1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * APM X-Gene SoC RNG Driver
4  *
5  * Copyright (c) 2014, Applied Micro Circuits Corporation
6  * Author: Rameshwar Prasad Sahu <rsahu@apm.com>
7  *	   Shamal Winchurkar <swinchurkar@apm.com>
8  *	   Feng Kan <fkan@apm.com>
9  */
10 
11 #include <linux/acpi.h>
12 #include <linux/clk.h>
13 #include <linux/delay.h>
14 #include <linux/hw_random.h>
15 #include <linux/init.h>
16 #include <linux/interrupt.h>
17 #include <linux/module.h>
18 #include <linux/of_platform.h>
19 #include <linux/of_irq.h>
20 #include <linux/of_address.h>
21 #include <linux/timer.h>
22 
23 #define RNG_MAX_DATUM			4
24 #define MAX_TRY				100
25 #define XGENE_RNG_RETRY_COUNT		20
26 #define XGENE_RNG_RETRY_INTERVAL	10
27 
28 /* RNG  Registers */
29 #define RNG_INOUT_0			0x00
30 #define RNG_INTR_STS_ACK		0x10
31 #define RNG_CONTROL			0x14
32 #define RNG_CONFIG			0x18
33 #define RNG_ALARMCNT			0x1c
34 #define RNG_FROENABLE			0x20
35 #define RNG_FRODETUNE			0x24
36 #define RNG_ALARMMASK			0x28
37 #define RNG_ALARMSTOP			0x2c
38 #define RNG_OPTIONS			0x78
39 #define RNG_EIP_REV			0x7c
40 
41 #define MONOBIT_FAIL_MASK		BIT(7)
42 #define POKER_FAIL_MASK			BIT(6)
43 #define LONG_RUN_FAIL_MASK		BIT(5)
44 #define RUN_FAIL_MASK			BIT(4)
45 #define NOISE_FAIL_MASK			BIT(3)
46 #define STUCK_OUT_MASK			BIT(2)
47 #define SHUTDOWN_OFLO_MASK		BIT(1)
48 #define READY_MASK			BIT(0)
49 
50 #define MAJOR_HW_REV_RD(src)		(((src) & 0x0f000000) >> 24)
51 #define MINOR_HW_REV_RD(src)		(((src) & 0x00f00000) >> 20)
52 #define HW_PATCH_LEVEL_RD(src)		(((src) & 0x000f0000) >> 16)
53 #define MAX_REFILL_CYCLES_SET(dst, src) \
54 			((dst & ~0xffff0000) | (((u32)src << 16) & 0xffff0000))
55 #define MIN_REFILL_CYCLES_SET(dst, src) \
56 			((dst & ~0x000000ff) | (((u32)src) & 0x000000ff))
57 #define ALARM_THRESHOLD_SET(dst, src) \
58 			((dst & ~0x000000ff) | (((u32)src) & 0x000000ff))
59 #define ENABLE_RNG_SET(dst, src) \
60 			((dst & ~BIT(10)) | (((u32)src << 10) & BIT(10)))
61 #define REGSPEC_TEST_MODE_SET(dst, src) \
62 			((dst & ~BIT(8)) | (((u32)src << 8) & BIT(8)))
63 #define MONOBIT_FAIL_MASK_SET(dst, src) \
64 			((dst & ~BIT(7)) | (((u32)src << 7) & BIT(7)))
65 #define POKER_FAIL_MASK_SET(dst, src) \
66 			((dst & ~BIT(6)) | (((u32)src << 6) & BIT(6)))
67 #define LONG_RUN_FAIL_MASK_SET(dst, src) \
68 			((dst & ~BIT(5)) | (((u32)src << 5) & BIT(5)))
69 #define RUN_FAIL_MASK_SET(dst, src) \
70 			((dst & ~BIT(4)) | (((u32)src << 4) & BIT(4)))
71 #define NOISE_FAIL_MASK_SET(dst, src) \
72 			((dst & ~BIT(3)) | (((u32)src << 3) & BIT(3)))
73 #define STUCK_OUT_MASK_SET(dst, src) \
74 			((dst & ~BIT(2)) | (((u32)src << 2) & BIT(2)))
75 #define SHUTDOWN_OFLO_MASK_SET(dst, src) \
76 			((dst & ~BIT(1)) | (((u32)src << 1) & BIT(1)))
77 
78 struct xgene_rng_dev {
79 	u32 irq;
80 	void  __iomem *csr_base;
81 	u32 revision;
82 	u32 datum_size;
83 	u32 failure_cnt;	/* Failure count last minute */
84 	unsigned long failure_ts;/* First failure timestamp */
85 	struct timer_list failure_timer;
86 	struct device *dev;
87 };
88 
89 static void xgene_rng_expired_timer(struct timer_list *t)
90 {
91 	struct xgene_rng_dev *ctx = from_timer(ctx, t, failure_timer);
92 
93 	/* Clear failure counter as timer expired */
94 	disable_irq(ctx->irq);
95 	ctx->failure_cnt = 0;
96 	del_timer(&ctx->failure_timer);
97 	enable_irq(ctx->irq);
98 }
99 
100 static void xgene_rng_start_timer(struct xgene_rng_dev *ctx)
101 {
102 	ctx->failure_timer.expires = jiffies + 120 * HZ;
103 	add_timer(&ctx->failure_timer);
104 }
105 
106 /*
107  * Initialize or reinit free running oscillators (FROs)
108  */
109 static void xgene_rng_init_fro(struct xgene_rng_dev *ctx, u32 fro_val)
110 {
111 	writel(fro_val, ctx->csr_base + RNG_FRODETUNE);
112 	writel(0x00000000, ctx->csr_base + RNG_ALARMMASK);
113 	writel(0x00000000, ctx->csr_base + RNG_ALARMSTOP);
114 	writel(0xFFFFFFFF, ctx->csr_base + RNG_FROENABLE);
115 }
116 
117 static void xgene_rng_chk_overflow(struct xgene_rng_dev *ctx)
118 {
119 	u32 val;
120 
121 	val = readl(ctx->csr_base + RNG_INTR_STS_ACK);
122 	if (val & MONOBIT_FAIL_MASK)
123 		/*
124 		 * LFSR detected an out-of-bounds number of 1s after
125 		 * checking 20,000 bits (test T1 as specified in the
126 		 * AIS-31 standard)
127 		 */
128 		dev_err(ctx->dev, "test monobit failure error 0x%08X\n", val);
129 	if (val & POKER_FAIL_MASK)
130 		/*
131 		 * LFSR detected an out-of-bounds value in at least one
132 		 * of the 16 poker_count_X counters or an out of bounds sum
133 		 * of squares value after checking 20,000 bits (test T2 as
134 		 * specified in the AIS-31 standard)
135 		 */
136 		dev_err(ctx->dev, "test poker failure error 0x%08X\n", val);
137 	if (val & LONG_RUN_FAIL_MASK)
138 		/*
139 		 * LFSR detected a sequence of 34 identical bits
140 		 * (test T4 as specified in the AIS-31 standard)
141 		 */
142 		dev_err(ctx->dev, "test long run failure error 0x%08X\n", val);
143 	if (val & RUN_FAIL_MASK)
144 		/*
145 		 * LFSR detected an outof-bounds value for at least one
146 		 * of the running counters after checking 20,000 bits
147 		 * (test T3 as specified in the AIS-31 standard)
148 		 */
149 		dev_err(ctx->dev, "test run failure error 0x%08X\n", val);
150 	if (val & NOISE_FAIL_MASK)
151 		/* LFSR detected a sequence of 48 identical bits */
152 		dev_err(ctx->dev, "noise failure error 0x%08X\n", val);
153 	if (val & STUCK_OUT_MASK)
154 		/*
155 		 * Detected output data registers generated same value twice
156 		 * in a row
157 		 */
158 		dev_err(ctx->dev, "stuck out failure error 0x%08X\n", val);
159 
160 	if (val & SHUTDOWN_OFLO_MASK) {
161 		u32 frostopped;
162 
163 		/* FROs shut down after a second error event. Try recover. */
164 		if (++ctx->failure_cnt == 1) {
165 			/* 1st time, just recover */
166 			ctx->failure_ts = jiffies;
167 			frostopped = readl(ctx->csr_base + RNG_ALARMSTOP);
168 			xgene_rng_init_fro(ctx, frostopped);
169 
170 			/*
171 			 * We must start a timer to clear out this error
172 			 * in case the system timer wrap around
173 			 */
174 			xgene_rng_start_timer(ctx);
175 		} else {
176 			/* 2nd time failure in lesser than 1 minute? */
177 			if (time_after(ctx->failure_ts + 60 * HZ, jiffies)) {
178 				dev_err(ctx->dev,
179 					"FRO shutdown failure error 0x%08X\n",
180 					val);
181 			} else {
182 				/* 2nd time failure after 1 minutes, recover */
183 				ctx->failure_ts = jiffies;
184 				ctx->failure_cnt = 1;
185 				/*
186 				 * We must start a timer to clear out this
187 				 * error in case the system timer wrap
188 				 * around
189 				 */
190 				xgene_rng_start_timer(ctx);
191 			}
192 			frostopped = readl(ctx->csr_base + RNG_ALARMSTOP);
193 			xgene_rng_init_fro(ctx, frostopped);
194 		}
195 	}
196 	/* Clear them all */
197 	writel(val, ctx->csr_base + RNG_INTR_STS_ACK);
198 }
199 
200 static irqreturn_t xgene_rng_irq_handler(int irq, void *id)
201 {
202 	struct xgene_rng_dev *ctx = id;
203 
204 	/* RNG Alarm Counter overflow */
205 	xgene_rng_chk_overflow(ctx);
206 
207 	return IRQ_HANDLED;
208 }
209 
210 static int xgene_rng_data_present(struct hwrng *rng, int wait)
211 {
212 	struct xgene_rng_dev *ctx = (struct xgene_rng_dev *) rng->priv;
213 	u32 i, val = 0;
214 
215 	for (i = 0; i < XGENE_RNG_RETRY_COUNT; i++) {
216 		val = readl(ctx->csr_base + RNG_INTR_STS_ACK);
217 		if ((val & READY_MASK) || !wait)
218 			break;
219 		udelay(XGENE_RNG_RETRY_INTERVAL);
220 	}
221 
222 	return (val & READY_MASK);
223 }
224 
225 static int xgene_rng_data_read(struct hwrng *rng, u32 *data)
226 {
227 	struct xgene_rng_dev *ctx = (struct xgene_rng_dev *) rng->priv;
228 	int i;
229 
230 	for (i = 0; i < ctx->datum_size; i++)
231 		data[i] = readl(ctx->csr_base + RNG_INOUT_0 + i * 4);
232 
233 	/* Clear ready bit to start next transaction */
234 	writel(READY_MASK, ctx->csr_base + RNG_INTR_STS_ACK);
235 
236 	return ctx->datum_size << 2;
237 }
238 
239 static void xgene_rng_init_internal(struct xgene_rng_dev *ctx)
240 {
241 	u32 val;
242 
243 	writel(0x00000000, ctx->csr_base + RNG_CONTROL);
244 
245 	val = MAX_REFILL_CYCLES_SET(0, 10);
246 	val = MIN_REFILL_CYCLES_SET(val, 10);
247 	writel(val, ctx->csr_base + RNG_CONFIG);
248 
249 	val = ALARM_THRESHOLD_SET(0, 0xFF);
250 	writel(val, ctx->csr_base + RNG_ALARMCNT);
251 
252 	xgene_rng_init_fro(ctx, 0);
253 
254 	writel(MONOBIT_FAIL_MASK |
255 		POKER_FAIL_MASK	|
256 		LONG_RUN_FAIL_MASK |
257 		RUN_FAIL_MASK |
258 		NOISE_FAIL_MASK |
259 		STUCK_OUT_MASK |
260 		SHUTDOWN_OFLO_MASK |
261 		READY_MASK, ctx->csr_base + RNG_INTR_STS_ACK);
262 
263 	val = ENABLE_RNG_SET(0, 1);
264 	val = MONOBIT_FAIL_MASK_SET(val, 1);
265 	val = POKER_FAIL_MASK_SET(val, 1);
266 	val = LONG_RUN_FAIL_MASK_SET(val, 1);
267 	val = RUN_FAIL_MASK_SET(val, 1);
268 	val = NOISE_FAIL_MASK_SET(val, 1);
269 	val = STUCK_OUT_MASK_SET(val, 1);
270 	val = SHUTDOWN_OFLO_MASK_SET(val, 1);
271 	writel(val, ctx->csr_base + RNG_CONTROL);
272 }
273 
274 static int xgene_rng_init(struct hwrng *rng)
275 {
276 	struct xgene_rng_dev *ctx = (struct xgene_rng_dev *) rng->priv;
277 
278 	ctx->failure_cnt = 0;
279 	timer_setup(&ctx->failure_timer, xgene_rng_expired_timer, 0);
280 
281 	ctx->revision = readl(ctx->csr_base + RNG_EIP_REV);
282 
283 	dev_dbg(ctx->dev, "Rev %d.%d.%d\n",
284 		MAJOR_HW_REV_RD(ctx->revision),
285 		MINOR_HW_REV_RD(ctx->revision),
286 		HW_PATCH_LEVEL_RD(ctx->revision));
287 
288 	dev_dbg(ctx->dev, "Options 0x%08X",
289 		readl(ctx->csr_base + RNG_OPTIONS));
290 
291 	xgene_rng_init_internal(ctx);
292 
293 	ctx->datum_size = RNG_MAX_DATUM;
294 
295 	return 0;
296 }
297 
298 #ifdef CONFIG_ACPI
299 static const struct acpi_device_id xgene_rng_acpi_match[] = {
300 	{ "APMC0D18", },
301 	{ }
302 };
303 MODULE_DEVICE_TABLE(acpi, xgene_rng_acpi_match);
304 #endif
305 
306 static struct hwrng xgene_rng_func = {
307 	.name		= "xgene-rng",
308 	.init		= xgene_rng_init,
309 	.data_present	= xgene_rng_data_present,
310 	.data_read	= xgene_rng_data_read,
311 };
312 
313 static int xgene_rng_probe(struct platform_device *pdev)
314 {
315 	struct xgene_rng_dev *ctx;
316 	struct clk *clk;
317 	int rc = 0;
318 
319 	ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx), GFP_KERNEL);
320 	if (!ctx)
321 		return -ENOMEM;
322 
323 	ctx->dev = &pdev->dev;
324 	platform_set_drvdata(pdev, ctx);
325 
326 	ctx->csr_base = devm_platform_ioremap_resource(pdev, 0);
327 	if (IS_ERR(ctx->csr_base))
328 		return PTR_ERR(ctx->csr_base);
329 
330 	rc = platform_get_irq(pdev, 0);
331 	if (rc < 0)
332 		return rc;
333 	ctx->irq = rc;
334 
335 	dev_dbg(&pdev->dev, "APM X-Gene RNG BASE %p ALARM IRQ %d",
336 		ctx->csr_base, ctx->irq);
337 
338 	rc = devm_request_irq(&pdev->dev, ctx->irq, xgene_rng_irq_handler, 0,
339 				dev_name(&pdev->dev), ctx);
340 	if (rc)
341 		return dev_err_probe(&pdev->dev, rc, "Could not request RNG alarm IRQ\n");
342 
343 	/* Enable IP clock */
344 	clk = devm_clk_get_optional_enabled(&pdev->dev, NULL);
345 	if (IS_ERR(clk))
346 		return dev_err_probe(&pdev->dev, PTR_ERR(clk), "Couldn't get the clock for RNG\n");
347 
348 	xgene_rng_func.priv = (unsigned long) ctx;
349 
350 	rc = devm_hwrng_register(&pdev->dev, &xgene_rng_func);
351 	if (rc)
352 		return dev_err_probe(&pdev->dev, rc, "RNG registering failed\n");
353 
354 	rc = device_init_wakeup(&pdev->dev, 1);
355 	if (rc)
356 		return dev_err_probe(&pdev->dev, rc, "RNG device_init_wakeup failed\n");
357 
358 	return 0;
359 }
360 
361 static int xgene_rng_remove(struct platform_device *pdev)
362 {
363 	int rc;
364 
365 	rc = device_init_wakeup(&pdev->dev, 0);
366 	if (rc)
367 		dev_err(&pdev->dev, "RNG init wakeup failed error %d\n", rc);
368 
369 	return 0;
370 }
371 
372 static const struct of_device_id xgene_rng_of_match[] = {
373 	{ .compatible = "apm,xgene-rng" },
374 	{ }
375 };
376 
377 MODULE_DEVICE_TABLE(of, xgene_rng_of_match);
378 
379 static struct platform_driver xgene_rng_driver = {
380 	.probe = xgene_rng_probe,
381 	.remove	= xgene_rng_remove,
382 	.driver = {
383 		.name		= "xgene-rng",
384 		.of_match_table = xgene_rng_of_match,
385 		.acpi_match_table = ACPI_PTR(xgene_rng_acpi_match),
386 	},
387 };
388 
389 module_platform_driver(xgene_rng_driver);
390 MODULE_DESCRIPTION("APM X-Gene RNG driver");
391 MODULE_LICENSE("GPL");
392