1/*
  2 * Copyright (C) 2015 Masahiro Yamada <yamada.masahiro@socionext.com>
  3 *
  4 * This program is free software; you can redistribute it and/or modify
  5 * it under the terms of the GNU General Public License as published by
  6 * the Free Software Foundation; either version 2 of the License, or
  7 * (at your option) any later version.
  8 *
  9 * This program is distributed in the hope that it will be useful,
 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 12 * GNU General Public License for more details.
 13 */
 14
 15#include <linux/clk.h>
 16#include <linux/i2c.h>
 17#include <linux/interrupt.h>
 18#include <linux/io.h>
 19#include <linux/module.h>
 20#include <linux/platform_device.h>
 21
 22#define UNIPHIER_I2C_DTRM	0x00	/* TX register */
 23#define     UNIPHIER_I2C_DTRM_IRQEN	BIT(11)	/* enable interrupt */
 24#define     UNIPHIER_I2C_DTRM_STA	BIT(10)	/* start condition */
 25#define     UNIPHIER_I2C_DTRM_STO	BIT(9)	/* stop condition */
 26#define     UNIPHIER_I2C_DTRM_NACK	BIT(8)	/* do not return ACK */
 27#define     UNIPHIER_I2C_DTRM_RD	BIT(0)	/* read transaction */
 28#define UNIPHIER_I2C_DREC	0x04	/* RX register */
 29#define     UNIPHIER_I2C_DREC_MST	BIT(14)	/* 1 = master, 0 = slave */
 30#define     UNIPHIER_I2C_DREC_TX	BIT(13)	/* 1 = transmit, 0 = receive */
 31#define     UNIPHIER_I2C_DREC_STS	BIT(12)	/* stop condition detected */
 32#define     UNIPHIER_I2C_DREC_LRB	BIT(11)	/* no ACK */
 33#define     UNIPHIER_I2C_DREC_LAB	BIT(9)	/* arbitration lost */
 34#define     UNIPHIER_I2C_DREC_BBN	BIT(8)	/* bus not busy */
 35#define UNIPHIER_I2C_MYAD	0x08	/* slave address */
 36#define UNIPHIER_I2C_CLK	0x0c	/* clock frequency control */
 37#define UNIPHIER_I2C_BRST	0x10	/* bus reset */
 38#define     UNIPHIER_I2C_BRST_FOEN	BIT(1)	/* normal operation */
 39#define     UNIPHIER_I2C_BRST_RSCL	BIT(0)	/* release SCL */
 40#define UNIPHIER_I2C_HOLD	0x14	/* hold time control */
 41#define UNIPHIER_I2C_BSTS	0x18	/* bus status monitor */
 42#define     UNIPHIER_I2C_BSTS_SDA	BIT(1)	/* readback of SDA line */
 43#define     UNIPHIER_I2C_BSTS_SCL	BIT(0)	/* readback of SCL line */
 44#define UNIPHIER_I2C_NOISE	0x1c	/* noise filter control */
 45#define UNIPHIER_I2C_SETUP	0x20	/* setup time control */
 46
 47#define UNIPHIER_I2C_DEFAULT_SPEED	100000
 48#define UNIPHIER_I2C_MAX_SPEED		400000
 49
 50struct uniphier_i2c_priv {
 51	struct completion comp;
 52	struct i2c_adapter adap;
 53	void __iomem *membase;
 54	struct clk *clk;
 55	unsigned int busy_cnt;
 56};
 57
 58static irqreturn_t uniphier_i2c_interrupt(int irq, void *dev_id)
 59{
 60	struct uniphier_i2c_priv *priv = dev_id;
 61
 62	/*
 63	 * This hardware uses edge triggered interrupt.  Do not touch the
 64	 * hardware registers in this handler to make sure to catch the next
 65	 * interrupt edge.  Just send a complete signal and return.
 66	 */
 67	complete(&priv->comp);
 68
 69	return IRQ_HANDLED;
 70}
 71
 72static int uniphier_i2c_xfer_byte(struct i2c_adapter *adap, u32 txdata,
 73				  u32 *rxdatap)
 74{
 75	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);
 76	unsigned long time_left;
 77	u32 rxdata;
 78
 79	reinit_completion(&priv->comp);
 80
 81	txdata |= UNIPHIER_I2C_DTRM_IRQEN;
 82	dev_dbg(&adap->dev, "write data: 0x%04x\n", txdata);
 83	writel(txdata, priv->membase + UNIPHIER_I2C_DTRM);
 84
 85	time_left = wait_for_completion_timeout(&priv->comp, adap->timeout);
 86	if (unlikely(!time_left)) {
 87		dev_err(&adap->dev, "transaction timeout\n");
 88		return -ETIMEDOUT;
 89	}
 90
 91	rxdata = readl(priv->membase + UNIPHIER_I2C_DREC);
 92	dev_dbg(&adap->dev, "read data: 0x%04x\n", rxdata);
 93
 94	if (rxdatap)
 95		*rxdatap = rxdata;
 96
 97	return 0;
 98}
 99
100static int uniphier_i2c_send_byte(struct i2c_adapter *adap, u32 txdata)
101{
102	u32 rxdata;
103	int ret;
104
105	ret = uniphier_i2c_xfer_byte(adap, txdata, &rxdata);
106	if (ret)
107		return ret;
108
109	if (unlikely(rxdata & UNIPHIER_I2C_DREC_LAB)) {
110		dev_dbg(&adap->dev, "arbitration lost\n");
111		return -EAGAIN;
112	}
113	if (unlikely(rxdata & UNIPHIER_I2C_DREC_LRB)) {
114		dev_dbg(&adap->dev, "could not get ACK\n");
115		return -ENXIO;
116	}
117
118	return 0;
119}
120
121static int uniphier_i2c_tx(struct i2c_adapter *adap, u16 addr, u16 len,
122			   const u8 *buf)
123{
124	int ret;
125
126	dev_dbg(&adap->dev, "start condition\n");
127	ret = uniphier_i2c_send_byte(adap, addr << 1 |
128				     UNIPHIER_I2C_DTRM_STA |
129				     UNIPHIER_I2C_DTRM_NACK);
130	if (ret)
131		return ret;
132
133	while (len--) {
134		ret = uniphier_i2c_send_byte(adap,
135					     UNIPHIER_I2C_DTRM_NACK | *buf++);
136		if (ret)
137			return ret;
138	}
139
140	return 0;
141}
142
143static int uniphier_i2c_rx(struct i2c_adapter *adap, u16 addr, u16 len,
144			   u8 *buf)
145{
146	int ret;
147
148	dev_dbg(&adap->dev, "start condition\n");
149	ret = uniphier_i2c_send_byte(adap, addr << 1 |
150				     UNIPHIER_I2C_DTRM_STA |
151				     UNIPHIER_I2C_DTRM_NACK |
152				     UNIPHIER_I2C_DTRM_RD);
153	if (ret)
154		return ret;
155
156	while (len--) {
157		u32 rxdata;
158
159		ret = uniphier_i2c_xfer_byte(adap,
160					     len ? 0 : UNIPHIER_I2C_DTRM_NACK,
161					     &rxdata);
162		if (ret)
163			return ret;
164		*buf++ = rxdata;
165	}
166
167	return 0;
168}
169
170static int uniphier_i2c_stop(struct i2c_adapter *adap)
171{
172	dev_dbg(&adap->dev, "stop condition\n");
173	return uniphier_i2c_send_byte(adap, UNIPHIER_I2C_DTRM_STO |
174				      UNIPHIER_I2C_DTRM_NACK);
175}
176
177static int uniphier_i2c_master_xfer_one(struct i2c_adapter *adap,
178					struct i2c_msg *msg, bool stop)
179{
180	bool is_read = msg->flags & I2C_M_RD;
181	bool recovery = false;
182	int ret;
183
184	dev_dbg(&adap->dev, "%s: addr=0x%02x, len=%d, stop=%d\n",
185		is_read ? "receive" : "transmit", msg->addr, msg->len, stop);
186
187	if (is_read)
188		ret = uniphier_i2c_rx(adap, msg->addr, msg->len, msg->buf);
189	else
190		ret = uniphier_i2c_tx(adap, msg->addr, msg->len, msg->buf);
191
192	if (ret == -EAGAIN) /* could not acquire bus. bail out without STOP */
193		return ret;
194
195	if (ret == -ETIMEDOUT) {
196		/* This error is fatal.  Needs recovery. */
197		stop = false;
198		recovery = true;
199	}
200
201	if (stop) {
202		int ret2 = uniphier_i2c_stop(adap);
203
204		if (ret2) {
205			/* Failed to issue STOP.  The bus needs recovery. */
206			recovery = true;
207			ret = ret ?: ret2;
208		}
209	}
210
211	if (recovery)
212		i2c_recover_bus(adap);
213
214	return ret;
215}
216
217static int uniphier_i2c_check_bus_busy(struct i2c_adapter *adap)
218{
219	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);
220
221	if (!(readl(priv->membase + UNIPHIER_I2C_DREC) &
222						UNIPHIER_I2C_DREC_BBN)) {
223		if (priv->busy_cnt++ > 3) {
224			/*
225			 * If bus busy continues too long, it is probably
226			 * in a wrong state.  Try bus recovery.
227			 */
228			i2c_recover_bus(adap);
229			priv->busy_cnt = 0;
230		}
231
232		return -EAGAIN;
233	}
234
235	priv->busy_cnt = 0;
236	return 0;
237}
238
239static int uniphier_i2c_master_xfer(struct i2c_adapter *adap,
240				    struct i2c_msg *msgs, int num)
241{
242	struct i2c_msg *msg, *emsg = msgs + num;
243	int ret;
244
245	ret = uniphier_i2c_check_bus_busy(adap);
246	if (ret)
247		return ret;
248
249	for (msg = msgs; msg < emsg; msg++) {
250		/* If next message is read, skip the stop condition */
251		bool stop = !(msg + 1 < emsg && msg[1].flags & I2C_M_RD);
252		/* but, force it if I2C_M_STOP is set */
253		if (msg->flags & I2C_M_STOP)
254			stop = true;
255
256		ret = uniphier_i2c_master_xfer_one(adap, msg, stop);
257		if (ret)
258			return ret;
259	}
260
261	return num;
262}
263
264static u32 uniphier_i2c_functionality(struct i2c_adapter *adap)
265{
266	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
267}
268
269static const struct i2c_algorithm uniphier_i2c_algo = {
270	.master_xfer = uniphier_i2c_master_xfer,
271	.functionality = uniphier_i2c_functionality,
272};
273
274static void uniphier_i2c_reset(struct uniphier_i2c_priv *priv, bool reset_on)
275{
276	u32 val = UNIPHIER_I2C_BRST_RSCL;
277
278	val |= reset_on ? 0 : UNIPHIER_I2C_BRST_FOEN;
279	writel(val, priv->membase + UNIPHIER_I2C_BRST);
280}
281
282static int uniphier_i2c_get_scl(struct i2c_adapter *adap)
283{
284	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);
285
286	return !!(readl(priv->membase + UNIPHIER_I2C_BSTS) &
287							UNIPHIER_I2C_BSTS_SCL);
288}
289
290static void uniphier_i2c_set_scl(struct i2c_adapter *adap, int val)
291{
292	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);
293
294	writel(val ? UNIPHIER_I2C_BRST_RSCL : 0,
295	       priv->membase + UNIPHIER_I2C_BRST);
296}
297
298static int uniphier_i2c_get_sda(struct i2c_adapter *adap)
299{
300	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);
301
302	return !!(readl(priv->membase + UNIPHIER_I2C_BSTS) &
303							UNIPHIER_I2C_BSTS_SDA);
304}
305
306static void uniphier_i2c_unprepare_recovery(struct i2c_adapter *adap)
307{
308	uniphier_i2c_reset(i2c_get_adapdata(adap), false);
309}
310
311static struct i2c_bus_recovery_info uniphier_i2c_bus_recovery_info = {
312	.recover_bus = i2c_generic_scl_recovery,
313	.get_scl = uniphier_i2c_get_scl,
314	.set_scl = uniphier_i2c_set_scl,
315	.get_sda = uniphier_i2c_get_sda,
316	.unprepare_recovery = uniphier_i2c_unprepare_recovery,
317};
318
319static void uniphier_i2c_hw_init(struct uniphier_i2c_priv *priv,
320				 u32 bus_speed, unsigned long clk_rate)
321{
322	uniphier_i2c_reset(priv, true);
323
324	writel((clk_rate / bus_speed / 2 << 16) | (clk_rate / bus_speed),
325	       priv->membase + UNIPHIER_I2C_CLK);
326
327	uniphier_i2c_reset(priv, false);
328}
329
330static int uniphier_i2c_probe(struct platform_device *pdev)
331{
332	struct device *dev = &pdev->dev;
333	struct uniphier_i2c_priv *priv;
334	struct resource *regs;
335	u32 bus_speed;
336	unsigned long clk_rate;
337	int irq, ret;
338
339	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
340	if (!priv)
341		return -ENOMEM;
342
343	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
344	priv->membase = devm_ioremap_resource(dev, regs);
345	if (IS_ERR(priv->membase))
346		return PTR_ERR(priv->membase);
347
348	irq = platform_get_irq(pdev, 0);
349	if (irq < 0) {
350		dev_err(dev, "failed to get IRQ number\n");
351		return irq;
352	}
353
354	if (of_property_read_u32(dev->of_node, "clock-frequency", &bus_speed))
355		bus_speed = UNIPHIER_I2C_DEFAULT_SPEED;
356
357	if (!bus_speed || bus_speed > UNIPHIER_I2C_MAX_SPEED) {
358		dev_err(dev, "invalid clock-frequency %d\n", bus_speed);
359		return -EINVAL;
360	}
361
362	priv->clk = devm_clk_get(dev, NULL);
363	if (IS_ERR(priv->clk)) {
364		dev_err(dev, "failed to get clock\n");
365		return PTR_ERR(priv->clk);
366	}
367
368	ret = clk_prepare_enable(priv->clk);
369	if (ret)
370		return ret;
371
372	clk_rate = clk_get_rate(priv->clk);
373	if (!clk_rate) {
374		dev_err(dev, "input clock rate should not be zero\n");
375		ret = -EINVAL;
376		goto disable_clk;
377	}
378
379	init_completion(&priv->comp);
380	priv->adap.owner = THIS_MODULE;
381	priv->adap.algo = &uniphier_i2c_algo;
382	priv->adap.dev.parent = dev;
383	priv->adap.dev.of_node = dev->of_node;
384	strlcpy(priv->adap.name, "UniPhier I2C", sizeof(priv->adap.name));
385	priv->adap.bus_recovery_info = &uniphier_i2c_bus_recovery_info;
386	i2c_set_adapdata(&priv->adap, priv);
387	platform_set_drvdata(pdev, priv);
388
389	uniphier_i2c_hw_init(priv, bus_speed, clk_rate);
390
391	ret = devm_request_irq(dev, irq, uniphier_i2c_interrupt, 0, pdev->name,
392			       priv);
393	if (ret) {
394		dev_err(dev, "failed to request irq %d\n", irq);
395		goto disable_clk;
396	}
397
398	ret = i2c_add_adapter(&priv->adap);
399disable_clk:
400	if (ret)
401		clk_disable_unprepare(priv->clk);
402
403	return ret;
404}
405
406static int uniphier_i2c_remove(struct platform_device *pdev)
407{
408	struct uniphier_i2c_priv *priv = platform_get_drvdata(pdev);
409
410	i2c_del_adapter(&priv->adap);
411	clk_disable_unprepare(priv->clk);
412
413	return 0;
414}
415
416static const struct of_device_id uniphier_i2c_match[] = {
417	{ .compatible = "socionext,uniphier-i2c" },
418	{ /* sentinel */ }
419};
420MODULE_DEVICE_TABLE(of, uniphier_i2c_match);
421
422static struct platform_driver uniphier_i2c_drv = {
423	.probe  = uniphier_i2c_probe,
424	.remove = uniphier_i2c_remove,
425	.driver = {
426		.name  = "uniphier-i2c",
427		.of_match_table = uniphier_i2c_match,
428	},
429};
430module_platform_driver(uniphier_i2c_drv);
431
432MODULE_AUTHOR("Masahiro Yamada <yamada.masahiro@socionext.com>");
433MODULE_DESCRIPTION("UniPhier I2C bus driver");
434MODULE_LICENSE("GPL");