Merge branch 'linus' into x86/doc
[linux-2.6] / drivers / i2c / busses / i2c-at91.c
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/version.h>
18 #include <linux/kernel.h>
19 #include <linux/err.h>
20 #include <linux/slab.h>
21 #include <linux/types.h>
22 #include <linux/delay.h>
23 #include <linux/i2c.h>
24 #include <linux/init.h>
25 #include <linux/clk.h>
26 #include <linux/platform_device.h>
27
28 #include <asm/io.h>
29
30 #include <mach/at91_twi.h>
31 #include <mach/board.h>
32 #include <mach/cpu.h>
33
34 #define TWI_CLOCK               100000          /* Hz. max 400 Kbits/sec */
35
36
37 static struct clk *twi_clk;
38 static void __iomem *twi_base;
39
40 #define at91_twi_read(reg)              __raw_readl(twi_base + (reg))
41 #define at91_twi_write(reg, val)        __raw_writel((val), twi_base + (reg))
42
43
44 /*
45  * Initialize the TWI hardware registers.
46  */
47 static void __devinit at91_twi_hwinit(void)
48 {
49         unsigned long cdiv, ckdiv;
50
51         at91_twi_write(AT91_TWI_IDR, 0xffffffff);       /* Disable all interrupts */
52         at91_twi_write(AT91_TWI_CR, AT91_TWI_SWRST);    /* Reset peripheral */
53         at91_twi_write(AT91_TWI_CR, AT91_TWI_MSEN);     /* Set Master mode */
54
55         /* Calcuate clock dividers */
56         cdiv = (clk_get_rate(twi_clk) / (2 * TWI_CLOCK)) - 3;
57         cdiv = cdiv + 1;        /* round up */
58         ckdiv = 0;
59         while (cdiv > 255) {
60                 ckdiv++;
61                 cdiv = cdiv >> 1;
62         }
63
64         if (cpu_is_at91rm9200()) {                      /* AT91RM9200 Errata #22 */
65                 if (ckdiv > 5) {
66                         printk(KERN_ERR "AT91 I2C: Invalid TWI_CLOCK value!\n");
67                         ckdiv = 5;
68                 }
69         }
70
71         at91_twi_write(AT91_TWI_CWGR, (ckdiv << 16) | (cdiv << 8) | cdiv);
72 }
73
74 /*
75  * Poll the i2c status register until the specified bit is set.
76  * Returns 0 if timed out (100 msec).
77  */
78 static short at91_poll_status(unsigned long bit)
79 {
80         int loop_cntr = 10000;
81
82         do {
83                 udelay(10);
84         } while (!(at91_twi_read(AT91_TWI_SR) & bit) && (--loop_cntr > 0));
85
86         return (loop_cntr > 0);
87 }
88
89 static int xfer_read(struct i2c_adapter *adap, unsigned char *buf, int length)
90 {
91         /* Send Start */
92         at91_twi_write(AT91_TWI_CR, AT91_TWI_START);
93
94         /* Read data */
95         while (length--) {
96                 if (!length)    /* need to send Stop before reading last byte */
97                         at91_twi_write(AT91_TWI_CR, AT91_TWI_STOP);
98                 if (!at91_poll_status(AT91_TWI_RXRDY)) {
99                         dev_dbg(&adap->dev, "RXRDY timeout\n");
100                         return -ETIMEDOUT;
101                 }
102                 *buf++ = (at91_twi_read(AT91_TWI_RHR) & 0xff);
103         }
104
105         return 0;
106 }
107
108 static int xfer_write(struct i2c_adapter *adap, unsigned char *buf, int length)
109 {
110         /* Load first byte into transmitter */
111         at91_twi_write(AT91_TWI_THR, *buf++);
112
113         /* Send Start */
114         at91_twi_write(AT91_TWI_CR, AT91_TWI_START);
115
116         do {
117                 if (!at91_poll_status(AT91_TWI_TXRDY)) {
118                         dev_dbg(&adap->dev, "TXRDY timeout\n");
119                         return -ETIMEDOUT;
120                 }
121
122                 length--;       /* byte was transmitted */
123
124                 if (length > 0)         /* more data to send? */
125                         at91_twi_write(AT91_TWI_THR, *buf++);
126         } while (length);
127
128         /* Send Stop */
129         at91_twi_write(AT91_TWI_CR, AT91_TWI_STOP);
130
131         return 0;
132 }
133
134 /*
135  * Generic i2c master transfer entrypoint.
136  *
137  * Note: We do not use Atmel's feature of storing the "internal device address".
138  * Instead the "internal device address" has to be written using a separate
139  * i2c message.
140  * http://lists.arm.linux.org.uk/pipermail/linux-arm-kernel/2004-September/024411.html
141  */
142 static int at91_xfer(struct i2c_adapter *adap, struct i2c_msg *pmsg, int num)
143 {
144         int i, ret;
145
146         dev_dbg(&adap->dev, "at91_xfer: processing %d messages:\n", num);
147
148         for (i = 0; i < num; i++) {
149                 dev_dbg(&adap->dev, " #%d: %sing %d byte%s %s 0x%02x\n", i,
150                         pmsg->flags & I2C_M_RD ? "read" : "writ",
151                         pmsg->len, pmsg->len > 1 ? "s" : "",
152                         pmsg->flags & I2C_M_RD ? "from" : "to", pmsg->addr);
153
154                 at91_twi_write(AT91_TWI_MMR, (pmsg->addr << 16)
155                         | ((pmsg->flags & I2C_M_RD) ? AT91_TWI_MREAD : 0));
156
157                 if (pmsg->len && pmsg->buf) {   /* sanity check */
158                         if (pmsg->flags & I2C_M_RD)
159                                 ret = xfer_read(adap, pmsg->buf, pmsg->len);
160                         else
161                                 ret = xfer_write(adap, pmsg->buf, pmsg->len);
162
163                         if (ret)
164                                 return ret;
165
166                         /* Wait until transfer is finished */
167                         if (!at91_poll_status(AT91_TWI_TXCOMP)) {
168                                 dev_dbg(&adap->dev, "TXCOMP timeout\n");
169                                 return -ETIMEDOUT;
170                         }
171                 }
172                 dev_dbg(&adap->dev, "transfer complete\n");
173                 pmsg++;         /* next message */
174         }
175         return i;
176 }
177
178 /*
179  * Return list of supported functionality.
180  */
181 static u32 at91_func(struct i2c_adapter *adapter)
182 {
183         return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
184 }
185
186 static struct i2c_algorithm at91_algorithm = {
187         .master_xfer    = at91_xfer,
188         .functionality  = at91_func,
189 };
190
191 /*
192  * Main initialization routine.
193  */
194 static int __devinit at91_i2c_probe(struct platform_device *pdev)
195 {
196         struct i2c_adapter *adapter;
197         struct resource *res;
198         int rc;
199
200         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
201         if (!res)
202                 return -ENXIO;
203
204         if (!request_mem_region(res->start, res->end - res->start + 1, "at91_i2c"))
205                 return -EBUSY;
206
207         twi_base = ioremap(res->start, res->end - res->start + 1);
208         if (!twi_base) {
209                 rc = -ENOMEM;
210                 goto fail0;
211         }
212
213         twi_clk = clk_get(NULL, "twi_clk");
214         if (IS_ERR(twi_clk)) {
215                 dev_err(&pdev->dev, "no clock defined\n");
216                 rc = -ENODEV;
217                 goto fail1;
218         }
219
220         adapter = kzalloc(sizeof(struct i2c_adapter), GFP_KERNEL);
221         if (adapter == NULL) {
222                 dev_err(&pdev->dev, "can't allocate inteface!\n");
223                 rc = -ENOMEM;
224                 goto fail2;
225         }
226         sprintf(adapter->name, "AT91");
227         adapter->algo = &at91_algorithm;
228         adapter->class = I2C_CLASS_HWMON;
229         adapter->dev.parent = &pdev->dev;
230         /* adapter->id == 0 ... only one TWI controller for now */
231
232         platform_set_drvdata(pdev, adapter);
233
234         clk_enable(twi_clk);            /* enable peripheral clock */
235         at91_twi_hwinit();              /* initialize TWI controller */
236
237         rc = i2c_add_numbered_adapter(adapter);
238         if (rc) {
239                 dev_err(&pdev->dev, "Adapter %s registration failed\n",
240                                 adapter->name);
241                 goto fail3;
242         }
243
244         dev_info(&pdev->dev, "AT91 i2c bus driver.\n");
245         return 0;
246
247 fail3:
248         platform_set_drvdata(pdev, NULL);
249         kfree(adapter);
250         clk_disable(twi_clk);
251 fail2:
252         clk_put(twi_clk);
253 fail1:
254         iounmap(twi_base);
255 fail0:
256         release_mem_region(res->start, res->end - res->start + 1);
257
258         return rc;
259 }
260
261 static int __devexit at91_i2c_remove(struct platform_device *pdev)
262 {
263         struct i2c_adapter *adapter = platform_get_drvdata(pdev);
264         struct resource *res;
265         int rc;
266
267         rc = i2c_del_adapter(adapter);
268         platform_set_drvdata(pdev, NULL);
269
270         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
271         iounmap(twi_base);
272         release_mem_region(res->start, res->end - res->start + 1);
273
274         clk_disable(twi_clk);           /* disable peripheral clock */
275         clk_put(twi_clk);
276
277         return rc;
278 }
279
280 #ifdef CONFIG_PM
281
282 /* NOTE: could save a few mA by keeping clock off outside of at91_xfer... */
283
284 static int at91_i2c_suspend(struct platform_device *pdev, pm_message_t mesg)
285 {
286         clk_disable(twi_clk);
287         return 0;
288 }
289
290 static int at91_i2c_resume(struct platform_device *pdev)
291 {
292         return clk_enable(twi_clk);
293 }
294
295 #else
296 #define at91_i2c_suspend        NULL
297 #define at91_i2c_resume         NULL
298 #endif
299
300 /* work with "modprobe at91_i2c" from hotplugging or coldplugging */
301 MODULE_ALIAS("platform:at91_i2c");
302
303 static struct platform_driver at91_i2c_driver = {
304         .probe          = at91_i2c_probe,
305         .remove         = __devexit_p(at91_i2c_remove),
306         .suspend        = at91_i2c_suspend,
307         .resume         = at91_i2c_resume,
308         .driver         = {
309                 .name   = "at91_i2c",
310                 .owner  = THIS_MODULE,
311         },
312 };
313
314 static int __init at91_i2c_init(void)
315 {
316         return platform_driver_register(&at91_i2c_driver);
317 }
318
319 static void __exit at91_i2c_exit(void)
320 {
321         platform_driver_unregister(&at91_i2c_driver);
322 }
323
324 module_init(at91_i2c_init);
325 module_exit(at91_i2c_exit);
326
327 MODULE_AUTHOR("Rick Bronson");
328 MODULE_DESCRIPTION("I2C (TWI) driver for Atmel AT91");
329 MODULE_LICENSE("GPL");