summaryrefslogtreecommitdiffstats
path: root/drivers/i2c/busses/i2c-bcm2835.c
blob: c9336a3202d5620681b38d6e8c2b47651a75af0e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
/*
 * BCM2835 master mode driver
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/clk.h>
#include <linux/completion.h>
#include <linux/err.h>
#include <linux/i2c.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/slab.h>

#define BCM2835_I2C_C		0x0
#define BCM2835_I2C_S		0x4
#define BCM2835_I2C_DLEN	0x8
#define BCM2835_I2C_A		0xc
#define BCM2835_I2C_FIFO	0x10
#define BCM2835_I2C_DIV		0x14
#define BCM2835_I2C_DEL		0x18
#define BCM2835_I2C_CLKT	0x1c

#define BCM2835_I2C_C_READ	BIT(0)
#define BCM2835_I2C_C_CLEAR	BIT(4) /* bits 4 and 5 both clear */
#define BCM2835_I2C_C_ST	BIT(7)
#define BCM2835_I2C_C_INTD	BIT(8)
#define BCM2835_I2C_C_INTT	BIT(9)
#define BCM2835_I2C_C_INTR	BIT(10)
#define BCM2835_I2C_C_I2CEN	BIT(15)

#define BCM2835_I2C_S_TA	BIT(0)
#define BCM2835_I2C_S_DONE	BIT(1)
#define BCM2835_I2C_S_TXW	BIT(2)
#define BCM2835_I2C_S_RXR	BIT(3)
#define BCM2835_I2C_S_TXD	BIT(4)
#define BCM2835_I2C_S_RXD	BIT(5)
#define BCM2835_I2C_S_TXE	BIT(6)
#define BCM2835_I2C_S_RXF	BIT(7)
#define BCM2835_I2C_S_ERR	BIT(8)
#define BCM2835_I2C_S_CLKT	BIT(9)
#define BCM2835_I2C_S_LEN	BIT(10) /* Fake bit for SW error reporting */

#define BCM2835_I2C_TIMEOUT (msecs_to_jiffies(1000))

struct bcm2835_i2c_dev {
	struct device *dev;
	void __iomem *regs;
	struct clk *clk;
	int irq;
	struct i2c_adapter adapter;
	struct completion completion;
	u32 msg_err;
	u8 *msg_buf;
	size_t msg_buf_remaining;
};

static inline void bcm2835_i2c_writel(struct bcm2835_i2c_dev *i2c_dev,
				      u32 reg, u32 val)
{
	writel(val, i2c_dev->regs + reg);
}

static inline u32 bcm2835_i2c_readl(struct bcm2835_i2c_dev *i2c_dev, u32 reg)
{
	return readl(i2c_dev->regs + reg);
}

static void bcm2835_fill_txfifo(struct bcm2835_i2c_dev *i2c_dev)
{
	u32 val;

	while (i2c_dev->msg_buf_remaining) {
		val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
		if (!(val & BCM2835_I2C_S_TXD))
			break;
		bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_FIFO,
				   *i2c_dev->msg_buf);
		i2c_dev->msg_buf++;
		i2c_dev->msg_buf_remaining--;
	}
}

static void bcm2835_drain_rxfifo(struct bcm2835_i2c_dev *i2c_dev)
{
	u32 val;

	while (i2c_dev->msg_buf_remaining) {
		val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
		if (!(val & BCM2835_I2C_S_RXD))
			break;
		*i2c_dev->msg_buf = bcm2835_i2c_readl(i2c_dev,
						      BCM2835_I2C_FIFO);
		i2c_dev->msg_buf++;
		i2c_dev->msg_buf_remaining--;
	}
}

static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data)
{
	struct bcm2835_i2c_dev *i2c_dev = data;
	u32 val, err;

	val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_S, val);

	err = val & (BCM2835_I2C_S_CLKT | BCM2835_I2C_S_ERR);
	if (err) {
		i2c_dev->msg_err = err;
		complete(&i2c_dev->completion);
		return IRQ_HANDLED;
	}

	if (val & BCM2835_I2C_S_RXD) {
		bcm2835_drain_rxfifo(i2c_dev);
		if (!(val & BCM2835_I2C_S_DONE))
			return IRQ_HANDLED;
	}

	if (val & BCM2835_I2C_S_DONE) {
		if (i2c_dev->msg_buf_remaining)
			i2c_dev->msg_err = BCM2835_I2C_S_LEN;
		else
			i2c_dev->msg_err = 0;
		complete(&i2c_dev->completion);
		return IRQ_HANDLED;
	}

	if (val & BCM2835_I2C_S_TXD) {
		bcm2835_fill_txfifo(i2c_dev);
		return IRQ_HANDLED;
	}

	return IRQ_NONE;
}

static int bcm2835_i2c_xfer_msg(struct bcm2835_i2c_dev *i2c_dev,
				struct i2c_msg *msg)
{
	u32 c;
	unsigned long time_left;

	i2c_dev->msg_buf = msg->buf;
	i2c_dev->msg_buf_remaining = msg->len;
	reinit_completion(&i2c_dev->completion);

	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, BCM2835_I2C_C_CLEAR);

	if (msg->flags & I2C_M_RD) {
		c = BCM2835_I2C_C_READ | BCM2835_I2C_C_INTR;
	} else {
		c = BCM2835_I2C_C_INTT;
		bcm2835_fill_txfifo(i2c_dev);
	}
	c |= BCM2835_I2C_C_ST | BCM2835_I2C_C_INTD | BCM2835_I2C_C_I2CEN;

	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_A, msg->addr);
	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DLEN, msg->len);
	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, c);

	time_left = wait_for_completion_timeout(&i2c_dev->completion,
						BCM2835_I2C_TIMEOUT);
	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, BCM2835_I2C_C_CLEAR);
	if (!time_left) {
		dev_err(i2c_dev->dev, "i2c transfer timed out\n");
		return -ETIMEDOUT;
	}

	if (likely(!i2c_dev->msg_err))
		return 0;

	if ((i2c_dev->msg_err & BCM2835_I2C_S_ERR) &&
	    (msg->flags & I2C_M_IGNORE_NAK))
		return 0;

	dev_err(i2c_dev->dev, "i2c transfer failed: %x\n", i2c_dev->msg_err);

	if (i2c_dev->msg_err & BCM2835_I2C_S_ERR)
		return -EREMOTEIO;
	else
		return -EIO;
}

static int bcm2835_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
			    int num)
{
	struct bcm2835_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
	int i;
	int ret = 0;

	for (i = 0; i < num; i++) {
		ret = bcm2835_i2c_xfer_msg(i2c_dev, &msgs[i]);
		if (ret)
			break;
	}

	return ret ?: i;
}

static u32 bcm2835_i2c_func(struct i2c_adapter *adap)
{
	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
}

static const struct i2c_algorithm bcm2835_i2c_algo = {
	.master_xfer	= bcm2835_i2c_xfer,
	.functionality	= bcm2835_i2c_func,
};

static int bcm2835_i2c_probe(struct platform_device *pdev)
{
	struct bcm2835_i2c_dev *i2c_dev;
	struct resource *mem, *irq;
	u32 bus_clk_rate, divider;
	int ret;
	struct i2c_adapter *adap;

	i2c_dev = devm_kzalloc(&pdev->dev, sizeof(*i2c_dev), GFP_KERNEL);
	if (!i2c_dev)
		return -ENOMEM;
	platform_set_drvdata(pdev, i2c_dev);
	i2c_dev->dev = &pdev->dev;
	init_completion(&i2c_dev->completion);

	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	i2c_dev->regs = devm_ioremap_resource(&pdev->dev, mem);
	if (IS_ERR(i2c_dev->regs))
		return PTR_ERR(i2c_dev->regs);

	i2c_dev->clk = devm_clk_get(&pdev->dev, NULL);
	if (IS_ERR(i2c_dev->clk)) {
		dev_err(&pdev->dev, "Could not get clock\n");
		return PTR_ERR(i2c_dev->clk);
	}

	ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency",
				   &bus_clk_rate);
	if (ret < 0) {
		dev_warn(&pdev->dev,
			 "Could not read clock-frequency property\n");
		bus_clk_rate = 100000;
	}

	divider = DIV_ROUND_UP(clk_get_rate(i2c_dev->clk), bus_clk_rate);
	/*
	 * Per the datasheet, the register is always interpreted as an even
	 * number, by rounding down. In other words, the LSB is ignored. So,
	 * if the LSB is set, increment the divider to avoid any issue.
	 */
	if (divider & 1)
		divider++;
	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DIV, divider);

	irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
	if (!irq) {
		dev_err(&pdev->dev, "No IRQ resource\n");
		return -ENODEV;
	}
	i2c_dev->irq = irq->start;

	ret = request_irq(i2c_dev->irq, bcm2835_i2c_isr, IRQF_SHARED,
			  dev_name(&pdev->dev), i2c_dev);
	if (ret) {
		dev_err(&pdev->dev, "Could not request IRQ\n");
		return -ENODEV;
	}

	adap = &i2c_dev->adapter;
	i2c_set_adapdata(adap, i2c_dev);
	adap->owner = THIS_MODULE;
	adap->class = I2C_CLASS_DEPRECATED;
	strlcpy(adap->name, "bcm2835 I2C adapter", sizeof(adap->name));
	adap->algo = &bcm2835_i2c_algo;
	adap->dev.parent = &pdev->dev;
	adap->dev.of_node = pdev->dev.of_node;

	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, 0);

	ret = i2c_add_adapter(adap);
	if (ret)
		free_irq(i2c_dev->irq, i2c_dev);

	return ret;
}

static int bcm2835_i2c_remove(struct platform_device *pdev)
{
	struct bcm2835_i2c_dev *i2c_dev = platform_get_drvdata(pdev);

	free_irq(i2c_dev->irq, i2c_dev);
	i2c_del_adapter(&i2c_dev->adapter);

	return 0;
}

static const struct of_device_id bcm2835_i2c_of_match[] = {
	{ .compatible = "brcm,bcm2835-i2c" },
	{},
};
MODULE_DEVICE_TABLE(of, bcm2835_i2c_of_match);

static struct platform_driver bcm2835_i2c_driver = {
	.probe		= bcm2835_i2c_probe,
	.remove		= bcm2835_i2c_remove,
	.driver		= {
		.name	= "i2c-bcm2835",
		.of_match_table = bcm2835_i2c_of_match,
	},
};
module_platform_driver(bcm2835_i2c_driver);

MODULE_AUTHOR("Stephen Warren <swarren@wwwdotorg.org>");
MODULE_DESCRIPTION("BCM2835 I2C bus adapter");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("platform:i2c-bcm2835");