aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/i2c/busses/i2c-at91.c
blob: c1adcdbf7979d5f958d9780a719c03c961171f84 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
/*
    i2c Support for Atmel's AT91 Two-Wire Interface (TWI)

    Copyright (C) 2004 Rick Bronson
    Converted to 2.6 by Andrew Victor <andrew@sanpeople.com>

    Borrowed heavily from original work by:
    Copyright (C) 2000 Philip Edelbrock <phil@stimpy.netroedge.com>

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.
*/

#include <linux/module.h>
#include <linux/version.h>
#include <linux/kernel.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/delay.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/clk.h>
#include <linux/platform_device.h>

#include <asm/io.h>

#include <mach/at91_twi.h>
#include <mach/board.h>
#include <mach/cpu.h>

#define TWI_CLOCK		100000		/* Hz. max 400 Kbits/sec */


static struct clk *twi_clk;
static void __iomem *twi_base;

#define at91_twi_read(reg)		__raw_readl(twi_base + (reg))
#define at91_twi_write(reg, val)	__raw_writel((val), twi_base + (reg))


/*
 * Initialize the TWI hardware registers.
 */
static void __devinit at91_twi_hwinit(void)
{
	unsigned long cdiv, ckdiv;

	at91_twi_write(AT91_TWI_IDR, 0xffffffff);	/* Disable all interrupts */
	at91_twi_write(AT91_TWI_CR, AT91_TWI_SWRST);	/* Reset peripheral */
	at91_twi_write(AT91_TWI_CR, AT91_TWI_MSEN);	/* Set Master mode */

	/* Calcuate clock dividers */
	cdiv = (clk_get_rate(twi_clk) / (2 * TWI_CLOCK)) - 3;
	cdiv = cdiv + 1;	/* round up */
	ckdiv = 0;
	while (cdiv > 255) {
		ckdiv++;
		cdiv = cdiv >> 1;
	}

	if (cpu_is_at91rm9200()) {			/* AT91RM9200 Errata #22 */
		if (ckdiv > 5) {
			printk(KERN_ERR "AT91 I2C: Invalid TWI_CLOCK value!\n");
			ckdiv = 5;
		}
	}

	at91_twi_write(AT91_TWI_CWGR, (ckdiv << 16) | (cdiv << 8) | cdiv);
}

/*
 * Poll the i2c status register until the specified bit is set.
 * Returns 0 if timed out (100 msec).
 */
static short at91_poll_status(unsigned long bit)
{
	int loop_cntr = 10000;

	do {
		udelay(10);
	} while (!(at91_twi_read(AT91_TWI_SR) & bit) && (--loop_cntr > 0));

	return (loop_cntr > 0);
}

static int xfer_read(struct i2c_adapter *adap, unsigned char *buf, int length)
{
	/* Send Start */
	at91_twi_write(AT91_TWI_CR, AT91_TWI_START);

	/* Read data */
	while (length--) {
		if (!length)	/* need to send Stop before reading last byte */
			at91_twi_write(AT91_TWI_CR, AT91_TWI_STOP);
		if (!at91_poll_status(AT91_TWI_RXRDY)) {
			dev_dbg(&adap->dev, "RXRDY timeout\n");
			return -ETIMEDOUT;
		}
		*buf++ = (at91_twi_read(AT91_TWI_RHR) & 0xff);
	}

	return 0;
}

static int xfer_write(struct i2c_adapter *adap, unsigned char *buf, int length)
{
	/* Load first byte into transmitter */
	at91_twi_write(AT91_TWI_THR, *buf++);

	/* Send Start */
	at91_twi_write(AT91_TWI_CR, AT91_TWI_START);

	do {
		if (!at91_poll_status(AT91_TWI_TXRDY)) {
			dev_dbg(&adap->dev, "TXRDY timeout\n");
			return -ETIMEDOUT;
		}

		length--;	/* byte was transmitted */

		if (length > 0)		/* more data to send? */
			at91_twi_write(AT91_TWI_THR, *buf++);
	} while (length);

	/* Send Stop */
	at91_twi_write(AT91_TWI_CR, AT91_TWI_STOP);

	return 0;
}

/*
 * Generic i2c master transfer entrypoint.
 *
 * Note: We do not use Atmel's feature of storing the "internal device address".
 * Instead the "internal device address" has to be written using a separate
 * i2c message.
 * http://lists.arm.linux.org.uk/pipermail/linux-arm-kernel/2004-September/024411.html
 */
static int at91_xfer(struct i2c_adapter *adap, struct i2c_msg *pmsg, int num)
{
	int i, ret;

	dev_dbg(&adap->dev, "at91_xfer: processing %d messages:\n", num);

	for (i = 0; i < num; i++) {
		dev_dbg(&adap->dev, " #%d: %sing %d byte%s %s 0x%02x\n", i,
			pmsg->flags & I2C_M_RD ? "read" : "writ",
			pmsg->len, pmsg->len > 1 ? "s" : "",
			pmsg->flags & I2C_M_RD ? "from" : "to",	pmsg->addr);

		at91_twi_write(AT91_TWI_MMR, (pmsg->addr << 16)
			| ((pmsg->flags & I2C_M_RD) ? AT91_TWI_MREAD : 0));

		if (pmsg->len && pmsg->buf) {	/* sanity check */
			if (pmsg->flags & I2C_M_RD)
				ret = xfer_read(adap, pmsg->buf, pmsg->len);
			else
				ret = xfer_write(adap, pmsg->buf, pmsg->len);

			if (ret)
				return ret;

			/* Wait until transfer is finished */
			if (!at91_poll_status(AT91_TWI_TXCOMP)) {
				dev_dbg(&adap->dev, "TXCOMP timeout\n");
				return -ETIMEDOUT;
			}
		}
		dev_dbg(&adap->dev, "transfer complete\n");
		pmsg++;		/* next message */
	}
	return i;
}

/*
 * Return list of supported functionality.
 */
static u32 at91_func(struct i2c_adapter *adapter)
{
	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
}

static struct i2c_algorithm at91_algorithm = {
	.master_xfer	= at91_xfer,
	.functionality	= at91_func,
};

/*
 * Main initialization routine.
 */
static int __devinit at91_i2c_probe(struct platform_device *pdev)
{
	struct i2c_adapter *adapter;
	struct resource *res;
	int rc;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (!res)
		return -ENXIO;

	if (!request_mem_region(res->start, res->end - res->start + 1, "at91_i2c"))
		return -EBUSY;

	twi_base = ioremap(res->start, res->end - res->start + 1);
	if (!twi_base) {
		rc = -ENOMEM;
		goto fail0;
	}

	twi_clk = clk_get(NULL, "twi_clk");
	if (IS_ERR(twi_clk)) {
		dev_err(&pdev->dev, "no clock defined\n");
		rc = -ENODEV;
		goto fail1;
	}

	adapter = kzalloc(sizeof(struct i2c_adapter), GFP_KERNEL);
	if (adapter == NULL) {
		dev_err(&pdev->dev, "can't allocate inteface!\n");
		rc = -ENOMEM;
		goto fail2;
	}
	sprintf(adapter->name, "AT91");
	adapter->algo = &at91_algorithm;
	adapter->class = I2C_CLASS_HWMON;
	adapter->dev.parent = &pdev->dev;
	/* adapter->id == 0 ... only one TWI controller for now */

	platform_set_drvdata(pdev, adapter);

	clk_enable(twi_clk);		/* enable peripheral clock */
	at91_twi_hwinit();		/* initialize TWI controller */

	rc = i2c_add_numbered_adapter(adapter);
	if (rc) {
		dev_err(&pdev->dev, "Adapter %s registration failed\n",
				adapter->name);
		goto fail3;
	}

	dev_info(&pdev->dev, "AT91 i2c bus driver.\n");
	return 0;

fail3:
	platform_set_drvdata(pdev, NULL);
	kfree(adapter);
	clk_disable(twi_clk);
fail2:
	clk_put(twi_clk);
fail1:
	iounmap(twi_base);
fail0:
	release_mem_region(res->start, res->end - res->start + 1);

	return rc;
}

static int __devexit at91_i2c_remove(struct platform_device *pdev)
{
	struct i2c_adapter *adapter = platform_get_drvdata(pdev);
	struct resource *res;
	int rc;

	rc = i2c_del_adapter(adapter);
	platform_set_drvdata(pdev, NULL);

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	iounmap(twi_base);
	release_mem_region(res->start, res->end - res->start + 1);

	clk_disable(twi_clk);		/* disable peripheral clock */
	clk_put(twi_clk);

	return rc;
}

#ifdef CONFIG_PM

/* NOTE: could save a few mA by keeping clock off outside of at91_xfer... */

static int at91_i2c_suspend(struct platform_device *pdev, pm_message_t mesg)
{
	clk_disable(twi_clk);
	return 0;
}

static int at91_i2c_resume(struct platform_device *pdev)
{
	return clk_enable(twi_clk);
}

#else
#define at91_i2c_suspend	NULL
#define at91_i2c_resume		NULL
#endif

/* work with "modprobe at91_i2c" from hotplugging or coldplugging */
MODULE_ALIAS("platform:at91_i2c");

static struct platform_driver at91_i2c_driver = {
	.probe		= at91_i2c_probe,
	.remove		= __devexit_p(at91_i2c_remove),
	.suspend	= at91_i2c_suspend,
	.resume		= at91_i2c_resume,
	.driver		= {
		.name	= "at91_i2c",
		.owner	= THIS_MODULE,
	},
};

static int __init at91_i2c_init(void)
{
	return platform_driver_register(&at91_i2c_driver);
}

static void __exit at91_i2c_exit(void)
{
	platform_driver_unregister(&at91_i2c_driver);
}

module_init(at91_i2c_init);
module_exit(at91_i2c_exit);

MODULE_AUTHOR("Rick Bronson");
MODULE_DESCRIPTION("I2C (TWI) driver for Atmel AT91");
MODULE_LICENSE("GPL");