suspend,
193			   stm32_rng_runtime_resume, NULL)
194	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
195				pm_runtime_force_resume)
196};
197
198
199static const struct of_device_id stm32_rng_match[] = {
200	{
201		.compatible = "st,stm32-rng",
202	},
203	{},
204};
205MODULE_DEVICE_TABLE(of, stm32_rng_match);
206
207static struct platform_driver stm32_rng_driver = {
208	.driver = {
209		.name = "stm32-rng",
210		.pm = &stm32_rng_pm_ops,
211		.of_match_table = stm32_rng_match,
212	},
213	.probe = stm32_rng_probe,
214	.remove = stm32_rng_remove,
215};
216
217module_platform_driver(stm32_rng_driver);
218
219MODULE_LICENSE("GPL");
220MODULE_AUTHOR("Daniel Thompson <daniel.thompson@linaro.org>");
221MODULE_DESCRIPTION("STMicroelectronics STM32 RNG device driver");