1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * RNG driver for Freescale RNGC
4 *
5 * Copyright (C) 2008-2012 Freescale Semiconductor, Inc.
6 * Copyright (C) 2017 Martin Kaiser <martin@kaiser.cx>
7 */
8
9#include <linux/module.h>
10#include <linux/mod_devicetable.h>
11#include <linux/init.h>
12#include <linux/kernel.h>
13#include <linux/clk.h>
14#include <linux/err.h>
15#include <linux/platform_device.h>
16#include <linux/interrupt.h>
17#include <linux/hw_random.h>
18#include <linux/completion.h>
19#include <linux/io.h>
20#include <linux/bitfield.h>
21
22#define RNGC_VER_ID			0x0000
23#define RNGC_COMMAND			0x0004
24#define RNGC_CONTROL			0x0008
25#define RNGC_STATUS			0x000C
26#define RNGC_ERROR			0x0010
27#define RNGC_FIFO			0x0014
28
29/* the fields in the ver id register */
30#define RNG_TYPE			GENMASK(31, 28)
31#define RNGC_VER_MAJ_SHIFT		8
32
33/* the rng_type field */
34#define RNGC_TYPE_RNGB			0x1
35#define RNGC_TYPE_RNGC			0x2
36
37
38#define RNGC_CMD_CLR_ERR		BIT(5)
39#define RNGC_CMD_CLR_INT		BIT(4)
40#define RNGC_CMD_SEED			BIT(1)
41#define RNGC_CMD_SELF_TEST		BIT(0)
42
43#define RNGC_CTRL_MASK_ERROR		BIT(6)
44#define RNGC_CTRL_MASK_DONE		BIT(5)
45#define RNGC_CTRL_AUTO_SEED		BIT(4)
46
47#define RNGC_STATUS_ERROR		BIT(16)
48#define RNGC_STATUS_FIFO_LEVEL_MASK	GENMASK(11, 8)
49#define RNGC_STATUS_SEED_DONE		BIT(5)
50#define RNGC_STATUS_ST_DONE		BIT(4)
51
52#define RNGC_ERROR_STATUS_STAT_ERR	0x00000008
53
54#define RNGC_SELFTEST_TIMEOUT 2500 /* us */
55#define RNGC_SEED_TIMEOUT      200 /* ms */
56
57static bool self_test = true;
58module_param(self_test, bool, 0);
59
60struct imx_rngc {
61	struct device		*dev;
62	struct clk		*clk;
63	void __iomem		*base;
64	struct hwrng		rng;
65	struct completion	rng_op_done;
66	/*
67	 * err_reg is written only by the irq handler and read only
68	 * when interrupts are masked, we need no spinlock
69	 */
70	u32			err_reg;
71};
72
73
74static inline void imx_rngc_irq_mask_clear(struct imx_rngc *rngc)
75{
76	u32 ctrl, cmd;
77
78	/* mask interrupts */
79	ctrl = readl(rngc->base + RNGC_CONTROL);
80	ctrl |= RNGC_CTRL_MASK_DONE | RNGC_CTRL_MASK_ERROR;
81	writel(ctrl, rngc->base + RNGC_CONTROL);
82
83	/*
84	 * CLR_INT clears the interrupt only if there's no error
85	 * CLR_ERR clear the interrupt and the error register if there
86	 * is an error
87	 */
88	cmd = readl(rngc->base + RNGC_COMMAND);
89	cmd |= RNGC_CMD_CLR_INT | RNGC_CMD_CLR_ERR;
90	writel(cmd, rngc->base + RNGC_COMMAND);
91}
92
93static inline void imx_rngc_irq_unmask(struct imx_rngc *rngc)
94{
95	u32 ctrl;
96
97	ctrl = readl(rngc->base + RNGC_CONTROL);
98	ctrl &= ~(RNGC_CTRL_MASK_DONE | RNGC_CTRL_MASK_ERROR);
99	writel(ctrl, rngc->base + RNGC_CONTROL);
100}
101
102static int imx_rngc_self_test(struct imx_rngc *rngc)
103{
104	u32 cmd;
105	int ret;
106
107	imx_rngc_irq_unmask(rngc);
108
109	/* run self test */
110	cmd = readl(rngc->base + RNGC_COMMAND);
111	writel(cmd | RNGC_CMD_SELF_TEST, rngc->base + RNGC_COMMAND);
112
113	ret = wait_for_completion_timeout(&rngc->rng_op_done,
114					  usecs_to_jiffies(RNGC_SELFTEST_TIMEOUT));
115	imx_rngc_irq_mask_clear(rngc);
116	if (!ret)
117		return -ETIMEDOUT;
118
119	return rngc->err_reg ? -EIO : 0;
120}
121
122static int imx_rngc_read(struct hwrng *rng, void *data, size_t max, bool wait)
123{
124	struct imx_rngc *rngc = container_of(rng, struct imx_rngc, rng);
125	unsigned int status;
126	int retval = 0;
127
128	while (max >= sizeof(u32)) {
129		status = readl(rngc->base + RNGC_STATUS);
130
131		/* is there some error while reading this random number? */
132		if (status & RNGC_STATUS_ERROR)
133			break;
134
135		if (status & RNGC_STATUS_FIFO_LEVEL_MASK) {
136			/* retrieve a random number from FIFO */
137			*(u32 *)data = readl(rngc->base + RNGC_FIFO);
138
139			retval += sizeof(u32);
140			data += sizeof(u32);
141			max -= sizeof(u32);
142		}
143	}
144
145	return retval ? retval : -EIO;
146}
147
148static irqreturn_t imx_rngc_irq(int irq, void *priv)
149{
150	struct imx_rngc *rngc = (struct imx_rngc *)priv;
151	u32 status;
152
153	/*
154	 * clearing the interrupt will also clear the error register
155	 * read error and status before clearing
156	 */
157	status = readl(rngc->base + RNGC_STATUS);
158	rngc->err_reg = readl(rngc->base + RNGC_ERROR);
159
160	imx_rngc_irq_mask_clear(rngc);
161
162	if (status & (RNGC_STATUS_SEED_DONE | RNGC_STATUS_ST_DONE))
163		complete(&rngc->rng_op_done);
164
165	return IRQ_HANDLED;
166}
167
168static int imx_rngc_init(struct hwrng *rng)
169{
170	struct imx_rngc *rngc = container_of(rng, struct imx_rngc, rng);
171	u32 cmd, ctrl;
172	int ret;
173
174	/* clear error */
175	cmd = readl(rngc->base + RNGC_COMMAND);
176	writel(cmd | RNGC_CMD_CLR_ERR, rngc->base + RNGC_COMMAND);
177
178	imx_rngc_irq_unmask(rngc);
179
180	/* create seed, repeat while there is some statistical error */
181	do {
182		/* seed creation */
183		cmd = readl(rngc->base + RNGC_COMMAND);
184		writel(cmd | RNGC_CMD_SEED, rngc->base + RNGC_COMMAND);
185
186		ret = wait_for_completion_timeout(&rngc->rng_op_done,
187						  msecs_to_jiffies(RNGC_SEED_TIMEOUT));
188		if (!ret) {
189			ret = -ETIMEDOUT;
190			goto err;
191		}
192
193	} while (rngc->err_reg == RNGC_ERROR_STATUS_STAT_ERR);
194
195	if (rngc->err_reg) {
196		ret = -EIO;
197		goto err;
198	}
199
200	/*
201	 * enable automatic seeding, the rngc creates a new seed automatically
202	 * after serving 2^20 random 160-bit words
203	 */
204	ctrl = readl(rngc->base + RNGC_CONTROL);
205	ctrl |= RNGC_CTRL_AUTO_SEED;
206	writel(ctrl, rngc->base + RNGC_CONTROL);
207
208	/*
209	 * if initialisation was successful, we keep the interrupt
210	 * unmasked until imx_rngc_cleanup is called
211	 * we mask the interrupt ourselves if we return an error
212	 */
213	return 0;
214
215err:
216	imx_rngc_irq_mask_clear(rngc);
217	return ret;
218}
219
220static void imx_rngc_cleanup(struct hwrng *rng)
221{
222	struct imx_rngc *rngc = container_of(rng, struct imx_rngc, rng);
223
224	imx_rngc_irq_mask_clear(rngc);
225}
226
227static int __init imx_rngc_probe(struct platform_device *pdev)
228{
229	struct imx_rngc *rngc;
230	int ret;
231	int irq;
232	u32 ver_id;
233	u8  rng_type;
234
235	rngc = devm_kzalloc(&pdev->dev, sizeof(*rngc), GFP_KERNEL);
236	if (!rngc)
237		return -ENOMEM;
238
239	rngc->base = devm_platform_ioremap_resource(pdev, 0);
240	if (IS_ERR(rngc->base))
241		return PTR_ERR(rngc->base);
242
243	rngc->clk = devm_clk_get_enabled(&pdev->dev, NULL);
244	if (IS_ERR(rngc->clk))
245		return dev_err_probe(&pdev->dev, PTR_ERR(rngc->clk), "Cannot get rng_clk\n");
246
247	irq = platform_get_irq(pdev, 0);
248	if (irq < 0)
249		return irq;
250
251	ver_id = readl(rngc->base + RNGC_VER_ID);
252	rng_type = FIELD_GET(RNG_TYPE, ver_id);
253	/*
254	 * This driver supports only RNGC and RNGB. (There's a different
255	 * driver for RNGA.)
256	 */
257	if (rng_type != RNGC_TYPE_RNGC && rng_type != RNGC_TYPE_RNGB)
258		return -ENODEV;
259
260	init_completion(&rngc->rng_op_done);
261
262	rngc->rng.name = pdev->name;
263	rngc->rng.init = imx_rngc_init;
264	rngc->rng.read = imx_rngc_read;
265	rngc->rng.cleanup = imx_rngc_cleanup;
266	rngc->rng.quality = 19;
267
268	rngc->dev = &pdev->dev;
269	platform_set_drvdata(pdev, rngc);
270
271	imx_rngc_irq_mask_clear(rngc);
272
273	ret = devm_request_irq(&pdev->dev,
274			irq, imx_rngc_irq, 0, pdev->name, (void *)rngc);
275	if (ret)
276		return dev_err_probe(&pdev->dev, ret, "Can't get interrupt working.\n");
277
278	if (self_test) {
279		ret = imx_rngc_self_test(rngc);
280		if (ret)
281			return dev_err_probe(&pdev->dev, ret, "self test failed\n");
282	}
283
284	ret = devm_hwrng_register(&pdev->dev, &rngc->rng);
285	if (ret)
286		return dev_err_probe(&pdev->dev, ret, "hwrng registration failed\n");
287
288	dev_info(&pdev->dev,
289		"Freescale RNG%c registered (HW revision %d.%02d)\n",
290		rng_type == RNGC_TYPE_RNGB ? 'B' : 'C',
291		(ver_id >> RNGC_VER_MAJ_SHIFT) & 0xff, ver_id & 0xff);
292	return 0;
293}
294
295static int imx_rngc_suspend(struct device *dev)
296{
297	struct imx_rngc *rngc = dev_get_drvdata(dev);
298
299	clk_disable_unprepare(rngc->clk);
300
301	return 0;
302}
303
304static int imx_rngc_resume(struct device *dev)
305{
306	struct imx_rngc *rngc = dev_get_drvdata(dev);
307
308	clk_prepare_enable(rngc->clk);
309
310	return 0;
311}
312
313static DEFINE_SIMPLE_DEV_PM_OPS(imx_rngc_pm_ops, imx_rngc_suspend, imx_rngc_resume);
314
315static const struct of_device_id imx_rngc_dt_ids[] = {
316	{ .compatible = "fsl,imx25-rngb" },
317	{ /* sentinel */ }
318};
319MODULE_DEVICE_TABLE(of, imx_rngc_dt_ids);
320
321static struct platform_driver imx_rngc_driver = {
322	.driver = {
323		.name = KBUILD_MODNAME,
324		.pm = pm_sleep_ptr(&imx_rngc_pm_ops),
325		.of_match_table = imx_rngc_dt_ids,
326	},
327};
328
329module_platform_driver_probe(imx_rngc_driver, imx_rngc_probe);
330
331MODULE_AUTHOR("Freescale Semiconductor, Inc.");
332MODULE_DESCRIPTION("H/W RNGC driver for i.MX");
333MODULE_LICENSE("GPL");
334