1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Copyright (C) 2015 Masahiro Yamada <yamada.masahiro@socionext.com>
4  */
5 
6 #include <linux/clk.h>
7 #include <linux/i2c.h>
8 #include <linux/interrupt.h>
9 #include <linux/io.h>
10 #include <linux/module.h>
11 #include <linux/platform_device.h>
12 
13 #define UNIPHIER_I2C_DTRM	0x00	/* TX register */
14 #define     UNIPHIER_I2C_DTRM_IRQEN	BIT(11)	/* enable interrupt */
15 #define     UNIPHIER_I2C_DTRM_STA	BIT(10)	/* start condition */
16 #define     UNIPHIER_I2C_DTRM_STO	BIT(9)	/* stop condition */
17 #define     UNIPHIER_I2C_DTRM_NACK	BIT(8)	/* do not return ACK */
18 #define     UNIPHIER_I2C_DTRM_RD	BIT(0)	/* read transaction */
19 #define UNIPHIER_I2C_DREC	0x04	/* RX register */
20 #define     UNIPHIER_I2C_DREC_MST	BIT(14)	/* 1 = master, 0 = slave */
21 #define     UNIPHIER_I2C_DREC_TX	BIT(13)	/* 1 = transmit, 0 = receive */
22 #define     UNIPHIER_I2C_DREC_STS	BIT(12)	/* stop condition detected */
23 #define     UNIPHIER_I2C_DREC_LRB	BIT(11)	/* no ACK */
24 #define     UNIPHIER_I2C_DREC_LAB	BIT(9)	/* arbitration lost */
25 #define     UNIPHIER_I2C_DREC_BBN	BIT(8)	/* bus not busy */
26 #define UNIPHIER_I2C_MYAD	0x08	/* slave address */
27 #define UNIPHIER_I2C_CLK	0x0c	/* clock frequency control */
28 #define UNIPHIER_I2C_BRST	0x10	/* bus reset */
29 #define     UNIPHIER_I2C_BRST_FOEN	BIT(1)	/* normal operation */
30 #define     UNIPHIER_I2C_BRST_RSCL	BIT(0)	/* release SCL */
31 #define UNIPHIER_I2C_HOLD	0x14	/* hold time control */
32 #define UNIPHIER_I2C_BSTS	0x18	/* bus status monitor */
33 #define     UNIPHIER_I2C_BSTS_SDA	BIT(1)	/* readback of SDA line */
34 #define     UNIPHIER_I2C_BSTS_SCL	BIT(0)	/* readback of SCL line */
35 #define UNIPHIER_I2C_NOISE	0x1c	/* noise filter control */
36 #define UNIPHIER_I2C_SETUP	0x20	/* setup time control */
37 
38 struct uniphier_i2c_priv {
39 	struct completion comp;
40 	struct i2c_adapter adap;
41 	void __iomem *membase;
42 	struct clk *clk;
43 	unsigned int busy_cnt;
44 	unsigned int clk_cycle;
45 };
46 
47 static irqreturn_t uniphier_i2c_interrupt(int irq, void *dev_id)
48 {
49 	struct uniphier_i2c_priv *priv = dev_id;
50 
51 	/*
52 	 * This hardware uses edge triggered interrupt.  Do not touch the
53 	 * hardware registers in this handler to make sure to catch the next
54 	 * interrupt edge.  Just send a complete signal and return.
55 	 */
56 	complete(&priv->comp);
57 
58 	return IRQ_HANDLED;
59 }
60 
61 static int uniphier_i2c_xfer_byte(struct i2c_adapter *adap, u32 txdata,
62 				  u32 *rxdatap)
63 {
64 	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);
65 	unsigned long time_left;
66 	u32 rxdata;
67 
68 	reinit_completion(&priv->comp);
69 
70 	txdata |= UNIPHIER_I2C_DTRM_IRQEN;
71 	writel(txdata, priv->membase + UNIPHIER_I2C_DTRM);
72 
73 	time_left = wait_for_completion_timeout(&priv->comp, adap->timeout);
74 	if (unlikely(!time_left)) {
75 		dev_err(&adap->dev, "transaction timeout\n");
76 		return -ETIMEDOUT;
77 	}
78 
79 	rxdata = readl(priv->membase + UNIPHIER_I2C_DREC);
80 	if (rxdatap)
81 		*rxdatap = rxdata;
82 
83 	return 0;
84 }
85 
86 static int uniphier_i2c_send_byte(struct i2c_adapter *adap, u32 txdata)
87 {
88 	u32 rxdata;
89 	int ret;
90 
91 	ret = uniphier_i2c_xfer_byte(adap, txdata, &rxdata);
92 	if (ret)
93 		return ret;
94 
95 	if (unlikely(rxdata & UNIPHIER_I2C_DREC_LAB))
96 		return -EAGAIN;
97 
98 	if (unlikely(rxdata & UNIPHIER_I2C_DREC_LRB))
99 		return -ENXIO;
100 
101 	return 0;
102 }
103 
104 static int uniphier_i2c_tx(struct i2c_adapter *adap, u16 addr, u16 len,
105 			   const u8 *buf)
106 {
107 	int ret;
108 
109 	ret = uniphier_i2c_send_byte(adap, addr << 1 |
110 				     UNIPHIER_I2C_DTRM_STA |
111 				     UNIPHIER_I2C_DTRM_NACK);
112 	if (ret)
113 		return ret;
114 
115 	while (len--) {
116 		ret = uniphier_i2c_send_byte(adap,
117 					     UNIPHIER_I2C_DTRM_NACK | *buf++);
118 		if (ret)
119 			return ret;
120 	}
121 
122 	return 0;
123 }
124 
125 static int uniphier_i2c_rx(struct i2c_adapter *adap, u16 addr, u16 len,
126 			   u8 *buf)
127 {
128 	int ret;
129 
130 	ret = uniphier_i2c_send_byte(adap, addr << 1 |
131 				     UNIPHIER_I2C_DTRM_STA |
132 				     UNIPHIER_I2C_DTRM_NACK |
133 				     UNIPHIER_I2C_DTRM_RD);
134 	if (ret)
135 		return ret;
136 
137 	while (len--) {
138 		u32 rxdata;
139 
140 		ret = uniphier_i2c_xfer_byte(adap,
141 					     len ? 0 : UNIPHIER_I2C_DTRM_NACK,
142 					     &rxdata);
143 		if (ret)
144 			return ret;
145 		*buf++ = rxdata;
146 	}
147 
148 	return 0;
149 }
150 
151 static int uniphier_i2c_stop(struct i2c_adapter *adap)
152 {
153 	return uniphier_i2c_send_byte(adap, UNIPHIER_I2C_DTRM_STO |
154 				      UNIPHIER_I2C_DTRM_NACK);
155 }
156 
157 static int uniphier_i2c_master_xfer_one(struct i2c_adapter *adap,
158 					struct i2c_msg *msg, bool stop)
159 {
160 	bool is_read = msg->flags & I2C_M_RD;
161 	bool recovery = false;
162 	int ret;
163 
164 	if (is_read)
165 		ret = uniphier_i2c_rx(adap, msg->addr, msg->len, msg->buf);
166 	else
167 		ret = uniphier_i2c_tx(adap, msg->addr, msg->len, msg->buf);
168 
169 	if (ret == -EAGAIN) /* could not acquire bus. bail out without STOP */
170 		return ret;
171 
172 	if (ret == -ETIMEDOUT) {
173 		/* This error is fatal.  Needs recovery. */
174 		stop = false;
175 		recovery = true;
176 	}
177 
178 	if (stop) {
179 		int ret2 = uniphier_i2c_stop(adap);
180 
181 		if (ret2) {
182 			/* Failed to issue STOP.  The bus needs recovery. */
183 			recovery = true;
184 			ret = ret ?: ret2;
185 		}
186 	}
187 
188 	if (recovery)
189 		i2c_recover_bus(adap);
190 
191 	return ret;
192 }
193 
194 static int uniphier_i2c_check_bus_busy(struct i2c_adapter *adap)
195 {
196 	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);
197 
198 	if (!(readl(priv->membase + UNIPHIER_I2C_DREC) &
199 						UNIPHIER_I2C_DREC_BBN)) {
200 		if (priv->busy_cnt++ > 3) {
201 			/*
202 			 * If bus busy continues too long, it is probably
203 			 * in a wrong state.  Try bus recovery.
204 			 */
205 			i2c_recover_bus(adap);
206 			priv->busy_cnt = 0;
207 		}
208 
209 		return -EAGAIN;
210 	}
211 
212 	priv->busy_cnt = 0;
213 	return 0;
214 }
215 
216 static int uniphier_i2c_master_xfer(struct i2c_adapter *adap,
217 				    struct i2c_msg *msgs, int num)
218 {
219 	struct i2c_msg *msg, *emsg = msgs + num;
220 	int ret;
221 
222 	ret = uniphier_i2c_check_bus_busy(adap);
223 	if (ret)
224 		return ret;
225 
226 	for (msg = msgs; msg < emsg; msg++) {
227 		/* Emit STOP if it is the last message or I2C_M_STOP is set. */
228 		bool stop = (msg + 1 == emsg) || (msg->flags & I2C_M_STOP);
229 
230 		ret = uniphier_i2c_master_xfer_one(adap, msg, stop);
231 		if (ret)
232 			return ret;
233 	}
234 
235 	return num;
236 }
237 
238 static u32 uniphier_i2c_functionality(struct i2c_adapter *adap)
239 {
240 	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
241 }
242 
243 static const struct i2c_algorithm uniphier_i2c_algo = {
244 	.master_xfer = uniphier_i2c_master_xfer,
245 	.functionality = uniphier_i2c_functionality,
246 };
247 
248 static void uniphier_i2c_reset(struct uniphier_i2c_priv *priv, bool reset_on)
249 {
250 	u32 val = UNIPHIER_I2C_BRST_RSCL;
251 
252 	val |= reset_on ? 0 : UNIPHIER_I2C_BRST_FOEN;
253 	writel(val, priv->membase + UNIPHIER_I2C_BRST);
254 }
255 
256 static int uniphier_i2c_get_scl(struct i2c_adapter *adap)
257 {
258 	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);
259 
260 	return !!(readl(priv->membase + UNIPHIER_I2C_BSTS) &
261 							UNIPHIER_I2C_BSTS_SCL);
262 }
263 
264 static void uniphier_i2c_set_scl(struct i2c_adapter *adap, int val)
265 {
266 	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);
267 
268 	writel(val ? UNIPHIER_I2C_BRST_RSCL : 0,
269 	       priv->membase + UNIPHIER_I2C_BRST);
270 }
271 
272 static int uniphier_i2c_get_sda(struct i2c_adapter *adap)
273 {
274 	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);
275 
276 	return !!(readl(priv->membase + UNIPHIER_I2C_BSTS) &
277 							UNIPHIER_I2C_BSTS_SDA);
278 }
279 
280 static void uniphier_i2c_unprepare_recovery(struct i2c_adapter *adap)
281 {
282 	uniphier_i2c_reset(i2c_get_adapdata(adap), false);
283 }
284 
285 static struct i2c_bus_recovery_info uniphier_i2c_bus_recovery_info = {
286 	.recover_bus = i2c_generic_scl_recovery,
287 	.get_scl = uniphier_i2c_get_scl,
288 	.set_scl = uniphier_i2c_set_scl,
289 	.get_sda = uniphier_i2c_get_sda,
290 	.unprepare_recovery = uniphier_i2c_unprepare_recovery,
291 };
292 
293 static void uniphier_i2c_hw_init(struct uniphier_i2c_priv *priv)
294 {
295 	unsigned int cyc = priv->clk_cycle;
296 
297 	uniphier_i2c_reset(priv, true);
298 
299 	/*
300 	 * Bit30-16: clock cycles of tLOW.
301 	 *  Standard-mode: tLOW = 4.7 us, tHIGH = 4.0 us
302 	 *  Fast-mode:     tLOW = 1.3 us, tHIGH = 0.6 us
303 	 * "tLow/tHIGH = 5/4" meets both.
304 	 */
305 	writel((cyc * 5 / 9 << 16) | cyc, priv->membase + UNIPHIER_I2C_CLK);
306 
307 	uniphier_i2c_reset(priv, false);
308 }
309 
310 static int uniphier_i2c_probe(struct platform_device *pdev)
311 {
312 	struct device *dev = &pdev->dev;
313 	struct uniphier_i2c_priv *priv;
314 	u32 bus_speed;
315 	unsigned long clk_rate;
316 	int irq, ret;
317 
318 	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
319 	if (!priv)
320 		return -ENOMEM;
321 
322 	priv->membase = devm_platform_ioremap_resource(pdev, 0);
323 	if (IS_ERR(priv->membase))
324 		return PTR_ERR(priv->membase);
325 
326 	irq = platform_get_irq(pdev, 0);
327 	if (irq < 0)
328 		return irq;
329 
330 	if (of_property_read_u32(dev->of_node, "clock-frequency", &bus_speed))
331 		bus_speed = I2C_MAX_STANDARD_MODE_FREQ;
332 
333 	if (!bus_speed || bus_speed > I2C_MAX_FAST_MODE_FREQ) {
334 		dev_err(dev, "invalid clock-frequency %d\n", bus_speed);
335 		return -EINVAL;
336 	}
337 
338 	priv->clk = devm_clk_get_enabled(dev, NULL);
339 	if (IS_ERR(priv->clk)) {
340 		dev_err(dev, "failed to enable clock\n");
341 		return PTR_ERR(priv->clk);
342 	}
343 
344 	clk_rate = clk_get_rate(priv->clk);
345 	if (!clk_rate) {
346 		dev_err(dev, "input clock rate should not be zero\n");
347 		return -EINVAL;
348 	}
349 
350 	priv->clk_cycle = clk_rate / bus_speed;
351 	init_completion(&priv->comp);
352 	priv->adap.owner = THIS_MODULE;
353 	priv->adap.algo = &uniphier_i2c_algo;
354 	priv->adap.dev.parent = dev;
355 	priv->adap.dev.of_node = dev->of_node;
356 	strscpy(priv->adap.name, "UniPhier I2C", sizeof(priv->adap.name));
357 	priv->adap.bus_recovery_info = &uniphier_i2c_bus_recovery_info;
358 	i2c_set_adapdata(&priv->adap, priv);
359 	platform_set_drvdata(pdev, priv);
360 
361 	uniphier_i2c_hw_init(priv);
362 
363 	ret = devm_request_irq(dev, irq, uniphier_i2c_interrupt, 0, pdev->name,
364 			       priv);
365 	if (ret) {
366 		dev_err(dev, "failed to request irq %d\n", irq);
367 		return ret;
368 	}
369 
370 	return i2c_add_adapter(&priv->adap);
371 }
372 
373 static void uniphier_i2c_remove(struct platform_device *pdev)
374 {
375 	struct uniphier_i2c_priv *priv = platform_get_drvdata(pdev);
376 
377 	i2c_del_adapter(&priv->adap);
378 }
379 
380 static int __maybe_unused uniphier_i2c_suspend(struct device *dev)
381 {
382 	struct uniphier_i2c_priv *priv = dev_get_drvdata(dev);
383 
384 	clk_disable_unprepare(priv->clk);
385 
386 	return 0;
387 }
388 
389 static int __maybe_unused uniphier_i2c_resume(struct device *dev)
390 {
391 	struct uniphier_i2c_priv *priv = dev_get_drvdata(dev);
392 	int ret;
393 
394 	ret = clk_prepare_enable(priv->clk);
395 	if (ret)
396 		return ret;
397 
398 	uniphier_i2c_hw_init(priv);
399 
400 	return 0;
401 }
402 
403 static const struct dev_pm_ops uniphier_i2c_pm_ops = {
404 	SET_SYSTEM_SLEEP_PM_OPS(uniphier_i2c_suspend, uniphier_i2c_resume)
405 };
406 
407 static const struct of_device_id uniphier_i2c_match[] = {
408 	{ .compatible = "socionext,uniphier-i2c" },
409 	{ /* sentinel */ }
410 };
411 MODULE_DEVICE_TABLE(of, uniphier_i2c_match);
412 
413 static struct platform_driver uniphier_i2c_drv = {
414 	.probe  = uniphier_i2c_probe,
415 	.remove_new = uniphier_i2c_remove,
416 	.driver = {
417 		.name  = "uniphier-i2c",
418 		.of_match_table = uniphier_i2c_match,
419 		.pm = &uniphier_i2c_pm_ops,
420 	},
421 };
422 module_platform_driver(uniphier_i2c_drv);
423 
424 MODULE_AUTHOR("Masahiro Yamada <yamada.masahiro@socionext.com>");
425 MODULE_DESCRIPTION("UniPhier I2C bus driver");
426 MODULE_LICENSE("GPL");
427