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