1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Random Number Generator driver for the Keystone SOC
4  *
5  * Copyright (C) 2016 Texas Instruments Incorporated - https://www.ti.com
6  *
7  * Authors:	Sandeep Nair
8  *		Vitaly Andrianov
9  */
10 
11 #include <linux/hw_random.h>
12 #include <linux/kernel.h>
13 #include <linux/module.h>
14 #include <linux/io.h>
15 #include <linux/platform_device.h>
16 #include <linux/clk.h>
17 #include <linux/pm_runtime.h>
18 #include <linux/err.h>
19 #include <linux/regmap.h>
20 #include <linux/mfd/syscon.h>
21 #include <linux/of.h>
22 #include <linux/of_address.h>
23 #include <linux/delay.h>
24 #include <linux/timekeeping.h>
25 
26 #define SA_CMD_STATUS_OFS			0x8
27 
28 /* TRNG enable control in SA System module*/
29 #define SA_CMD_STATUS_REG_TRNG_ENABLE		BIT(3)
30 
31 /* TRNG start control in TRNG module */
32 #define TRNG_CNTL_REG_TRNG_ENABLE		BIT(10)
33 
34 /* Data ready indicator in STATUS register */
35 #define TRNG_STATUS_REG_READY			BIT(0)
36 
37 /* Data ready clear control in INTACK register */
38 #define TRNG_INTACK_REG_READY			BIT(0)
39 
40 /*
41  * Number of samples taken to gather entropy during startup.
42  * If value is 0, the number of samples is 2^24 else
43  * equals value times 2^8.
44  */
45 #define TRNG_DEF_STARTUP_CYCLES			0
46 #define TRNG_CNTL_REG_STARTUP_CYCLES_SHIFT	16
47 
48 /*
49  * Minimum number of samples taken to regenerate entropy
50  * If value is 0, the number of samples is 2^24 else
51  * equals value times 2^6.
52  */
53 #define TRNG_DEF_MIN_REFILL_CYCLES		1
54 #define TRNG_CFG_REG_MIN_REFILL_CYCLES_SHIFT	0
55 
56 /*
57  * Maximum number of samples taken to regenerate entropy
58  * If value is 0, the number of samples is 2^24 else
59  * equals value times 2^8.
60  */
61 #define TRNG_DEF_MAX_REFILL_CYCLES		0
62 #define TRNG_CFG_REG_MAX_REFILL_CYCLES_SHIFT	16
63 
64 /* Number of CLK input cycles between samples */
65 #define TRNG_DEF_CLK_DIV_CYCLES			0
66 #define TRNG_CFG_REG_SAMPLE_DIV_SHIFT		8
67 
68 /* Maximum retries to get rng data */
69 #define SA_MAX_RNG_DATA_RETRIES			5
70 /* Delay between retries (in usecs) */
71 #define SA_RNG_DATA_RETRY_DELAY			5
72 
73 struct trng_regs {
74 	u32	output_l;
75 	u32	output_h;
76 	u32	status;
77 	u32	intmask;
78 	u32	intack;
79 	u32	control;
80 	u32	config;
81 };
82 
83 struct ks_sa_rng {
84 	struct device	*dev;
85 	struct hwrng	rng;
86 	struct clk	*clk;
87 	struct regmap	*regmap_cfg;
88 	struct trng_regs __iomem *reg_rng;
89 	u64 ready_ts;
90 	unsigned int refill_delay_ns;
91 };
92 
93 static unsigned int cycles_to_ns(unsigned long clk_rate, unsigned int cycles)
94 {
95 	return DIV_ROUND_UP_ULL((TRNG_DEF_CLK_DIV_CYCLES + 1) * 1000000000ull *
96 				cycles, clk_rate);
97 }
98 
99 static unsigned int startup_delay_ns(unsigned long clk_rate)
100 {
101 	if (!TRNG_DEF_STARTUP_CYCLES)
102 		return cycles_to_ns(clk_rate, BIT(24));
103 	return cycles_to_ns(clk_rate, 256 * TRNG_DEF_STARTUP_CYCLES);
104 }
105 
106 static unsigned int refill_delay_ns(unsigned long clk_rate)
107 {
108 	if (!TRNG_DEF_MAX_REFILL_CYCLES)
109 		return cycles_to_ns(clk_rate, BIT(24));
110 	return cycles_to_ns(clk_rate, 256 * TRNG_DEF_MAX_REFILL_CYCLES);
111 }
112 
113 static int ks_sa_rng_init(struct hwrng *rng)
114 {
115 	u32 value;
116 	struct device *dev = (struct device *)rng->priv;
117 	struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);
118 	unsigned long clk_rate = clk_get_rate(ks_sa_rng->clk);
119 
120 	/* Enable RNG module */
121 	regmap_write_bits(ks_sa_rng->regmap_cfg, SA_CMD_STATUS_OFS,
122 			  SA_CMD_STATUS_REG_TRNG_ENABLE,
123 			  SA_CMD_STATUS_REG_TRNG_ENABLE);
124 
125 	/* Configure RNG module */
126 	writel(0, &ks_sa_rng->reg_rng->control);
127 	value = TRNG_DEF_STARTUP_CYCLES << TRNG_CNTL_REG_STARTUP_CYCLES_SHIFT;
128 	writel(value, &ks_sa_rng->reg_rng->control);
129 
130 	value =	(TRNG_DEF_MIN_REFILL_CYCLES <<
131 		 TRNG_CFG_REG_MIN_REFILL_CYCLES_SHIFT) |
132 		(TRNG_DEF_MAX_REFILL_CYCLES <<
133 		 TRNG_CFG_REG_MAX_REFILL_CYCLES_SHIFT) |
134 		(TRNG_DEF_CLK_DIV_CYCLES <<
135 		 TRNG_CFG_REG_SAMPLE_DIV_SHIFT);
136 
137 	writel(value, &ks_sa_rng->reg_rng->config);
138 
139 	/* Disable all interrupts from TRNG */
140 	writel(0, &ks_sa_rng->reg_rng->intmask);
141 
142 	/* Enable RNG */
143 	value = readl(&ks_sa_rng->reg_rng->control);
144 	value |= TRNG_CNTL_REG_TRNG_ENABLE;
145 	writel(value, &ks_sa_rng->reg_rng->control);
146 
147 	ks_sa_rng->refill_delay_ns = refill_delay_ns(clk_rate);
148 	ks_sa_rng->ready_ts = ktime_get_ns() +
149 			      startup_delay_ns(clk_rate);
150 
151 	return 0;
152 }
153 
154 static void ks_sa_rng_cleanup(struct hwrng *rng)
155 {
156 	struct device *dev = (struct device *)rng->priv;
157 	struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);
158 
159 	/* Disable RNG */
160 	writel(0, &ks_sa_rng->reg_rng->control);
161 	regmap_write_bits(ks_sa_rng->regmap_cfg, SA_CMD_STATUS_OFS,
162 			  SA_CMD_STATUS_REG_TRNG_ENABLE, 0);
163 }
164 
165 static int ks_sa_rng_data_read(struct hwrng *rng, u32 *data)
166 {
167 	struct device *dev = (struct device *)rng->priv;
168 	struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);
169 
170 	/* Read random data */
171 	data[0] = readl(&ks_sa_rng->reg_rng->output_l);
172 	data[1] = readl(&ks_sa_rng->reg_rng->output_h);
173 
174 	writel(TRNG_INTACK_REG_READY, &ks_sa_rng->reg_rng->intack);
175 	ks_sa_rng->ready_ts = ktime_get_ns() + ks_sa_rng->refill_delay_ns;
176 
177 	return sizeof(u32) * 2;
178 }
179 
180 static int ks_sa_rng_data_present(struct hwrng *rng, int wait)
181 {
182 	struct device *dev = (struct device *)rng->priv;
183 	struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);
184 	u64 now = ktime_get_ns();
185 
186 	u32	ready;
187 	int	j;
188 
189 	if (wait && now < ks_sa_rng->ready_ts) {
190 		/* Max delay expected here is 81920000 ns */
191 		unsigned long min_delay =
192 			DIV_ROUND_UP((u32)(ks_sa_rng->ready_ts - now), 1000);
193 
194 		usleep_range(min_delay, min_delay + SA_RNG_DATA_RETRY_DELAY);
195 	}
196 
197 	for (j = 0; j < SA_MAX_RNG_DATA_RETRIES; j++) {
198 		ready = readl(&ks_sa_rng->reg_rng->status);
199 		ready &= TRNG_STATUS_REG_READY;
200 
201 		if (ready || !wait)
202 			break;
203 
204 		udelay(SA_RNG_DATA_RETRY_DELAY);
205 	}
206 
207 	return ready;
208 }
209 
210 static int ks_sa_rng_probe(struct platform_device *pdev)
211 {
212 	struct ks_sa_rng	*ks_sa_rng;
213 	struct device		*dev = &pdev->dev;
214 	int			ret;
215 
216 	ks_sa_rng = devm_kzalloc(dev, sizeof(*ks_sa_rng), GFP_KERNEL);
217 	if (!ks_sa_rng)
218 		return -ENOMEM;
219 
220 	ks_sa_rng->dev = dev;
221 	ks_sa_rng->rng = (struct hwrng) {
222 		.name = "ks_sa_hwrng",
223 		.init = ks_sa_rng_init,
224 		.data_read = ks_sa_rng_data_read,
225 		.data_present = ks_sa_rng_data_present,
226 		.cleanup = ks_sa_rng_cleanup,
227 	};
228 	ks_sa_rng->rng.priv = (unsigned long)dev;
229 
230 	ks_sa_rng->reg_rng = devm_platform_ioremap_resource(pdev, 0);
231 	if (IS_ERR(ks_sa_rng->reg_rng))
232 		return PTR_ERR(ks_sa_rng->reg_rng);
233 
234 	ks_sa_rng->regmap_cfg =
235 		syscon_regmap_lookup_by_phandle(dev->of_node,
236 						"ti,syscon-sa-cfg");
237 
238 	if (IS_ERR(ks_sa_rng->regmap_cfg)) {
239 		dev_err(dev, "syscon_node_to_regmap failed\n");
240 		return -EINVAL;
241 	}
242 
243 	pm_runtime_enable(dev);
244 	ret = pm_runtime_resume_and_get(dev);
245 	if (ret < 0) {
246 		dev_err(dev, "Failed to enable SA power-domain\n");
247 		pm_runtime_disable(dev);
248 		return ret;
249 	}
250 
251 	platform_set_drvdata(pdev, ks_sa_rng);
252 
253 	return devm_hwrng_register(&pdev->dev, &ks_sa_rng->rng);
254 }
255 
256 static int ks_sa_rng_remove(struct platform_device *pdev)
257 {
258 	pm_runtime_put_sync(&pdev->dev);
259 	pm_runtime_disable(&pdev->dev);
260 
261 	return 0;
262 }
263 
264 static const struct of_device_id ks_sa_rng_dt_match[] = {
265 	{
266 		.compatible = "ti,keystone-rng",
267 	},
268 	{ },
269 };
270 MODULE_DEVICE_TABLE(of, ks_sa_rng_dt_match);
271 
272 static struct platform_driver ks_sa_rng_driver = {
273 	.driver		= {
274 		.name	= "ks-sa-rng",
275 		.of_match_table = ks_sa_rng_dt_match,
276 	},
277 	.probe		= ks_sa_rng_probe,
278 	.remove		= ks_sa_rng_remove,
279 };
280 
281 module_platform_driver(ks_sa_rng_driver);
282 
283 MODULE_DESCRIPTION("Keystone NETCP SA H/W Random Number Generator driver");
284 MODULE_AUTHOR("Vitaly Andrianov <vitalya@ti.com>");
285 MODULE_LICENSE("GPL");
286