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Andrew Victor813e30e2006-12-10 21:21:30 +01001/*
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>
Alexey Dobriyanc91e23c2007-05-10 03:15:58 -070019#include <linux/err.h>
Andrew Victor813e30e2006-12-10 21:21:30 +010020#include <linux/slab.h>
Andrew Victor813e30e2006-12-10 21:21:30 +010021#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 <asm/arch/at91_twi.h>
31#include <asm/arch/board.h>
32#include <asm/arch/cpu.h>
33
34#define TWI_CLOCK 100000 /* Hz. max 400 Kbits/sec */
35
36
37static struct clk *twi_clk;
38static 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 */
47static 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 */
78static 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
89static 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
108static 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 seperate
139 * i2c message.
140 * http://lists.arm.linux.org.uk/pipermail/linux-arm-kernel/2004-September/024411.html
141 */
142static 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 */
181static u32 at91_func(struct i2c_adapter *adapter)
182{
183 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
184}
185
186static struct i2c_algorithm at91_algorithm = {
187 .master_xfer = at91_xfer,
188 .functionality = at91_func,
189};
190
191/*
192 * Main initialization routine.
193 */
194static 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;
David Brownell6e998062007-05-10 03:15:52 -0700230 /* adapter->id == 0 ... only one TWI controller for now */
Andrew Victor813e30e2006-12-10 21:21:30 +0100231
232 platform_set_drvdata(pdev, adapter);
233
234 clk_enable(twi_clk); /* enable peripheral clock */
235 at91_twi_hwinit(); /* initialize TWI controller */
236
David Brownell6e998062007-05-10 03:15:52 -0700237 rc = i2c_add_numbered_adapter(adapter);
Andrew Victor813e30e2006-12-10 21:21:30 +0100238 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
247fail3:
248 platform_set_drvdata(pdev, NULL);
249 kfree(adapter);
250 clk_disable(twi_clk);
251fail2:
252 clk_put(twi_clk);
253fail1:
254 iounmap(twi_base);
255fail0:
256 release_mem_region(res->start, res->end - res->start + 1);
257
258 return rc;
259}
260
261static 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
284static int at91_i2c_suspend(struct platform_device *pdev, pm_message_t mesg)
285{
286 clk_disable(twi_clk);
287 return 0;
288}
289
290static 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
David Brownell6e998062007-05-10 03:15:52 -0700300/* work with "modprobe at91_i2c" from hotplugging or coldplugging */
301MODULE_ALIAS("at91_i2c");
302
Andrew Victor813e30e2006-12-10 21:21:30 +0100303static 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
314static int __init at91_i2c_init(void)
315{
316 return platform_driver_register(&at91_i2c_driver);
317}
318
319static void __exit at91_i2c_exit(void)
320{
321 platform_driver_unregister(&at91_i2c_driver);
322}
323
324module_init(at91_i2c_init);
325module_exit(at91_i2c_exit);
326
327MODULE_AUTHOR("Rick Bronson");
328MODULE_DESCRIPTION("I2C (TWI) driver for Atmel AT91");
329MODULE_LICENSE("GPL");