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 - http://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 
25 #define SA_CMD_STATUS_OFS			0x8
26 
27 /* TRNG enable control in SA System module*/
28 #define SA_CMD_STATUS_REG_TRNG_ENABLE		BIT(3)
29 
30 /* TRNG start control in TRNG module */
31 #define TRNG_CNTL_REG_TRNG_ENABLE		BIT(10)
32 
33 /* Data ready indicator in STATUS register */
34 #define TRNG_STATUS_REG_READY			BIT(0)
35 
36 /* Data ready clear control in INTACK register */
37 #define TRNG_INTACK_REG_READY			BIT(0)
38 
39 /*
40  * Number of samples taken to gather entropy during startup.
41  * If value is 0, the number of samples is 2^24 else
42  * equals value times 2^8.
43  */
44 #define TRNG_DEF_STARTUP_CYCLES			0
45 #define TRNG_CNTL_REG_STARTUP_CYCLES_SHIFT	16
46 
47 /*
48  * Minimum number of samples taken to regenerate entropy
49  * If value is 0, the number of samples is 2^24 else
50  * equals value times 2^6.
51  */
52 #define TRNG_DEF_MIN_REFILL_CYCLES		1
53 #define TRNG_CFG_REG_MIN_REFILL_CYCLES_SHIFT	0
54 
55 /*
56  * Maximum number of samples taken to regenerate entropy
57  * If value is 0, the number of samples is 2^24 else
58  * equals value times 2^8.
59  */
60 #define TRNG_DEF_MAX_REFILL_CYCLES		0
61 #define TRNG_CFG_REG_MAX_REFILL_CYCLES_SHIFT	16
62 
63 /* Number of CLK input cycles between samples */
64 #define TRNG_DEF_CLK_DIV_CYCLES			0
65 #define TRNG_CFG_REG_SAMPLE_DIV_SHIFT		8
66 
67 /* Maximum retries to get rng data */
68 #define SA_MAX_RNG_DATA_RETRIES			5
69 /* Delay between retries (in usecs) */
70 #define SA_RNG_DATA_RETRY_DELAY			5
71 
72 struct trng_regs {
73 	u32	output_l;
74 	u32	output_h;
75 	u32	status;
76 	u32	intmask;
77 	u32	intack;
78 	u32	control;
79 	u32	config;
80 };
81 
82 struct ks_sa_rng {
83 	struct device	*dev;
84 	struct hwrng	rng;
85 	struct clk	*clk;
86 	struct regmap	*regmap_cfg;
87 	struct trng_regs *reg_rng;
88 };
89 
90 static int ks_sa_rng_init(struct hwrng *rng)
91 {
92 	u32 value;
93 	struct device *dev = (struct device *)rng->priv;
94 	struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);
95 
96 	/* Enable RNG module */
97 	regmap_write_bits(ks_sa_rng->regmap_cfg, SA_CMD_STATUS_OFS,
98 			  SA_CMD_STATUS_REG_TRNG_ENABLE,
99 			  SA_CMD_STATUS_REG_TRNG_ENABLE);
100 
101 	/* Configure RNG module */
102 	writel(0, &ks_sa_rng->reg_rng->control);
103 	value = TRNG_DEF_STARTUP_CYCLES << TRNG_CNTL_REG_STARTUP_CYCLES_SHIFT;
104 	writel(value, &ks_sa_rng->reg_rng->control);
105 
106 	value =	(TRNG_DEF_MIN_REFILL_CYCLES <<
107 		 TRNG_CFG_REG_MIN_REFILL_CYCLES_SHIFT) |
108 		(TRNG_DEF_MAX_REFILL_CYCLES <<
109 		 TRNG_CFG_REG_MAX_REFILL_CYCLES_SHIFT) |
110 		(TRNG_DEF_CLK_DIV_CYCLES <<
111 		 TRNG_CFG_REG_SAMPLE_DIV_SHIFT);
112 
113 	writel(value, &ks_sa_rng->reg_rng->config);
114 
115 	/* Disable all interrupts from TRNG */
116 	writel(0, &ks_sa_rng->reg_rng->intmask);
117 
118 	/* Enable RNG */
119 	value = readl(&ks_sa_rng->reg_rng->control);
120 	value |= TRNG_CNTL_REG_TRNG_ENABLE;
121 	writel(value, &ks_sa_rng->reg_rng->control);
122 
123 	return 0;
124 }
125 
126 static void ks_sa_rng_cleanup(struct hwrng *rng)
127 {
128 	struct device *dev = (struct device *)rng->priv;
129 	struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);
130 
131 	/* Disable RNG */
132 	writel(0, &ks_sa_rng->reg_rng->control);
133 	regmap_write_bits(ks_sa_rng->regmap_cfg, SA_CMD_STATUS_OFS,
134 			  SA_CMD_STATUS_REG_TRNG_ENABLE, 0);
135 }
136 
137 static int ks_sa_rng_data_read(struct hwrng *rng, u32 *data)
138 {
139 	struct device *dev = (struct device *)rng->priv;
140 	struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);
141 
142 	/* Read random data */
143 	data[0] = readl(&ks_sa_rng->reg_rng->output_l);
144 	data[1] = readl(&ks_sa_rng->reg_rng->output_h);
145 
146 	writel(TRNG_INTACK_REG_READY, &ks_sa_rng->reg_rng->intack);
147 
148 	return sizeof(u32) * 2;
149 }
150 
151 static int ks_sa_rng_data_present(struct hwrng *rng, int wait)
152 {
153 	struct device *dev = (struct device *)rng->priv;
154 	struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);
155 
156 	u32	ready;
157 	int	j;
158 
159 	for (j = 0; j < SA_MAX_RNG_DATA_RETRIES; j++) {
160 		ready = readl(&ks_sa_rng->reg_rng->status);
161 		ready &= TRNG_STATUS_REG_READY;
162 
163 		if (ready || !wait)
164 			break;
165 
166 		udelay(SA_RNG_DATA_RETRY_DELAY);
167 	}
168 
169 	return ready;
170 }
171 
172 static int ks_sa_rng_probe(struct platform_device *pdev)
173 {
174 	struct ks_sa_rng	*ks_sa_rng;
175 	struct device		*dev = &pdev->dev;
176 	int			ret;
177 	struct resource		*mem;
178 
179 	ks_sa_rng = devm_kzalloc(dev, sizeof(*ks_sa_rng), GFP_KERNEL);
180 	if (!ks_sa_rng)
181 		return -ENOMEM;
182 
183 	ks_sa_rng->dev = dev;
184 	ks_sa_rng->rng = (struct hwrng) {
185 		.name = "ks_sa_hwrng",
186 		.init = ks_sa_rng_init,
187 		.data_read = ks_sa_rng_data_read,
188 		.data_present = ks_sa_rng_data_present,
189 		.cleanup = ks_sa_rng_cleanup,
190 	};
191 	ks_sa_rng->rng.priv = (unsigned long)dev;
192 
193 	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
194 	ks_sa_rng->reg_rng = devm_ioremap_resource(dev, mem);
195 	if (IS_ERR(ks_sa_rng->reg_rng))
196 		return PTR_ERR(ks_sa_rng->reg_rng);
197 
198 	ks_sa_rng->regmap_cfg =
199 		syscon_regmap_lookup_by_phandle(dev->of_node,
200 						"ti,syscon-sa-cfg");
201 
202 	if (IS_ERR(ks_sa_rng->regmap_cfg)) {
203 		dev_err(dev, "syscon_node_to_regmap failed\n");
204 		return -EINVAL;
205 	}
206 
207 	pm_runtime_enable(dev);
208 	ret = pm_runtime_get_sync(dev);
209 	if (ret < 0) {
210 		dev_err(dev, "Failed to enable SA power-domain\n");
211 		pm_runtime_disable(dev);
212 		return ret;
213 	}
214 
215 	platform_set_drvdata(pdev, ks_sa_rng);
216 
217 	return devm_hwrng_register(&pdev->dev, &ks_sa_rng->rng);
218 }
219 
220 static int ks_sa_rng_remove(struct platform_device *pdev)
221 {
222 	pm_runtime_put_sync(&pdev->dev);
223 	pm_runtime_disable(&pdev->dev);
224 
225 	return 0;
226 }
227 
228 static const struct of_device_id ks_sa_rng_dt_match[] = {
229 	{
230 		.compatible = "ti,keystone-rng",
231 	},
232 	{ },
233 };
234 MODULE_DEVICE_TABLE(of, ks_sa_rng_dt_match);
235 
236 static struct platform_driver ks_sa_rng_driver = {
237 	.driver		= {
238 		.name	= "ks-sa-rng",
239 		.of_match_table = ks_sa_rng_dt_match,
240 	},
241 	.probe		= ks_sa_rng_probe,
242 	.remove		= ks_sa_rng_remove,
243 };
244 
245 module_platform_driver(ks_sa_rng_driver);
246 
247 MODULE_DESCRIPTION("Keystone NETCP SA H/W Random Number Generator driver");
248 MODULE_AUTHOR("Vitaly Andrianov <vitalya@ti.com>");
249 MODULE_LICENSE("GPL");
250