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 	struct clk *clk;
88 };
89 
90 static void xgene_rng_expired_timer(struct timer_list *t)
91 {
92 	struct xgene_rng_dev *ctx = from_timer(ctx, t, failure_timer);
93 
94 	/* Clear failure counter as timer expired */
95 	disable_irq(ctx->irq);
96 	ctx->failure_cnt = 0;
97 	del_timer(&ctx->failure_timer);
98 	enable_irq(ctx->irq);
99 }
100 
101 static void xgene_rng_start_timer(struct xgene_rng_dev *ctx)
102 {
103 	ctx->failure_timer.expires = jiffies + 120 * HZ;
104 	add_timer(&ctx->failure_timer);
105 }
106 
107 /*
108  * Initialize or reinit free running oscillators (FROs)
109  */
110 static void xgene_rng_init_fro(struct xgene_rng_dev *ctx, u32 fro_val)
111 {
112 	writel(fro_val, ctx->csr_base + RNG_FRODETUNE);
113 	writel(0x00000000, ctx->csr_base + RNG_ALARMMASK);
114 	writel(0x00000000, ctx->csr_base + RNG_ALARMSTOP);
115 	writel(0xFFFFFFFF, ctx->csr_base + RNG_FROENABLE);
116 }
117 
118 static void xgene_rng_chk_overflow(struct xgene_rng_dev *ctx)
119 {
120 	u32 val;
121 
122 	val = readl(ctx->csr_base + RNG_INTR_STS_ACK);
123 	if (val & MONOBIT_FAIL_MASK)
124 		/*
125 		 * LFSR detected an out-of-bounds number of 1s after
126 		 * checking 20,000 bits (test T1 as specified in the
127 		 * AIS-31 standard)
128 		 */
129 		dev_err(ctx->dev, "test monobit failure error 0x%08X\n", val);
130 	if (val & POKER_FAIL_MASK)
131 		/*
132 		 * LFSR detected an out-of-bounds value in at least one
133 		 * of the 16 poker_count_X counters or an out of bounds sum
134 		 * of squares value after checking 20,000 bits (test T2 as
135 		 * specified in the AIS-31 standard)
136 		 */
137 		dev_err(ctx->dev, "test poker failure error 0x%08X\n", val);
138 	if (val & LONG_RUN_FAIL_MASK)
139 		/*
140 		 * LFSR detected a sequence of 34 identical bits
141 		 * (test T4 as specified in the AIS-31 standard)
142 		 */
143 		dev_err(ctx->dev, "test long run failure error 0x%08X\n", val);
144 	if (val & RUN_FAIL_MASK)
145 		/*
146 		 * LFSR detected an outof-bounds value for at least one
147 		 * of the running counters after checking 20,000 bits
148 		 * (test T3 as specified in the AIS-31 standard)
149 		 */
150 		dev_err(ctx->dev, "test run failure error 0x%08X\n", val);
151 	if (val & NOISE_FAIL_MASK)
152 		/* LFSR detected a sequence of 48 identical bits */
153 		dev_err(ctx->dev, "noise failure error 0x%08X\n", val);
154 	if (val & STUCK_OUT_MASK)
155 		/*
156 		 * Detected output data registers generated same value twice
157 		 * in a row
158 		 */
159 		dev_err(ctx->dev, "stuck out failure error 0x%08X\n", val);
160 
161 	if (val & SHUTDOWN_OFLO_MASK) {
162 		u32 frostopped;
163 
164 		/* FROs shut down after a second error event. Try recover. */
165 		if (++ctx->failure_cnt == 1) {
166 			/* 1st time, just recover */
167 			ctx->failure_ts = jiffies;
168 			frostopped = readl(ctx->csr_base + RNG_ALARMSTOP);
169 			xgene_rng_init_fro(ctx, frostopped);
170 
171 			/*
172 			 * We must start a timer to clear out this error
173 			 * in case the system timer wrap around
174 			 */
175 			xgene_rng_start_timer(ctx);
176 		} else {
177 			/* 2nd time failure in lesser than 1 minute? */
178 			if (time_after(ctx->failure_ts + 60 * HZ, jiffies)) {
179 				dev_err(ctx->dev,
180 					"FRO shutdown failure error 0x%08X\n",
181 					val);
182 			} else {
183 				/* 2nd time failure after 1 minutes, recover */
184 				ctx->failure_ts = jiffies;
185 				ctx->failure_cnt = 1;
186 				/*
187 				 * We must start a timer to clear out this
188 				 * error in case the system timer wrap
189 				 * around
190 				 */
191 				xgene_rng_start_timer(ctx);
192 			}
193 			frostopped = readl(ctx->csr_base + RNG_ALARMSTOP);
194 			xgene_rng_init_fro(ctx, frostopped);
195 		}
196 	}
197 	/* Clear them all */
198 	writel(val, ctx->csr_base + RNG_INTR_STS_ACK);
199 }
200 
201 static irqreturn_t xgene_rng_irq_handler(int irq, void *id)
202 {
203 	struct xgene_rng_dev *ctx = (struct xgene_rng_dev *) id;
204 
205 	/* RNG Alarm Counter overflow */
206 	xgene_rng_chk_overflow(ctx);
207 
208 	return IRQ_HANDLED;
209 }
210 
211 static int xgene_rng_data_present(struct hwrng *rng, int wait)
212 {
213 	struct xgene_rng_dev *ctx = (struct xgene_rng_dev *) rng->priv;
214 	u32 i, val = 0;
215 
216 	for (i = 0; i < XGENE_RNG_RETRY_COUNT; i++) {
217 		val = readl(ctx->csr_base + RNG_INTR_STS_ACK);
218 		if ((val & READY_MASK) || !wait)
219 			break;
220 		udelay(XGENE_RNG_RETRY_INTERVAL);
221 	}
222 
223 	return (val & READY_MASK);
224 }
225 
226 static int xgene_rng_data_read(struct hwrng *rng, u32 *data)
227 {
228 	struct xgene_rng_dev *ctx = (struct xgene_rng_dev *) rng->priv;
229 	int i;
230 
231 	for (i = 0; i < ctx->datum_size; i++)
232 		data[i] = readl(ctx->csr_base + RNG_INOUT_0 + i * 4);
233 
234 	/* Clear ready bit to start next transaction */
235 	writel(READY_MASK, ctx->csr_base + RNG_INTR_STS_ACK);
236 
237 	return ctx->datum_size << 2;
238 }
239 
240 static void xgene_rng_init_internal(struct xgene_rng_dev *ctx)
241 {
242 	u32 val;
243 
244 	writel(0x00000000, ctx->csr_base + RNG_CONTROL);
245 
246 	val = MAX_REFILL_CYCLES_SET(0, 10);
247 	val = MIN_REFILL_CYCLES_SET(val, 10);
248 	writel(val, ctx->csr_base + RNG_CONFIG);
249 
250 	val = ALARM_THRESHOLD_SET(0, 0xFF);
251 	writel(val, ctx->csr_base + RNG_ALARMCNT);
252 
253 	xgene_rng_init_fro(ctx, 0);
254 
255 	writel(MONOBIT_FAIL_MASK |
256 		POKER_FAIL_MASK	|
257 		LONG_RUN_FAIL_MASK |
258 		RUN_FAIL_MASK |
259 		NOISE_FAIL_MASK |
260 		STUCK_OUT_MASK |
261 		SHUTDOWN_OFLO_MASK |
262 		READY_MASK, ctx->csr_base + RNG_INTR_STS_ACK);
263 
264 	val = ENABLE_RNG_SET(0, 1);
265 	val = MONOBIT_FAIL_MASK_SET(val, 1);
266 	val = POKER_FAIL_MASK_SET(val, 1);
267 	val = LONG_RUN_FAIL_MASK_SET(val, 1);
268 	val = RUN_FAIL_MASK_SET(val, 1);
269 	val = NOISE_FAIL_MASK_SET(val, 1);
270 	val = STUCK_OUT_MASK_SET(val, 1);
271 	val = SHUTDOWN_OFLO_MASK_SET(val, 1);
272 	writel(val, ctx->csr_base + RNG_CONTROL);
273 }
274 
275 static int xgene_rng_init(struct hwrng *rng)
276 {
277 	struct xgene_rng_dev *ctx = (struct xgene_rng_dev *) rng->priv;
278 
279 	ctx->failure_cnt = 0;
280 	timer_setup(&ctx->failure_timer, xgene_rng_expired_timer, 0);
281 
282 	ctx->revision = readl(ctx->csr_base + RNG_EIP_REV);
283 
284 	dev_dbg(ctx->dev, "Rev %d.%d.%d\n",
285 		MAJOR_HW_REV_RD(ctx->revision),
286 		MINOR_HW_REV_RD(ctx->revision),
287 		HW_PATCH_LEVEL_RD(ctx->revision));
288 
289 	dev_dbg(ctx->dev, "Options 0x%08X",
290 		readl(ctx->csr_base + RNG_OPTIONS));
291 
292 	xgene_rng_init_internal(ctx);
293 
294 	ctx->datum_size = RNG_MAX_DATUM;
295 
296 	return 0;
297 }
298 
299 #ifdef CONFIG_ACPI
300 static const struct acpi_device_id xgene_rng_acpi_match[] = {
301 	{ "APMC0D18", },
302 	{ }
303 };
304 MODULE_DEVICE_TABLE(acpi, xgene_rng_acpi_match);
305 #endif
306 
307 static struct hwrng xgene_rng_func = {
308 	.name		= "xgene-rng",
309 	.init		= xgene_rng_init,
310 	.data_present	= xgene_rng_data_present,
311 	.data_read	= xgene_rng_data_read,
312 };
313 
314 static int xgene_rng_probe(struct platform_device *pdev)
315 {
316 	struct xgene_rng_dev *ctx;
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 		dev_err(&pdev->dev, "Could not request RNG alarm IRQ\n");
342 		return rc;
343 	}
344 
345 	/* Enable IP clock */
346 	ctx->clk = devm_clk_get(&pdev->dev, NULL);
347 	if (IS_ERR(ctx->clk)) {
348 		dev_warn(&pdev->dev, "Couldn't get the clock for RNG\n");
349 	} else {
350 		rc = clk_prepare_enable(ctx->clk);
351 		if (rc) {
352 			dev_warn(&pdev->dev,
353 				 "clock prepare enable failed for RNG");
354 			return rc;
355 		}
356 	}
357 
358 	xgene_rng_func.priv = (unsigned long) ctx;
359 
360 	rc = devm_hwrng_register(&pdev->dev, &xgene_rng_func);
361 	if (rc) {
362 		dev_err(&pdev->dev, "RNG registering failed error %d\n", rc);
363 		if (!IS_ERR(ctx->clk))
364 			clk_disable_unprepare(ctx->clk);
365 		return rc;
366 	}
367 
368 	rc = device_init_wakeup(&pdev->dev, 1);
369 	if (rc) {
370 		dev_err(&pdev->dev, "RNG device_init_wakeup failed error %d\n",
371 			rc);
372 		if (!IS_ERR(ctx->clk))
373 			clk_disable_unprepare(ctx->clk);
374 		return rc;
375 	}
376 
377 	return 0;
378 }
379 
380 static int xgene_rng_remove(struct platform_device *pdev)
381 {
382 	struct xgene_rng_dev *ctx = platform_get_drvdata(pdev);
383 	int rc;
384 
385 	rc = device_init_wakeup(&pdev->dev, 0);
386 	if (rc)
387 		dev_err(&pdev->dev, "RNG init wakeup failed error %d\n", rc);
388 	if (!IS_ERR(ctx->clk))
389 		clk_disable_unprepare(ctx->clk);
390 
391 	return rc;
392 }
393 
394 static const struct of_device_id xgene_rng_of_match[] = {
395 	{ .compatible = "apm,xgene-rng" },
396 	{ }
397 };
398 
399 MODULE_DEVICE_TABLE(of, xgene_rng_of_match);
400 
401 static struct platform_driver xgene_rng_driver = {
402 	.probe = xgene_rng_probe,
403 	.remove	= xgene_rng_remove,
404 	.driver = {
405 		.name		= "xgene-rng",
406 		.of_match_table = xgene_rng_of_match,
407 		.acpi_match_table = ACPI_PTR(xgene_rng_acpi_match),
408 	},
409 };
410 
411 module_platform_driver(xgene_rng_driver);
412 MODULE_DESCRIPTION("APM X-Gene RNG driver");
413 MODULE_LICENSE("GPL");
414