1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (C) 2016 Google, Inc
4  *
5  * This device driver implements a TCG PTP FIFO interface over SPI for chips
6  * with Cr50 firmware.
7  * It is based on tpm_tis_spi driver by Peter Huewe and Christophe Ricard.
8  */
9 
10 #include <linux/completion.h>
11 #include <linux/interrupt.h>
12 #include <linux/module.h>
13 #include <linux/of.h>
14 #include <linux/pm.h>
15 #include <linux/spi/spi.h>
16 #include <linux/wait.h>
17 
18 #include "tpm_tis_core.h"
19 #include "tpm_tis_spi.h"
20 
21 /*
22  * Cr50 timing constants:
23  * - can go to sleep not earlier than after CR50_SLEEP_DELAY_MSEC.
24  * - needs up to CR50_WAKE_START_DELAY_USEC to wake after sleep.
25  * - requires waiting for "ready" IRQ, if supported; or waiting for at least
26  *   CR50_NOIRQ_ACCESS_DELAY_MSEC between transactions, if IRQ is not supported.
27  * - waits for up to CR50_FLOW_CONTROL for flow control 'ready' indication.
28  */
29 #define CR50_SLEEP_DELAY_MSEC			1000
30 #define CR50_WAKE_START_DELAY_USEC		1000
31 #define CR50_NOIRQ_ACCESS_DELAY			msecs_to_jiffies(2)
32 #define CR50_READY_IRQ_TIMEOUT			msecs_to_jiffies(TPM2_TIMEOUT_A)
33 #define CR50_FLOW_CONTROL			msecs_to_jiffies(TPM2_TIMEOUT_A)
34 #define MAX_IRQ_CONFIRMATION_ATTEMPTS		3
35 
36 #define TPM_CR50_FW_VER(l)			(0x0f90 | ((l) << 12))
37 #define TPM_CR50_MAX_FW_VER_LEN			64
38 
39 struct cr50_spi_phy {
40 	struct tpm_tis_spi_phy spi_phy;
41 
42 	struct mutex time_track_mutex;
43 	unsigned long last_access;
44 
45 	unsigned long access_delay;
46 
47 	unsigned int irq_confirmation_attempt;
48 	bool irq_needs_confirmation;
49 	bool irq_confirmed;
50 };
51 
52 static inline struct cr50_spi_phy *to_cr50_spi_phy(struct tpm_tis_spi_phy *phy)
53 {
54 	return container_of(phy, struct cr50_spi_phy, spi_phy);
55 }
56 
57 /*
58  * The cr50 interrupt handler just signals waiting threads that the
59  * interrupt was asserted.  It does not do any processing triggered
60  * by interrupts but is instead used to avoid fixed delays.
61  */
62 static irqreturn_t cr50_spi_irq_handler(int dummy, void *dev_id)
63 {
64 	struct cr50_spi_phy *cr50_phy = dev_id;
65 
66 	cr50_phy->irq_confirmed = true;
67 	complete(&cr50_phy->spi_phy.ready);
68 
69 	return IRQ_HANDLED;
70 }
71 
72 /*
73  * Cr50 needs to have at least some delay between consecutive
74  * transactions. Make sure we wait.
75  */
76 static void cr50_ensure_access_delay(struct cr50_spi_phy *phy)
77 {
78 	unsigned long allowed_access = phy->last_access + phy->access_delay;
79 	unsigned long time_now = jiffies;
80 	struct device *dev = &phy->spi_phy.spi_device->dev;
81 
82 	/*
83 	 * Note: There is a small chance, if Cr50 is not accessed in a few days,
84 	 * that time_in_range will not provide the correct result after the wrap
85 	 * around for jiffies. In this case, we'll have an unneeded short delay,
86 	 * which is fine.
87 	 */
88 	if (time_in_range_open(time_now, phy->last_access, allowed_access)) {
89 		unsigned long remaining, timeout = allowed_access - time_now;
90 
91 		remaining = wait_for_completion_timeout(&phy->spi_phy.ready,
92 							timeout);
93 		if (!remaining && phy->irq_confirmed)
94 			dev_warn(dev, "Timeout waiting for TPM ready IRQ\n");
95 	}
96 
97 	if (phy->irq_needs_confirmation) {
98 		unsigned int attempt = ++phy->irq_confirmation_attempt;
99 
100 		if (phy->irq_confirmed) {
101 			phy->irq_needs_confirmation = false;
102 			phy->access_delay = CR50_READY_IRQ_TIMEOUT;
103 			dev_info(dev, "TPM ready IRQ confirmed on attempt %u\n",
104 				 attempt);
105 		} else if (attempt > MAX_IRQ_CONFIRMATION_ATTEMPTS) {
106 			phy->irq_needs_confirmation = false;
107 			dev_warn(dev, "IRQ not confirmed - will use delays\n");
108 		}
109 	}
110 }
111 
112 /*
113  * Cr50 might go to sleep if there is no SPI activity for some time and
114  * miss the first few bits/bytes on the bus. In such case, wake it up
115  * by asserting CS and give it time to start up.
116  */
117 static bool cr50_needs_waking(struct cr50_spi_phy *phy)
118 {
119 	/*
120 	 * Note: There is a small chance, if Cr50 is not accessed in a few days,
121 	 * that time_in_range will not provide the correct result after the wrap
122 	 * around for jiffies. In this case, we'll probably timeout or read
123 	 * incorrect value from TPM_STS and just retry the operation.
124 	 */
125 	return !time_in_range_open(jiffies, phy->last_access,
126 				   phy->spi_phy.wake_after);
127 }
128 
129 static void cr50_wake_if_needed(struct cr50_spi_phy *cr50_phy)
130 {
131 	struct tpm_tis_spi_phy *phy = &cr50_phy->spi_phy;
132 
133 	if (cr50_needs_waking(cr50_phy)) {
134 		/* Assert CS, wait 1 msec, deassert CS */
135 		struct spi_transfer spi_cs_wake = {
136 			.delay = {
137 				.value = 1000,
138 				.unit = SPI_DELAY_UNIT_USECS
139 			}
140 		};
141 
142 		spi_sync_transfer(phy->spi_device, &spi_cs_wake, 1);
143 		/* Wait for it to fully wake */
144 		usleep_range(CR50_WAKE_START_DELAY_USEC,
145 			     CR50_WAKE_START_DELAY_USEC * 2);
146 	}
147 
148 	/* Reset the time when we need to wake Cr50 again */
149 	phy->wake_after = jiffies + msecs_to_jiffies(CR50_SLEEP_DELAY_MSEC);
150 }
151 
152 /*
153  * Flow control: clock the bus and wait for cr50 to set LSB before
154  * sending/receiving data. TCG PTP spec allows it to happen during
155  * the last byte of header, but cr50 never does that in practice,
156  * and earlier versions had a bug when it was set too early, so don't
157  * check for it during header transfer.
158  */
159 static int cr50_spi_flow_control(struct tpm_tis_spi_phy *phy,
160 				 struct spi_transfer *spi_xfer)
161 {
162 	struct device *dev = &phy->spi_device->dev;
163 	unsigned long timeout = jiffies + CR50_FLOW_CONTROL;
164 	struct spi_message m;
165 	int ret;
166 
167 	spi_xfer->len = 1;
168 
169 	do {
170 		spi_message_init(&m);
171 		spi_message_add_tail(spi_xfer, &m);
172 		ret = spi_sync_locked(phy->spi_device, &m);
173 		if (ret < 0)
174 			return ret;
175 
176 		if (time_after(jiffies, timeout)) {
177 			dev_warn(dev, "Timeout during flow control\n");
178 			return -EBUSY;
179 		}
180 	} while (!(phy->iobuf[0] & 0x01));
181 
182 	return 0;
183 }
184 
185 static int tpm_tis_spi_cr50_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
186 				     u8 *in, const u8 *out)
187 {
188 	struct tpm_tis_spi_phy *phy = to_tpm_tis_spi_phy(data);
189 	struct cr50_spi_phy *cr50_phy = to_cr50_spi_phy(phy);
190 	int ret;
191 
192 	mutex_lock(&cr50_phy->time_track_mutex);
193 	/*
194 	 * Do this outside of spi_bus_lock in case cr50 is not the
195 	 * only device on that spi bus.
196 	 */
197 	cr50_ensure_access_delay(cr50_phy);
198 	cr50_wake_if_needed(cr50_phy);
199 
200 	ret = tpm_tis_spi_transfer(data, addr, len, in, out);
201 
202 	cr50_phy->last_access = jiffies;
203 	mutex_unlock(&cr50_phy->time_track_mutex);
204 
205 	return ret;
206 }
207 
208 static int tpm_tis_spi_cr50_read_bytes(struct tpm_tis_data *data, u32 addr,
209 				       u16 len, u8 *result)
210 {
211 	return tpm_tis_spi_cr50_transfer(data, addr, len, result, NULL);
212 }
213 
214 static int tpm_tis_spi_cr50_write_bytes(struct tpm_tis_data *data, u32 addr,
215 					u16 len, const u8 *value)
216 {
217 	return tpm_tis_spi_cr50_transfer(data, addr, len, NULL, value);
218 }
219 
220 static const struct tpm_tis_phy_ops tpm_spi_cr50_phy_ops = {
221 	.read_bytes = tpm_tis_spi_cr50_read_bytes,
222 	.write_bytes = tpm_tis_spi_cr50_write_bytes,
223 	.read16 = tpm_tis_spi_read16,
224 	.read32 = tpm_tis_spi_read32,
225 	.write32 = tpm_tis_spi_write32,
226 };
227 
228 static void cr50_print_fw_version(struct tpm_tis_data *data)
229 {
230 	struct tpm_tis_spi_phy *phy = to_tpm_tis_spi_phy(data);
231 	int i, len = 0;
232 	char fw_ver[TPM_CR50_MAX_FW_VER_LEN + 1];
233 	char fw_ver_block[4];
234 
235 	/*
236 	 * Write anything to TPM_CR50_FW_VER to start from the beginning
237 	 * of the version string
238 	 */
239 	tpm_tis_write8(data, TPM_CR50_FW_VER(data->locality), 0);
240 
241 	/* Read the string, 4 bytes at a time, until we get '\0' */
242 	do {
243 		tpm_tis_read_bytes(data, TPM_CR50_FW_VER(data->locality), 4,
244 				   fw_ver_block);
245 		for (i = 0; i < 4 && fw_ver_block[i]; ++len, ++i)
246 			fw_ver[len] = fw_ver_block[i];
247 	} while (i == 4 && len < TPM_CR50_MAX_FW_VER_LEN);
248 	fw_ver[len] = '\0';
249 
250 	dev_info(&phy->spi_device->dev, "Cr50 firmware version: %s\n", fw_ver);
251 }
252 
253 int cr50_spi_probe(struct spi_device *spi)
254 {
255 	struct tpm_tis_spi_phy *phy;
256 	struct cr50_spi_phy *cr50_phy;
257 	int ret;
258 	struct tpm_chip *chip;
259 
260 	cr50_phy = devm_kzalloc(&spi->dev, sizeof(*cr50_phy), GFP_KERNEL);
261 	if (!cr50_phy)
262 		return -ENOMEM;
263 
264 	phy = &cr50_phy->spi_phy;
265 	phy->flow_control = cr50_spi_flow_control;
266 	phy->wake_after = jiffies;
267 	init_completion(&phy->ready);
268 
269 	cr50_phy->access_delay = CR50_NOIRQ_ACCESS_DELAY;
270 	cr50_phy->last_access = jiffies;
271 	mutex_init(&cr50_phy->time_track_mutex);
272 
273 	if (spi->irq > 0) {
274 		ret = devm_request_irq(&spi->dev, spi->irq,
275 				       cr50_spi_irq_handler,
276 				       IRQF_TRIGGER_RISING | IRQF_ONESHOT,
277 				       "cr50_spi", cr50_phy);
278 		if (ret < 0) {
279 			if (ret == -EPROBE_DEFER)
280 				return ret;
281 			dev_warn(&spi->dev, "Requesting IRQ %d failed: %d\n",
282 				 spi->irq, ret);
283 			/*
284 			 * This is not fatal, the driver will fall back to
285 			 * delays automatically, since ready will never
286 			 * be completed without a registered irq handler.
287 			 * So, just fall through.
288 			 */
289 		} else {
290 			/*
291 			 * IRQ requested, let's verify that it is actually
292 			 * triggered, before relying on it.
293 			 */
294 			cr50_phy->irq_needs_confirmation = true;
295 		}
296 	} else {
297 		dev_warn(&spi->dev,
298 			 "No IRQ - will use delays between transactions.\n");
299 	}
300 
301 	ret = tpm_tis_spi_init(spi, phy, -1, &tpm_spi_cr50_phy_ops);
302 	if (ret)
303 		return ret;
304 
305 	cr50_print_fw_version(&phy->priv);
306 
307 	chip = dev_get_drvdata(&spi->dev);
308 	chip->flags |= TPM_CHIP_FLAG_FIRMWARE_POWER_MANAGED;
309 
310 	return 0;
311 }
312 
313 #ifdef CONFIG_PM_SLEEP
314 int tpm_tis_spi_resume(struct device *dev)
315 {
316 	struct tpm_chip *chip = dev_get_drvdata(dev);
317 	struct tpm_tis_data *data = dev_get_drvdata(&chip->dev);
318 	struct tpm_tis_spi_phy *phy = to_tpm_tis_spi_phy(data);
319 	/*
320 	 * Jiffies not increased during suspend, so we need to reset
321 	 * the time to wake Cr50 after resume.
322 	 */
323 	phy->wake_after = jiffies;
324 
325 	return tpm_tis_resume(dev);
326 }
327 #endif
328