1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * I2C bus driver for Conexant Digicolor SoCs
4 *
5 * Author: Baruch Siach <baruch@tkos.co.il>
6 *
7 * Copyright (C) 2015 Paradox Innovation Ltd.
8 */
9
10 #include <linux/clk.h>
11 #include <linux/completion.h>
12 #include <linux/delay.h>
13 #include <linux/i2c.h>
14 #include <linux/interrupt.h>
15 #include <linux/io.h>
16 #include <linux/kernel.h>
17 #include <linux/module.h>
18 #include <linux/of.h>
19 #include <linux/platform_device.h>
20
21 #define TIMEOUT_MS 100
22
23 #define II_CONTROL 0x0
24 #define II_CONTROL_LOCAL_RESET BIT(0)
25
26 #define II_CLOCKTIME 0x1
27
28 #define II_COMMAND 0x2
29 #define II_CMD_START 1
30 #define II_CMD_RESTART 2
31 #define II_CMD_SEND_ACK 3
32 #define II_CMD_GET_ACK 6
33 #define II_CMD_GET_NOACK 7
34 #define II_CMD_STOP 10
35 #define II_COMMAND_GO BIT(7)
36 #define II_COMMAND_COMPLETION_STATUS(r) (((r) >> 5) & 3)
37 #define II_CMD_STATUS_NORMAL 0
38 #define II_CMD_STATUS_ACK_GOOD 1
39 #define II_CMD_STATUS_ACK_BAD 2
40 #define II_CMD_STATUS_ABORT 3
41
42 #define II_DATA 0x3
43 #define II_INTFLAG_CLEAR 0x8
44 #define II_INTENABLE 0xa
45
46 struct dc_i2c {
47 struct i2c_adapter adap;
48 struct device *dev;
49 void __iomem *regs;
50 struct clk *clk;
51 unsigned int frequency;
52
53 struct i2c_msg *msg;
54 unsigned int msgbuf_ptr;
55 int last;
56 spinlock_t lock;
57 struct completion done;
58 int state;
59 int error;
60 };
61
62 enum {
63 STATE_IDLE,
64 STATE_START,
65 STATE_ADDR,
66 STATE_WRITE,
67 STATE_READ,
68 STATE_STOP,
69 };
70
dc_i2c_cmd(struct dc_i2c * i2c,u8 cmd)71 static void dc_i2c_cmd(struct dc_i2c *i2c, u8 cmd)
72 {
73 writeb_relaxed(cmd | II_COMMAND_GO, i2c->regs + II_COMMAND);
74 }
75
dc_i2c_addr_cmd(struct i2c_msg * msg)76 static u8 dc_i2c_addr_cmd(struct i2c_msg *msg)
77 {
78 u8 addr = (msg->addr & 0x7f) << 1;
79
80 if (msg->flags & I2C_M_RD)
81 addr |= 1;
82
83 return addr;
84 }
85
dc_i2c_data(struct dc_i2c * i2c,u8 data)86 static void dc_i2c_data(struct dc_i2c *i2c, u8 data)
87 {
88 writeb_relaxed(data, i2c->regs + II_DATA);
89 }
90
dc_i2c_write_byte(struct dc_i2c * i2c,u8 byte)91 static void dc_i2c_write_byte(struct dc_i2c *i2c, u8 byte)
92 {
93 dc_i2c_data(i2c, byte);
94 dc_i2c_cmd(i2c, II_CMD_SEND_ACK);
95 }
96
dc_i2c_write_buf(struct dc_i2c * i2c)97 static void dc_i2c_write_buf(struct dc_i2c *i2c)
98 {
99 dc_i2c_write_byte(i2c, i2c->msg->buf[i2c->msgbuf_ptr++]);
100 }
101
dc_i2c_next_read(struct dc_i2c * i2c)102 static void dc_i2c_next_read(struct dc_i2c *i2c)
103 {
104 bool last = (i2c->msgbuf_ptr + 1 == i2c->msg->len);
105
106 dc_i2c_cmd(i2c, last ? II_CMD_GET_NOACK : II_CMD_GET_ACK);
107 }
108
dc_i2c_stop(struct dc_i2c * i2c)109 static void dc_i2c_stop(struct dc_i2c *i2c)
110 {
111 i2c->state = STATE_STOP;
112 if (i2c->last)
113 dc_i2c_cmd(i2c, II_CMD_STOP);
114 else
115 complete(&i2c->done);
116 }
117
dc_i2c_read_byte(struct dc_i2c * i2c)118 static u8 dc_i2c_read_byte(struct dc_i2c *i2c)
119 {
120 return readb_relaxed(i2c->regs + II_DATA);
121 }
122
dc_i2c_read_buf(struct dc_i2c * i2c)123 static void dc_i2c_read_buf(struct dc_i2c *i2c)
124 {
125 i2c->msg->buf[i2c->msgbuf_ptr++] = dc_i2c_read_byte(i2c);
126 dc_i2c_next_read(i2c);
127 }
128
dc_i2c_set_irq(struct dc_i2c * i2c,int enable)129 static void dc_i2c_set_irq(struct dc_i2c *i2c, int enable)
130 {
131 if (enable)
132 writeb_relaxed(1, i2c->regs + II_INTFLAG_CLEAR);
133 writeb_relaxed(!!enable, i2c->regs + II_INTENABLE);
134 }
135
dc_i2c_cmd_status(struct dc_i2c * i2c)136 static int dc_i2c_cmd_status(struct dc_i2c *i2c)
137 {
138 u8 cmd = readb_relaxed(i2c->regs + II_COMMAND);
139
140 return II_COMMAND_COMPLETION_STATUS(cmd);
141 }
142
dc_i2c_start_msg(struct dc_i2c * i2c,int first)143 static void dc_i2c_start_msg(struct dc_i2c *i2c, int first)
144 {
145 struct i2c_msg *msg = i2c->msg;
146
147 if (!(msg->flags & I2C_M_NOSTART)) {
148 i2c->state = STATE_START;
149 dc_i2c_cmd(i2c, first ? II_CMD_START : II_CMD_RESTART);
150 } else if (msg->flags & I2C_M_RD) {
151 i2c->state = STATE_READ;
152 dc_i2c_next_read(i2c);
153 } else {
154 i2c->state = STATE_WRITE;
155 dc_i2c_write_buf(i2c);
156 }
157 }
158
dc_i2c_irq(int irq,void * dev_id)159 static irqreturn_t dc_i2c_irq(int irq, void *dev_id)
160 {
161 struct dc_i2c *i2c = dev_id;
162 int cmd_status = dc_i2c_cmd_status(i2c);
163 u8 addr_cmd;
164
165 writeb_relaxed(1, i2c->regs + II_INTFLAG_CLEAR);
166
167 spin_lock(&i2c->lock);
168
169 if (cmd_status == II_CMD_STATUS_ACK_BAD
170 || cmd_status == II_CMD_STATUS_ABORT) {
171 i2c->error = -EIO;
172 complete(&i2c->done);
173 goto out;
174 }
175
176 switch (i2c->state) {
177 case STATE_START:
178 addr_cmd = dc_i2c_addr_cmd(i2c->msg);
179 dc_i2c_write_byte(i2c, addr_cmd);
180 i2c->state = STATE_ADDR;
181 break;
182 case STATE_ADDR:
183 if (i2c->msg->flags & I2C_M_RD) {
184 dc_i2c_next_read(i2c);
185 i2c->state = STATE_READ;
186 break;
187 }
188 i2c->state = STATE_WRITE;
189 fallthrough;
190 case STATE_WRITE:
191 if (i2c->msgbuf_ptr < i2c->msg->len)
192 dc_i2c_write_buf(i2c);
193 else
194 dc_i2c_stop(i2c);
195 break;
196 case STATE_READ:
197 if (i2c->msgbuf_ptr < i2c->msg->len)
198 dc_i2c_read_buf(i2c);
199 else
200 dc_i2c_stop(i2c);
201 break;
202 case STATE_STOP:
203 i2c->state = STATE_IDLE;
204 complete(&i2c->done);
205 break;
206 }
207
208 out:
209 spin_unlock(&i2c->lock);
210 return IRQ_HANDLED;
211 }
212
dc_i2c_xfer_msg(struct dc_i2c * i2c,struct i2c_msg * msg,int first,int last)213 static int dc_i2c_xfer_msg(struct dc_i2c *i2c, struct i2c_msg *msg, int first,
214 int last)
215 {
216 unsigned long timeout = msecs_to_jiffies(TIMEOUT_MS);
217 unsigned long flags;
218
219 spin_lock_irqsave(&i2c->lock, flags);
220 i2c->msg = msg;
221 i2c->msgbuf_ptr = 0;
222 i2c->last = last;
223 i2c->error = 0;
224
225 reinit_completion(&i2c->done);
226 dc_i2c_set_irq(i2c, 1);
227 dc_i2c_start_msg(i2c, first);
228 spin_unlock_irqrestore(&i2c->lock, flags);
229
230 timeout = wait_for_completion_timeout(&i2c->done, timeout);
231 dc_i2c_set_irq(i2c, 0);
232 if (timeout == 0) {
233 i2c->state = STATE_IDLE;
234 return -ETIMEDOUT;
235 }
236
237 if (i2c->error)
238 return i2c->error;
239
240 return 0;
241 }
242
dc_i2c_xfer(struct i2c_adapter * adap,struct i2c_msg * msgs,int num)243 static int dc_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
244 {
245 struct dc_i2c *i2c = adap->algo_data;
246 int i, ret;
247
248 for (i = 0; i < num; i++) {
249 ret = dc_i2c_xfer_msg(i2c, &msgs[i], i == 0, i == num - 1);
250 if (ret)
251 return ret;
252 }
253
254 return num;
255 }
256
dc_i2c_init_hw(struct dc_i2c * i2c)257 static int dc_i2c_init_hw(struct dc_i2c *i2c)
258 {
259 unsigned long clk_rate = clk_get_rate(i2c->clk);
260 unsigned int clocktime;
261
262 writeb_relaxed(II_CONTROL_LOCAL_RESET, i2c->regs + II_CONTROL);
263 udelay(100);
264 writeb_relaxed(0, i2c->regs + II_CONTROL);
265 udelay(100);
266
267 clocktime = DIV_ROUND_UP(clk_rate, 64 * i2c->frequency);
268 if (clocktime < 1 || clocktime > 0xff) {
269 dev_err(i2c->dev, "can't set bus speed of %u Hz\n",
270 i2c->frequency);
271 return -EINVAL;
272 }
273 writeb_relaxed(clocktime - 1, i2c->regs + II_CLOCKTIME);
274
275 return 0;
276 }
277
dc_i2c_func(struct i2c_adapter * adap)278 static u32 dc_i2c_func(struct i2c_adapter *adap)
279 {
280 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_NOSTART;
281 }
282
283 static const struct i2c_algorithm dc_i2c_algorithm = {
284 .master_xfer = dc_i2c_xfer,
285 .functionality = dc_i2c_func,
286 };
287
dc_i2c_probe(struct platform_device * pdev)288 static int dc_i2c_probe(struct platform_device *pdev)
289 {
290 struct device_node *np = pdev->dev.of_node;
291 struct dc_i2c *i2c;
292 int ret = 0, irq;
293
294 i2c = devm_kzalloc(&pdev->dev, sizeof(struct dc_i2c), GFP_KERNEL);
295 if (!i2c)
296 return -ENOMEM;
297
298 if (of_property_read_u32(pdev->dev.of_node, "clock-frequency",
299 &i2c->frequency))
300 i2c->frequency = I2C_MAX_STANDARD_MODE_FREQ;
301
302 i2c->dev = &pdev->dev;
303 platform_set_drvdata(pdev, i2c);
304
305 spin_lock_init(&i2c->lock);
306 init_completion(&i2c->done);
307
308 i2c->clk = devm_clk_get(&pdev->dev, NULL);
309 if (IS_ERR(i2c->clk))
310 return PTR_ERR(i2c->clk);
311
312 i2c->regs = devm_platform_ioremap_resource(pdev, 0);
313 if (IS_ERR(i2c->regs))
314 return PTR_ERR(i2c->regs);
315
316 irq = platform_get_irq(pdev, 0);
317 if (irq < 0)
318 return irq;
319
320 ret = devm_request_irq(&pdev->dev, irq, dc_i2c_irq, 0,
321 dev_name(&pdev->dev), i2c);
322 if (ret < 0)
323 return ret;
324
325 strscpy(i2c->adap.name, "Conexant Digicolor I2C adapter",
326 sizeof(i2c->adap.name));
327 i2c->adap.owner = THIS_MODULE;
328 i2c->adap.algo = &dc_i2c_algorithm;
329 i2c->adap.dev.parent = &pdev->dev;
330 i2c->adap.dev.of_node = np;
331 i2c->adap.algo_data = i2c;
332
333 ret = dc_i2c_init_hw(i2c);
334 if (ret)
335 return ret;
336
337 ret = clk_prepare_enable(i2c->clk);
338 if (ret < 0)
339 return ret;
340
341 ret = i2c_add_adapter(&i2c->adap);
342 if (ret < 0) {
343 clk_disable_unprepare(i2c->clk);
344 return ret;
345 }
346
347 return 0;
348 }
349
dc_i2c_remove(struct platform_device * pdev)350 static void dc_i2c_remove(struct platform_device *pdev)
351 {
352 struct dc_i2c *i2c = platform_get_drvdata(pdev);
353
354 i2c_del_adapter(&i2c->adap);
355 clk_disable_unprepare(i2c->clk);
356 }
357
358 static const struct of_device_id dc_i2c_match[] = {
359 { .compatible = "cnxt,cx92755-i2c" },
360 { },
361 };
362 MODULE_DEVICE_TABLE(of, dc_i2c_match);
363
364 static struct platform_driver dc_i2c_driver = {
365 .probe = dc_i2c_probe,
366 .remove_new = dc_i2c_remove,
367 .driver = {
368 .name = "digicolor-i2c",
369 .of_match_table = dc_i2c_match,
370 },
371 };
372 module_platform_driver(dc_i2c_driver);
373
374 MODULE_AUTHOR("Baruch Siach <baruch@tkos.co.il>");
375 MODULE_DESCRIPTION("Conexant Digicolor I2C master driver");
376 MODULE_LICENSE("GPL v2");
377