1/*
2 * BCM2835 master mode driver
3 *
4 * This software is licensed under the terms of the GNU General Public
5 * License version 2, as published by the Free Software Foundation, and
6 * may be copied, distributed, and modified under those terms.
7 *
8 * This program is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
11 * GNU General Public License for more details.
12 */
13
14#include <linux/clk.h>
15#include <linux/completion.h>
16#include <linux/err.h>
17#include <linux/i2c.h>
18#include <linux/interrupt.h>
19#include <linux/io.h>
20#include <linux/module.h>
21#include <linux/platform_device.h>
22#include <linux/slab.h>
23
24#define BCM2835_I2C_C		0x0
25#define BCM2835_I2C_S		0x4
26#define BCM2835_I2C_DLEN	0x8
27#define BCM2835_I2C_A		0xc
28#define BCM2835_I2C_FIFO	0x10
29#define BCM2835_I2C_DIV		0x14
30#define BCM2835_I2C_DEL		0x18
31#define BCM2835_I2C_CLKT	0x1c
32
33#define BCM2835_I2C_C_READ	BIT(0)
34#define BCM2835_I2C_C_CLEAR	BIT(4) /* bits 4 and 5 both clear */
35#define BCM2835_I2C_C_ST	BIT(7)
36#define BCM2835_I2C_C_INTD	BIT(8)
37#define BCM2835_I2C_C_INTT	BIT(9)
38#define BCM2835_I2C_C_INTR	BIT(10)
39#define BCM2835_I2C_C_I2CEN	BIT(15)
40
41#define BCM2835_I2C_S_TA	BIT(0)
42#define BCM2835_I2C_S_DONE	BIT(1)
43#define BCM2835_I2C_S_TXW	BIT(2)
44#define BCM2835_I2C_S_RXR	BIT(3)
45#define BCM2835_I2C_S_TXD	BIT(4)
46#define BCM2835_I2C_S_RXD	BIT(5)
47#define BCM2835_I2C_S_TXE	BIT(6)
48#define BCM2835_I2C_S_RXF	BIT(7)
49#define BCM2835_I2C_S_ERR	BIT(8)
50#define BCM2835_I2C_S_CLKT	BIT(9)
51#define BCM2835_I2C_S_LEN	BIT(10) /* Fake bit for SW error reporting */
52
53#define BCM2835_I2C_TIMEOUT (msecs_to_jiffies(1000))
54
55struct bcm2835_i2c_dev {
56	struct device *dev;
57	void __iomem *regs;
58	struct clk *clk;
59	int irq;
60	struct i2c_adapter adapter;
61	struct completion completion;
62	u32 msg_err;
63	u8 *msg_buf;
64	size_t msg_buf_remaining;
65};
66
67static inline void bcm2835_i2c_writel(struct bcm2835_i2c_dev *i2c_dev,
68				      u32 reg, u32 val)
69{
70	writel(val, i2c_dev->regs + reg);
71}
72
73static inline u32 bcm2835_i2c_readl(struct bcm2835_i2c_dev *i2c_dev, u32 reg)
74{
75	return readl(i2c_dev->regs + reg);
76}
77
78static void bcm2835_fill_txfifo(struct bcm2835_i2c_dev *i2c_dev)
79{
80	u32 val;
81
82	while (i2c_dev->msg_buf_remaining) {
83		val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
84		if (!(val & BCM2835_I2C_S_TXD))
85			break;
86		bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_FIFO,
87				   *i2c_dev->msg_buf);
88		i2c_dev->msg_buf++;
89		i2c_dev->msg_buf_remaining--;
90	}
91}
92
93static void bcm2835_drain_rxfifo(struct bcm2835_i2c_dev *i2c_dev)
94{
95	u32 val;
96
97	while (i2c_dev->msg_buf_remaining) {
98		val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
99		if (!(val & BCM2835_I2C_S_RXD))
100			break;
101		*i2c_dev->msg_buf = bcm2835_i2c_readl(i2c_dev,
102						      BCM2835_I2C_FIFO);
103		i2c_dev->msg_buf++;
104		i2c_dev->msg_buf_remaining--;
105	}
106}
107
108static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data)
109{
110	struct bcm2835_i2c_dev *i2c_dev = data;
111	u32 val, err;
112
113	val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
114	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_S, val);
115
116	err = val & (BCM2835_I2C_S_CLKT | BCM2835_I2C_S_ERR);
117	if (err) {
118		i2c_dev->msg_err = err;
119		complete(&i2c_dev->completion);
120		return IRQ_HANDLED;
121	}
122
123	if (val & BCM2835_I2C_S_RXD) {
124		bcm2835_drain_rxfifo(i2c_dev);
125		if (!(val & BCM2835_I2C_S_DONE))
126			return IRQ_HANDLED;
127	}
128
129	if (val & BCM2835_I2C_S_DONE) {
130		if (i2c_dev->msg_buf_remaining)
131			i2c_dev->msg_err = BCM2835_I2C_S_LEN;
132		else
133			i2c_dev->msg_err = 0;
134		complete(&i2c_dev->completion);
135		return IRQ_HANDLED;
136	}
137
138	if (val & BCM2835_I2C_S_TXD) {
139		bcm2835_fill_txfifo(i2c_dev);
140		return IRQ_HANDLED;
141	}
142
143	return IRQ_NONE;
144}
145
146static int bcm2835_i2c_xfer_msg(struct bcm2835_i2c_dev *i2c_dev,
147				struct i2c_msg *msg)
148{
149	u32 c;
150	unsigned long time_left;
151
152	i2c_dev->msg_buf = msg->buf;
153	i2c_dev->msg_buf_remaining = msg->len;
154	reinit_completion(&i2c_dev->completion);
155
156	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, BCM2835_I2C_C_CLEAR);
157
158	if (msg->flags & I2C_M_RD) {
159		c = BCM2835_I2C_C_READ | BCM2835_I2C_C_INTR;
160	} else {
161		c = BCM2835_I2C_C_INTT;
162		bcm2835_fill_txfifo(i2c_dev);
163	}
164	c |= BCM2835_I2C_C_ST | BCM2835_I2C_C_INTD | BCM2835_I2C_C_I2CEN;
165
166	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_A, msg->addr);
167	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DLEN, msg->len);
168	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, c);
169
170	time_left = wait_for_completion_timeout(&i2c_dev->completion,
171						BCM2835_I2C_TIMEOUT);
172	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, BCM2835_I2C_C_CLEAR);
173	if (!time_left) {
174		dev_err(i2c_dev->dev, "i2c transfer timed out\n");
175		return -ETIMEDOUT;
176	}
177
178	if (likely(!i2c_dev->msg_err))
179		return 0;
180
181	if ((i2c_dev->msg_err & BCM2835_I2C_S_ERR) &&
182	    (msg->flags & I2C_M_IGNORE_NAK))
183		return 0;
184
185	dev_err(i2c_dev->dev, "i2c transfer failed: %x\n", i2c_dev->msg_err);
186
187	if (i2c_dev->msg_err & BCM2835_I2C_S_ERR)
188		return -EREMOTEIO;
189	else
190		return -EIO;
191}
192
193static int bcm2835_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
194			    int num)
195{
196	struct bcm2835_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
197	int i;
198	int ret = 0;
199
200	for (i = 0; i < num; i++) {
201		ret = bcm2835_i2c_xfer_msg(i2c_dev, &msgs[i]);
202		if (ret)
203			break;
204	}
205
206	return ret ?: i;
207}
208
209static u32 bcm2835_i2c_func(struct i2c_adapter *adap)
210{
211	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
212}
213
214static const struct i2c_algorithm bcm2835_i2c_algo = {
215	.master_xfer	= bcm2835_i2c_xfer,
216	.functionality	= bcm2835_i2c_func,
217};
218
219static int bcm2835_i2c_probe(struct platform_device *pdev)
220{
221	struct bcm2835_i2c_dev *i2c_dev;
222	struct resource *mem, *irq;
223	u32 bus_clk_rate, divider;
224	int ret;
225	struct i2c_adapter *adap;
226
227	i2c_dev = devm_kzalloc(&pdev->dev, sizeof(*i2c_dev), GFP_KERNEL);
228	if (!i2c_dev)
229		return -ENOMEM;
230	platform_set_drvdata(pdev, i2c_dev);
231	i2c_dev->dev = &pdev->dev;
232	init_completion(&i2c_dev->completion);
233
234	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
235	i2c_dev->regs = devm_ioremap_resource(&pdev->dev, mem);
236	if (IS_ERR(i2c_dev->regs))
237		return PTR_ERR(i2c_dev->regs);
238
239	i2c_dev->clk = devm_clk_get(&pdev->dev, NULL);
240	if (IS_ERR(i2c_dev->clk)) {
241		dev_err(&pdev->dev, "Could not get clock\n");
242		return PTR_ERR(i2c_dev->clk);
243	}
244
245	ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency",
246				   &bus_clk_rate);
247	if (ret < 0) {
248		dev_warn(&pdev->dev,
249			 "Could not read clock-frequency property\n");
250		bus_clk_rate = 100000;
251	}
252
253	divider = DIV_ROUND_UP(clk_get_rate(i2c_dev->clk), bus_clk_rate);
254	/*
255	 * Per the datasheet, the register is always interpreted as an even
256	 * number, by rounding down. In other words, the LSB is ignored. So,
257	 * if the LSB is set, increment the divider to avoid any issue.
258	 */
259	if (divider & 1)
260		divider++;
261	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DIV, divider);
262
263	irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
264	if (!irq) {
265		dev_err(&pdev->dev, "No IRQ resource\n");
266		return -ENODEV;
267	}
268	i2c_dev->irq = irq->start;
269
270	ret = request_irq(i2c_dev->irq, bcm2835_i2c_isr, IRQF_SHARED,
271			  dev_name(&pdev->dev), i2c_dev);
272	if (ret) {
273		dev_err(&pdev->dev, "Could not request IRQ\n");
274		return -ENODEV;
275	}
276
277	adap = &i2c_dev->adapter;
278	i2c_set_adapdata(adap, i2c_dev);
279	adap->owner = THIS_MODULE;
280	adap->class = I2C_CLASS_DEPRECATED;
281	strlcpy(adap->name, "bcm2835 I2C adapter", sizeof(adap->name));
282	adap->algo = &bcm2835_i2c_algo;
283	adap->dev.parent = &pdev->dev;
284	adap->dev.of_node = pdev->dev.of_node;
285
286	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, 0);
287
288	ret = i2c_add_adapter(adap);
289	if (ret)
290		free_irq(i2c_dev->irq, i2c_dev);
291
292	return ret;
293}
294
295static int bcm2835_i2c_remove(struct platform_device *pdev)
296{
297	struct bcm2835_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
298
299	free_irq(i2c_dev->irq, i2c_dev);
300	i2c_del_adapter(&i2c_dev->adapter);
301
302	return 0;
303}
304
305static const struct of_device_id bcm2835_i2c_of_match[] = {
306	{ .compatible = "brcm,bcm2835-i2c" },
307	{},
308};
309MODULE_DEVICE_TABLE(of, bcm2835_i2c_of_match);
310
311static struct platform_driver bcm2835_i2c_driver = {
312	.probe		= bcm2835_i2c_probe,
313	.remove		= bcm2835_i2c_remove,
314	.driver		= {
315		.name	= "i2c-bcm2835",
316		.of_match_table = bcm2835_i2c_of_match,
317	},
318};
319module_platform_driver(bcm2835_i2c_driver);
320
321MODULE_AUTHOR("Stephen Warren <swarren@wwwdotorg.org>");
322MODULE_DESCRIPTION("BCM2835 I2C bus adapter");
323MODULE_LICENSE("GPL v2");
324MODULE_ALIAS("platform:i2c-bcm2835");
325