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 <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;
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
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
300/* work with "modprobe at91_i2c" from hotplugging or coldplugging */
301MODULE_ALIAS("at91_i2c");
302
303static 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");
330