1 /*
2 i2c Support for Atmel's AT91 Two-Wire Interface (TWI)
3
4 Copyright (C) 2004 Rick Bronson
5 Converted to 2.6 by Andrew Victor <andrew@sanpeople.com>
6
7 Borrowed heavily from original work by:
8 Copyright (C) 2000 Philip Edelbrock <phil@stimpy.netroedge.com>
9
10 This program is free software; you can redistribute it and/or modify
11 it under the terms of the GNU General Public License as published by
12 the Free Software Foundation; either version 2 of the License, or
13 (at your option) any later version.
14 */
15
16 #include <linux/module.h>
17 #include <linux/kernel.h>
18 #include <linux/err.h>
19 #include <linux/slab.h>
20 #include <linux/types.h>
21 #include <linux/delay.h>
22 #include <linux/i2c.h>
23 #include <linux/init.h>
24 #include <linux/clk.h>
25 #include <linux/platform_device.h>
26
27 #include <asm/io.h>
28
29 #include <mach/at91_twi.h>
30 #include <mach/board.h>
31 #include <mach/cpu.h>
32
33 #define TWI_CLOCK 100000 /* Hz. max 400 Kbits/sec */
34
35
36 static struct clk *twi_clk;
37 static void __iomem *twi_base;
38
39 #define at91_twi_read(reg) __raw_readl(twi_base + (reg))
40 #define at91_twi_write(reg, val) __raw_writel((val), twi_base + (reg))
41
42
43 /*
44 * Initialize the TWI hardware registers.
45 */
at91_twi_hwinit(void)46 static void __devinit at91_twi_hwinit(void)
47 {
48 unsigned long cdiv, ckdiv;
49
50 at91_twi_write(AT91_TWI_IDR, 0xffffffff); /* Disable all interrupts */
51 at91_twi_write(AT91_TWI_CR, AT91_TWI_SWRST); /* Reset peripheral */
52 at91_twi_write(AT91_TWI_CR, AT91_TWI_MSEN); /* Set Master mode */
53
54 /* Calcuate clock dividers */
55 cdiv = (clk_get_rate(twi_clk) / (2 * TWI_CLOCK)) - 3;
56 cdiv = cdiv + 1; /* round up */
57 ckdiv = 0;
58 while (cdiv > 255) {
59 ckdiv++;
60 cdiv = cdiv >> 1;
61 }
62
63 if (cpu_is_at91rm9200()) { /* AT91RM9200 Errata #22 */
64 if (ckdiv > 5) {
65 printk(KERN_ERR "AT91 I2C: Invalid TWI_CLOCK value!\n");
66 ckdiv = 5;
67 }
68 }
69
70 at91_twi_write(AT91_TWI_CWGR, (ckdiv << 16) | (cdiv << 8) | cdiv);
71 }
72
73 /*
74 * Poll the i2c status register until the specified bit is set.
75 * Returns 0 if timed out (100 msec).
76 */
at91_poll_status(unsigned long bit)77 static short at91_poll_status(unsigned long bit)
78 {
79 int loop_cntr = 10000;
80
81 do {
82 udelay(10);
83 } while (!(at91_twi_read(AT91_TWI_SR) & bit) && (--loop_cntr > 0));
84
85 return (loop_cntr > 0);
86 }
87
xfer_read(struct i2c_adapter * adap,unsigned char * buf,int length)88 static int xfer_read(struct i2c_adapter *adap, unsigned char *buf, int length)
89 {
90 /* Send Start */
91 at91_twi_write(AT91_TWI_CR, AT91_TWI_START);
92
93 /* Read data */
94 while (length--) {
95 if (!length) /* need to send Stop before reading last byte */
96 at91_twi_write(AT91_TWI_CR, AT91_TWI_STOP);
97 if (!at91_poll_status(AT91_TWI_RXRDY)) {
98 dev_dbg(&adap->dev, "RXRDY timeout\n");
99 return -ETIMEDOUT;
100 }
101 *buf++ = (at91_twi_read(AT91_TWI_RHR) & 0xff);
102 }
103
104 return 0;
105 }
106
xfer_write(struct i2c_adapter * adap,unsigned char * buf,int length)107 static int xfer_write(struct i2c_adapter *adap, unsigned char *buf, int length)
108 {
109 /* Load first byte into transmitter */
110 at91_twi_write(AT91_TWI_THR, *buf++);
111
112 /* Send Start */
113 at91_twi_write(AT91_TWI_CR, AT91_TWI_START);
114
115 do {
116 if (!at91_poll_status(AT91_TWI_TXRDY)) {
117 dev_dbg(&adap->dev, "TXRDY timeout\n");
118 return -ETIMEDOUT;
119 }
120
121 length--; /* byte was transmitted */
122
123 if (length > 0) /* more data to send? */
124 at91_twi_write(AT91_TWI_THR, *buf++);
125 } while (length);
126
127 /* Send Stop */
128 at91_twi_write(AT91_TWI_CR, AT91_TWI_STOP);
129
130 return 0;
131 }
132
133 /*
134 * Generic i2c master transfer entrypoint.
135 *
136 * Note: We do not use Atmel's feature of storing the "internal device address".
137 * Instead the "internal device address" has to be written using a separate
138 * i2c message.
139 * http://lists.arm.linux.org.uk/pipermail/linux-arm-kernel/2004-September/024411.html
140 */
at91_xfer(struct i2c_adapter * adap,struct i2c_msg * pmsg,int num)141 static int at91_xfer(struct i2c_adapter *adap, struct i2c_msg *pmsg, int num)
142 {
143 int i, ret;
144
145 dev_dbg(&adap->dev, "at91_xfer: processing %d messages:\n", num);
146
147 for (i = 0; i < num; i++) {
148 dev_dbg(&adap->dev, " #%d: %sing %d byte%s %s 0x%02x\n", i,
149 pmsg->flags & I2C_M_RD ? "read" : "writ",
150 pmsg->len, pmsg->len > 1 ? "s" : "",
151 pmsg->flags & I2C_M_RD ? "from" : "to", pmsg->addr);
152
153 at91_twi_write(AT91_TWI_MMR, (pmsg->addr << 16)
154 | ((pmsg->flags & I2C_M_RD) ? AT91_TWI_MREAD : 0));
155
156 if (pmsg->len && pmsg->buf) { /* sanity check */
157 if (pmsg->flags & I2C_M_RD)
158 ret = xfer_read(adap, pmsg->buf, pmsg->len);
159 else
160 ret = xfer_write(adap, pmsg->buf, pmsg->len);
161
162 if (ret)
163 return ret;
164
165 /* Wait until transfer is finished */
166 if (!at91_poll_status(AT91_TWI_TXCOMP)) {
167 dev_dbg(&adap->dev, "TXCOMP timeout\n");
168 return -ETIMEDOUT;
169 }
170 }
171 dev_dbg(&adap->dev, "transfer complete\n");
172 pmsg++; /* next message */
173 }
174 return i;
175 }
176
177 /*
178 * Return list of supported functionality.
179 */
at91_func(struct i2c_adapter * adapter)180 static u32 at91_func(struct i2c_adapter *adapter)
181 {
182 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
183 }
184
185 static struct i2c_algorithm at91_algorithm = {
186 .master_xfer = at91_xfer,
187 .functionality = at91_func,
188 };
189
190 /*
191 * Main initialization routine.
192 */
at91_i2c_probe(struct platform_device * pdev)193 static int __devinit at91_i2c_probe(struct platform_device *pdev)
194 {
195 struct i2c_adapter *adapter;
196 struct resource *res;
197 int rc;
198
199 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
200 if (!res)
201 return -ENXIO;
202
203 if (!request_mem_region(res->start, res->end - res->start + 1, "at91_i2c"))
204 return -EBUSY;
205
206 twi_base = ioremap(res->start, res->end - res->start + 1);
207 if (!twi_base) {
208 rc = -ENOMEM;
209 goto fail0;
210 }
211
212 twi_clk = clk_get(NULL, "twi_clk");
213 if (IS_ERR(twi_clk)) {
214 dev_err(&pdev->dev, "no clock defined\n");
215 rc = -ENODEV;
216 goto fail1;
217 }
218
219 adapter = kzalloc(sizeof(struct i2c_adapter), GFP_KERNEL);
220 if (adapter == NULL) {
221 dev_err(&pdev->dev, "can't allocate inteface!\n");
222 rc = -ENOMEM;
223 goto fail2;
224 }
225 snprintf(adapter->name, sizeof(adapter->name), "AT91");
226 adapter->algo = &at91_algorithm;
227 adapter->class = I2C_CLASS_HWMON;
228 adapter->dev.parent = &pdev->dev;
229 /* adapter->id == 0 ... only one TWI controller for now */
230
231 platform_set_drvdata(pdev, adapter);
232
233 clk_enable(twi_clk); /* enable peripheral clock */
234 at91_twi_hwinit(); /* initialize TWI controller */
235
236 rc = i2c_add_numbered_adapter(adapter);
237 if (rc) {
238 dev_err(&pdev->dev, "Adapter %s registration failed\n",
239 adapter->name);
240 goto fail3;
241 }
242
243 dev_info(&pdev->dev, "AT91 i2c bus driver.\n");
244 return 0;
245
246 fail3:
247 platform_set_drvdata(pdev, NULL);
248 kfree(adapter);
249 clk_disable(twi_clk);
250 fail2:
251 clk_put(twi_clk);
252 fail1:
253 iounmap(twi_base);
254 fail0:
255 release_mem_region(res->start, res->end - res->start + 1);
256
257 return rc;
258 }
259
at91_i2c_remove(struct platform_device * pdev)260 static int __devexit at91_i2c_remove(struct platform_device *pdev)
261 {
262 struct i2c_adapter *adapter = platform_get_drvdata(pdev);
263 struct resource *res;
264 int rc;
265
266 rc = i2c_del_adapter(adapter);
267 platform_set_drvdata(pdev, NULL);
268
269 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
270 iounmap(twi_base);
271 release_mem_region(res->start, res->end - res->start + 1);
272
273 clk_disable(twi_clk); /* disable peripheral clock */
274 clk_put(twi_clk);
275
276 return rc;
277 }
278
279 #ifdef CONFIG_PM
280
281 /* NOTE: could save a few mA by keeping clock off outside of at91_xfer... */
282
at91_i2c_suspend(struct platform_device * pdev,pm_message_t mesg)283 static int at91_i2c_suspend(struct platform_device *pdev, pm_message_t mesg)
284 {
285 clk_disable(twi_clk);
286 return 0;
287 }
288
at91_i2c_resume(struct platform_device * pdev)289 static int at91_i2c_resume(struct platform_device *pdev)
290 {
291 return clk_enable(twi_clk);
292 }
293
294 #else
295 #define at91_i2c_suspend NULL
296 #define at91_i2c_resume NULL
297 #endif
298
299 /* work with "modprobe at91_i2c" from hotplugging or coldplugging */
300 MODULE_ALIAS("platform:at91_i2c");
301
302 static struct platform_driver at91_i2c_driver = {
303 .probe = at91_i2c_probe,
304 .remove = __devexit_p(at91_i2c_remove),
305 .suspend = at91_i2c_suspend,
306 .resume = at91_i2c_resume,
307 .driver = {
308 .name = "at91_i2c",
309 .owner = THIS_MODULE,
310 },
311 };
312
at91_i2c_init(void)313 static int __init at91_i2c_init(void)
314 {
315 return platform_driver_register(&at91_i2c_driver);
316 }
317
at91_i2c_exit(void)318 static void __exit at91_i2c_exit(void)
319 {
320 platform_driver_unregister(&at91_i2c_driver);
321 }
322
323 module_init(at91_i2c_init);
324 module_exit(at91_i2c_exit);
325
326 MODULE_AUTHOR("Rick Bronson");
327 MODULE_DESCRIPTION("I2C (TWI) driver for Atmel AT91");
328 MODULE_LICENSE("GPL");
329