summaryrefslogtreecommitdiffstats
path: root/drivers/i2c/busses/i2c-ibm_iic.c
blob: 1168d61418c95a86935729b007a03007dd28b371 (plain)
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
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
/*
 * drivers/i2c/busses/i2c-ibm_iic.c
 *
 * Support for the IIC peripheral on IBM PPC 4xx
 *
 * Copyright (c) 2003, 2004 Zultys Technologies.
 * Eugene Surovegin <eugene.surovegin@zultys.com> or <ebs@ebshome.net>
 *
 * Copyright (c) 2008 PIKA Technologies
 * Sean MacLennan <smaclennan@pikatech.com>
 *
 * Based on original work by
 * 	Ian DaSilva  <idasilva@mvista.com>
 *      Armin Kuster <akuster@mvista.com>
 * 	Matt Porter  <mporter@mvista.com>
 *
 *      Copyright 2000-2003 MontaVista Software Inc.
 *
 * Original driver version was highly leveraged from i2c-elektor.c
 *
 *   	Copyright 1995-97 Simon G. Vogl
 *                1998-99 Hans Berglund
 *
 *   	With some changes from Kyösti Mälkki <kmalkki@cc.hut.fi>
 *	and even Frodo Looijaard <frodol@dds.nl>
 *
 * 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/kernel.h>
#include <linux/ioport.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <asm/irq.h>
#include <linux/io.h>
#include <linux/i2c.h>
#include <linux/i2c-id.h>
#include <linux/of_platform.h>
#include <linux/of_i2c.h>

#include "i2c-ibm_iic.h"

#define DRIVER_VERSION "2.2"

MODULE_DESCRIPTION("IBM IIC driver v" DRIVER_VERSION);
MODULE_LICENSE("GPL");

static int iic_force_poll;
module_param(iic_force_poll, bool, 0);
MODULE_PARM_DESC(iic_force_poll, "Force polling mode");

static int iic_force_fast;
module_param(iic_force_fast, bool, 0);
MODULE_PARM_DESC(iic_force_fast, "Force fast mode (400 kHz)");

#define DBG_LEVEL 0

#ifdef DBG
#undef DBG
#endif

#ifdef DBG2
#undef DBG2
#endif

#if DBG_LEVEL > 0
#  define DBG(f,x...)	printk(KERN_DEBUG "ibm-iic" f, ##x)
#else
#  define DBG(f,x...)	((void)0)
#endif
#if DBG_LEVEL > 1
#  define DBG2(f,x...) 	DBG(f, ##x)
#else
#  define DBG2(f,x...) 	((void)0)
#endif
#if DBG_LEVEL > 2
static void dump_iic_regs(const char* header, struct ibm_iic_private* dev)
{
	volatile struct iic_regs __iomem *iic = dev->vaddr;
	printk(KERN_DEBUG "ibm-iic%d: %s\n", dev->idx, header);
	printk(KERN_DEBUG
	       "  cntl     = 0x%02x, mdcntl = 0x%02x\n"
	       "  sts      = 0x%02x, extsts = 0x%02x\n"
	       "  clkdiv   = 0x%02x, xfrcnt = 0x%02x\n"
	       "  xtcntlss = 0x%02x, directcntl = 0x%02x\n",
		in_8(&iic->cntl), in_8(&iic->mdcntl), in_8(&iic->sts),
		in_8(&iic->extsts), in_8(&iic->clkdiv), in_8(&iic->xfrcnt),
		in_8(&iic->xtcntlss), in_8(&iic->directcntl));
}
#  define DUMP_REGS(h,dev)	dump_iic_regs((h),(dev))
#else
#  define DUMP_REGS(h,dev)	((void)0)
#endif

/* Bus timings (in ns) for bit-banging */
static struct i2c_timings {
	unsigned int hd_sta;
	unsigned int su_sto;
	unsigned int low;
	unsigned int high;
	unsigned int buf;
} timings [] = {
/* Standard mode (100 KHz) */
{
	.hd_sta	= 4000,
	.su_sto	= 4000,
	.low	= 4700,
	.high	= 4000,
	.buf	= 4700,
},
/* Fast mode (400 KHz) */
{
	.hd_sta = 600,
	.su_sto	= 600,
	.low 	= 1300,
	.high 	= 600,
	.buf	= 1300,
}};

/* Enable/disable interrupt generation */
static inline void iic_interrupt_mode(struct ibm_iic_private* dev, int enable)
{
	out_8(&dev->vaddr->intmsk, enable ? INTRMSK_EIMTC : 0);
}

/*
 * Initialize IIC interface.
 */
static void iic_dev_init(struct ibm_iic_private* dev)
{
	volatile struct iic_regs __iomem *iic = dev->vaddr;

	DBG("%d: init\n", dev->idx);

	/* Clear master address */
	out_8(&iic->lmadr, 0);
	out_8(&iic->hmadr, 0);

	/* Clear slave address */
	out_8(&iic->lsadr, 0);
	out_8(&iic->hsadr, 0);

	/* Clear status & extended status */
	out_8(&iic->sts, STS_SCMP | STS_IRQA);
	out_8(&iic->extsts, EXTSTS_IRQP | EXTSTS_IRQD | EXTSTS_LA
			    | EXTSTS_ICT | EXTSTS_XFRA);

	/* Set clock divider */
	out_8(&iic->clkdiv, dev->clckdiv);

	/* Clear transfer count */
	out_8(&iic->xfrcnt, 0);

	/* Clear extended control and status */
	out_8(&iic->xtcntlss, XTCNTLSS_SRC | XTCNTLSS_SRS | XTCNTLSS_SWC
			    | XTCNTLSS_SWS);

	/* Clear control register */
	out_8(&iic->cntl, 0);

	/* Enable interrupts if possible */
	iic_interrupt_mode(dev, dev->irq >= 0);

	/* Set mode control */
	out_8(&iic->mdcntl, MDCNTL_FMDB | MDCNTL_EINT | MDCNTL_EUBS
			    | (dev->fast_mode ? MDCNTL_FSM : 0));

	DUMP_REGS("iic_init", dev);
}

/*
 * Reset IIC interface
 */
static void iic_dev_reset(struct ibm_iic_private* dev)
{
	volatile struct iic_regs __iomem *iic = dev->vaddr;
	int i;
	u8 dc;

	DBG("%d: soft reset\n", dev->idx);
	DUMP_REGS("reset", dev);

    	/* Place chip in the reset state */
	out_8(&iic->xtcntlss, XTCNTLSS_SRST);

	/* Check if bus is free */
	dc = in_8(&iic->directcntl);
	if (!DIRCTNL_FREE(dc)){
		DBG("%d: trying to regain bus control\n", dev->idx);

		/* Try to set bus free state */
		out_8(&iic->directcntl, DIRCNTL_SDAC | DIRCNTL_SCC);

		/* Wait until we regain bus control */
		for (i = 0; i < 100; ++i){
			dc = in_8(&iic->directcntl);
			if (DIRCTNL_FREE(dc))
				break;

			/* Toggle SCL line */
			dc ^= DIRCNTL_SCC;
			out_8(&iic->directcntl, dc);
			udelay(10);
			dc ^= DIRCNTL_SCC;
			out_8(&iic->directcntl, dc);

			/* be nice */
			cond_resched();
		}
	}

	/* Remove reset */
	out_8(&iic->xtcntlss, 0);

	/* Reinitialize interface */
	iic_dev_init(dev);
}

/*
 * Do 0-length transaction using bit-banging through IIC_DIRECTCNTL register.
 */

/* Wait for SCL and/or SDA to be high */
static int iic_dc_wait(volatile struct iic_regs __iomem *iic, u8 mask)
{
	unsigned long x = jiffies + HZ / 28 + 2;
	while ((in_8(&iic->directcntl) & mask) != mask){
		if (unlikely(time_after(jiffies, x)))
			return -1;
		cond_resched();
	}
	return 0;
}

static int iic_smbus_quick(struct ibm_iic_private* dev, const struct i2c_msg* p)
{
	volatile struct iic_regs __iomem *iic = dev->vaddr;
	const struct i2c_timings* t = &timings[dev->fast_mode ? 1 : 0];
	u8 mask, v, sda;
	int i, res;

	/* Only 7-bit addresses are supported */
	if (unlikely(p->flags & I2C_M_TEN)){
		DBG("%d: smbus_quick - 10 bit addresses are not supported\n",
			dev->idx);
		return -EINVAL;
	}

	DBG("%d: smbus_quick(0x%02x)\n", dev->idx, p->addr);

	/* Reset IIC interface */
	out_8(&iic->xtcntlss, XTCNTLSS_SRST);

	/* Wait for bus to become free */
	out_8(&iic->directcntl, DIRCNTL_SDAC | DIRCNTL_SCC);
	if (unlikely(iic_dc_wait(iic, DIRCNTL_MSDA | DIRCNTL_MSC)))
		goto err;
	ndelay(t->buf);

	/* START */
	out_8(&iic->directcntl, DIRCNTL_SCC);
	sda = 0;
	ndelay(t->hd_sta);

	/* Send address */
	v = (u8)((p->addr << 1) | ((p->flags & I2C_M_RD) ? 1 : 0));
	for (i = 0, mask = 0x80; i < 8; ++i, mask >>= 1){
		out_8(&iic->directcntl, sda);
		ndelay(t->low / 2);
		sda = (v & mask) ? DIRCNTL_SDAC : 0;
		out_8(&iic->directcntl, sda);
		ndelay(t->low / 2);

		out_8(&iic->directcntl, DIRCNTL_SCC | sda);
		if (unlikely(iic_dc_wait(iic, DIRCNTL_MSC)))
			goto err;
		ndelay(t->high);
	}

	/* ACK */
	out_8(&iic->directcntl, sda);
	ndelay(t->low / 2);
	out_8(&iic->directcntl, DIRCNTL_SDAC);
	ndelay(t->low / 2);
	out_8(&iic->directcntl, DIRCNTL_SDAC | DIRCNTL_SCC);
	if (unlikely(iic_dc_wait(iic, DIRCNTL_MSC)))
		goto err;
	res = (in_8(&iic->directcntl) & DIRCNTL_MSDA) ? -EREMOTEIO : 1;
	ndelay(t->high);

	/* STOP */
	out_8(&iic->directcntl, 0);
	ndelay(t->low);
	out_8(&iic->directcntl, DIRCNTL_SCC);
	if (unlikely(iic_dc_wait(iic, DIRCNTL_MSC)))
		goto err;
	ndelay(t->su_sto);
	out_8(&iic->directcntl, DIRCNTL_SDAC | DIRCNTL_SCC);

	ndelay(t->buf);

	DBG("%d: smbus_quick -> %s\n", dev->idx, res ? "NACK" : "ACK");
out:
	/* Remove reset */
	out_8(&iic->xtcntlss, 0);

	/* Reinitialize interface */
	iic_dev_init(dev);

	return res;
err:
	DBG("%d: smbus_quick - bus is stuck\n", dev->idx);
	res = -EREMOTEIO;
	goto out;
}

/*
 * IIC interrupt handler
 */
static irqreturn_t iic_handler(int irq, void *dev_id)
{
	struct ibm_iic_private* dev = (struct ibm_iic_private*)dev_id;
	volatile struct iic_regs __iomem *iic = dev->vaddr;

	DBG2("%d: irq handler, STS = 0x%02x, EXTSTS = 0x%02x\n",
	     dev->idx, in_8(&iic->sts), in_8(&iic->extsts));

	/* Acknowledge IRQ and wakeup iic_wait_for_tc */
	out_8(&iic->sts, STS_IRQA | STS_SCMP);
	wake_up_interruptible(&dev->wq);

	return IRQ_HANDLED;
}

/*
 * Get master transfer result and clear errors if any.
 * Returns the number of actually transferred bytes or error (<0)
 */
static int iic_xfer_result(struct ibm_iic_private* dev)
{
	volatile struct iic_regs __iomem *iic = dev->vaddr;

	if (unlikely(in_8(&iic->sts) & STS_ERR)){
		DBG("%d: xfer error, EXTSTS = 0x%02x\n", dev->idx,
			in_8(&iic->extsts));

		/* Clear errors and possible pending IRQs */
		out_8(&iic->extsts, EXTSTS_IRQP | EXTSTS_IRQD |
			EXTSTS_LA | EXTSTS_ICT | EXTSTS_XFRA);

		/* Flush master data buffer */
		out_8(&iic->mdcntl, in_8(&iic->mdcntl) | MDCNTL_FMDB);

		/* Is bus free?
		 * If error happened during combined xfer
		 * IIC interface is usually stuck in some strange
		 * state, the only way out - soft reset.
		 */
		if ((in_8(&iic->extsts) & EXTSTS_BCS_MASK) != EXTSTS_BCS_FREE){
			DBG("%d: bus is stuck, resetting\n", dev->idx);
			iic_dev_reset(dev);
		}
		return -EREMOTEIO;
	}
	else
		return in_8(&iic->xfrcnt) & XFRCNT_MTC_MASK;
}

/*
 * Try to abort active transfer.
 */
static void iic_abort_xfer(struct ibm_iic_private* dev)
{
	volatile struct iic_regs __iomem *iic = dev->vaddr;
	unsigned long x;

	DBG("%d: iic_abort_xfer\n", dev->idx);

	out_8(&iic->cntl, CNTL_HMT);

	/*
	 * Wait for the abort command to complete.
	 * It's not worth to be optimized, just poll (timeout >= 1 tick)
	 */
	x = jiffies + 2;
	while ((in_8(&iic->extsts) & EXTSTS_BCS_MASK) != EXTSTS_BCS_FREE){
		if (time_after(jiffies, x)){
			DBG("%d: abort timeout, resetting...\n", dev->idx);
			iic_dev_reset(dev);
			return;
		}
		schedule();
	}

	/* Just to clear errors */
	iic_xfer_result(dev);
}

/*
 * Wait for master transfer to complete.
 * It puts current process to sleep until we get interrupt or timeout expires.
 * Returns the number of transferred bytes or error (<0)
 */
static int iic_wait_for_tc(struct ibm_iic_private* dev){

	volatile struct iic_regs __iomem *iic = dev->vaddr;
	int ret = 0;

	if (dev->irq >= 0){
		/* Interrupt mode */
		ret = wait_event_interruptible_timeout(dev->wq,
			!(in_8(&iic->sts) & STS_PT), dev->adap.timeout);

		if (unlikely(ret < 0))
			DBG("%d: wait interrupted\n", dev->idx);
		else if (unlikely(in_8(&iic->sts) & STS_PT)){
			DBG("%d: wait timeout\n", dev->idx);
			ret = -ETIMEDOUT;
		}
	}
	else {
		/* Polling mode */
		unsigned long x = jiffies + dev->adap.timeout;

		while (in_8(&iic->sts) & STS_PT){
			if (unlikely(time_after(jiffies, x))){
				DBG("%d: poll timeout\n", dev->idx);
				ret = -ETIMEDOUT;
				break;
			}

			if (unlikely(signal_pending(current))){
				DBG("%d: poll interrupted\n", dev->idx);
				ret = -ERESTARTSYS;
				break;
			}
			schedule();
		}
	}

	if (unlikely(ret < 0))
		iic_abort_xfer(dev);
	else
		ret = iic_xfer_result(dev);

	DBG2("%d: iic_wait_for_tc -> %d\n", dev->idx, ret);

	return ret;
}

/*
 * Low level master transfer routine
 */
static int iic_xfer_bytes(struct ibm_iic_private* dev, struct i2c_msg* pm,
			  int combined_xfer)
{
	volatile struct iic_regs __iomem *iic = dev->vaddr;
	char* buf = pm->buf;
	int i, j, loops, ret = 0;
	int len = pm->len;

	u8 cntl = (in_8(&iic->cntl) & CNTL_AMD) | CNTL_PT;
	if (pm->flags & I2C_M_RD)
		cntl |= CNTL_RW;

	loops = (len + 3) / 4;
	for (i = 0; i < loops; ++i, len -= 4){
		int count = len > 4 ? 4 : len;
		u8 cmd = cntl | ((count - 1) << CNTL_TCT_SHIFT);

		if (!(cntl & CNTL_RW))
			for (j = 0; j < count; ++j)
				out_8((void __iomem *)&iic->mdbuf, *buf++);

		if (i < loops - 1)
			cmd |= CNTL_CHT;
		else if (combined_xfer)
			cmd |= CNTL_RPST;

		DBG2("%d: xfer_bytes, %d, CNTL = 0x%02x\n", dev->idx, count, cmd);

		/* Start transfer */
		out_8(&iic->cntl, cmd);

		/* Wait for completion */
		ret = iic_wait_for_tc(dev);

		if (unlikely(ret < 0))
			break;
		else if (unlikely(ret != count)){
			DBG("%d: xfer_bytes, requested %d, transfered %d\n",
				dev->idx, count, ret);

			/* If it's not a last part of xfer, abort it */
			if (combined_xfer || (i < loops - 1))
    				iic_abort_xfer(dev);

			ret = -EREMOTEIO;
			break;
		}

		if (cntl & CNTL_RW)
			for (j = 0; j < count; ++j)
				*buf++ = in_8((void __iomem *)&iic->mdbuf);
	}

	return ret > 0 ? 0 : ret;
}

/*
 * Set target slave address for master transfer
 */
static inline void iic_address(struct ibm_iic_private* dev, struct i2c_msg* msg)
{
	volatile struct iic_regs __iomem *iic = dev->vaddr;
	u16 addr = msg->addr;

	DBG2("%d: iic_address, 0x%03x (%d-bit)\n", dev->idx,
		addr, msg->flags & I2C_M_TEN ? 10 : 7);

	if (msg->flags & I2C_M_TEN){
	    out_8(&iic->cntl, CNTL_AMD);
	    out_8(&iic->lmadr, addr);
	    out_8(&iic->hmadr, 0xf0 | ((addr >> 7) & 0x06));
	}
	else {
	    out_8(&iic->cntl, 0);
	    out_8(&iic->lmadr, addr << 1);
	}
}

static inline int iic_invalid_address(const struct i2c_msg* p)
{
	return (p->addr > 0x3ff) || (!(p->flags & I2C_M_TEN) && (p->addr > 0x7f));
}

static inline int iic_address_neq(const struct i2c_msg* p1,
				  const struct i2c_msg* p2)
{
	return (p1->addr != p2->addr)
		|| ((p1->flags & I2C_M_TEN) != (p2->flags & I2C_M_TEN));
}

/*
 * Generic master transfer entrypoint.
 * Returns the number of processed messages or error (<0)
 */
static int iic_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
{
    	struct ibm_iic_private* dev = (struct ibm_iic_private*)(i2c_get_adapdata(adap));
	volatile struct iic_regs __iomem *iic = dev->vaddr;
	int i, ret = 0;

	DBG2("%d: iic_xfer, %d msg(s)\n", dev->idx, num);

	if (!num)
		return 0;

	/* Check the sanity of the passed messages.
	 * Uhh, generic i2c layer is more suitable place for such code...
	 */
	if (unlikely(iic_invalid_address(&msgs[0]))){
		DBG("%d: invalid address 0x%03x (%d-bit)\n", dev->idx,
			msgs[0].addr, msgs[0].flags & I2C_M_TEN ? 10 : 7);
		return -EINVAL;
	}
	for (i = 0; i < num; ++i){
		if (unlikely(msgs[i].len <= 0)){
			if (num == 1 && !msgs[0].len){
				/* Special case for I2C_SMBUS_QUICK emulation.
				 * IBM IIC doesn't support 0-length transactions
				 * so we have to emulate them using bit-banging.
				 */
				return iic_smbus_quick(dev, &msgs[0]);
			}
			DBG("%d: invalid len %d in msg[%d]\n", dev->idx,
				msgs[i].len, i);
			return -EINVAL;
		}
		if (unlikely(iic_address_neq(&msgs[0], &msgs[i]))){
			DBG("%d: invalid addr in msg[%d]\n", dev->idx, i);
			return -EINVAL;
		}
	}

	/* Check bus state */
	if (unlikely((in_8(&iic->extsts) & EXTSTS_BCS_MASK) != EXTSTS_BCS_FREE)){
		DBG("%d: iic_xfer, bus is not free\n", dev->idx);

		/* Usually it means something serious has happend.
		 * We *cannot* have unfinished previous transfer
		 * so it doesn't make any sense to try to stop it.
		 * Probably we were not able to recover from the
		 * previous error.
		 * The only *reasonable* thing I can think of here
		 * is soft reset.  --ebs
		 */
		iic_dev_reset(dev);

		if ((in_8(&iic->extsts) & EXTSTS_BCS_MASK) != EXTSTS_BCS_FREE){
			DBG("%d: iic_xfer, bus is still not free\n", dev->idx);
			return -EREMOTEIO;
		}
	}
	else {
		/* Flush master data buffer (just in case) */
		out_8(&iic->mdcntl, in_8(&iic->mdcntl) | MDCNTL_FMDB);
	}

	/* Load slave address */
	iic_address(dev, &msgs[0]);

	/* Do real transfer */
    	for (i = 0; i < num && !ret; ++i)
		ret = iic_xfer_bytes(dev, &msgs[i], i < num - 1);

	return ret < 0 ? ret : num;
}

static u32 iic_func(struct i2c_adapter *adap)
{
	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_10BIT_ADDR;
}

static const struct i2c_algorithm iic_algo = {
	.master_xfer 	= iic_xfer,
	.functionality	= iic_func
};

/*
 * Calculates IICx_CLCKDIV value for a specific OPB clock frequency
 */
static inline u8 iic_clckdiv(unsigned int opb)
{
	/* Compatibility kludge, should go away after all cards
	 * are fixed to fill correct value for opbfreq.
	 * Previous driver version used hardcoded divider value 4,
	 * it corresponds to OPB frequency from the range (40, 50] MHz
	 */
	if (!opb){
		printk(KERN_WARNING "ibm-iic: using compatibility value for OPB freq,"
			" fix your board specific setup\n");
		opb = 50000000;
	}

	/* Convert to MHz */
	opb /= 1000000;

	if (opb < 20 || opb > 150){
		printk(KERN_WARNING "ibm-iic: invalid OPB clock frequency %u MHz\n",
			opb);
		opb = opb < 20 ? 20 : 150;
	}
	return (u8)((opb + 9) / 10 - 1);
}

static int __devinit iic_request_irq(struct of_device *ofdev,
				     struct ibm_iic_private *dev)
{
	struct device_node *np = ofdev->dev.of_node;
	int irq;

	if (iic_force_poll)
		return 0;

	irq = irq_of_parse_and_map(np, 0);
	if (!irq) {
		dev_err(&ofdev->dev, "irq_of_parse_and_map failed\n");
		return 0;
	}

	/* Disable interrupts until we finish initialization, assumes
	 *  level-sensitive IRQ setup...
	 */
	iic_interrupt_mode(dev, 0);
	if (request_irq(irq, iic_handler, 0, "IBM IIC", dev)) {
		dev_err(&ofdev->dev, "request_irq %d failed\n", irq);
		/* Fallback to the polling mode */
		return 0;
	}

	return irq;
}

/*
 * Register single IIC interface
 */
static int __devinit iic_probe(struct of_device *ofdev,
			       const struct of_device_id *match)
{
	struct device_node *np = ofdev->dev.of_node;
	struct ibm_iic_private *dev;
	struct i2c_adapter *adap;
	const u32 *freq;
	int ret;

	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
	if (!dev) {
		dev_err(&ofdev->dev, "failed to allocate device data\n");
		return -ENOMEM;
	}

	dev_set_drvdata(&ofdev->dev, dev);

	dev->vaddr = of_iomap(np, 0);
	if (dev->vaddr == NULL) {
		dev_err(&ofdev->dev, "failed to iomap device\n");
		ret = -ENXIO;
		goto error_cleanup;
	}

	init_waitqueue_head(&dev->wq);

	dev->irq = iic_request_irq(ofdev, dev);
	if (!dev->irq)
		dev_warn(&ofdev->dev, "using polling mode\n");

	/* Board specific settings */
	if (iic_force_fast || of_get_property(np, "fast-mode", NULL))
		dev->fast_mode = 1;

	freq = of_get_property(np, "clock-frequency", NULL);
	if (freq == NULL) {
		freq = of_get_property(np->parent, "clock-frequency", NULL);
		if (freq == NULL) {
			dev_err(&ofdev->dev, "Unable to get bus frequency\n");
			ret = -EINVAL;
			goto error_cleanup;
		}
	}

	dev->clckdiv = iic_clckdiv(*freq);
	dev_dbg(&ofdev->dev, "clckdiv = %d\n", dev->clckdiv);

	/* Initialize IIC interface */
	iic_dev_init(dev);

	/* Register it with i2c layer */
	adap = &dev->adap;
	adap->dev.parent = &ofdev->dev;
	adap->dev.of_node = of_node_get(np);
	strlcpy(adap->name, "IBM IIC", sizeof(adap->name));
	i2c_set_adapdata(adap, dev);
	adap->class = I2C_CLASS_HWMON | I2C_CLASS_SPD;
	adap->algo = &iic_algo;
	adap->timeout = HZ;

	ret = i2c_add_adapter(adap);
	if (ret  < 0) {
		dev_err(&ofdev->dev, "failed to register i2c adapter\n");
		goto error_cleanup;
	}

	dev_info(&ofdev->dev, "using %s mode\n",
		 dev->fast_mode ? "fast (400 kHz)" : "standard (100 kHz)");

	return 0;

error_cleanup:
	if (dev->irq) {
		iic_interrupt_mode(dev, 0);
		free_irq(dev->irq, dev);
	}

	if (dev->vaddr)
		iounmap(dev->vaddr);

	dev_set_drvdata(&ofdev->dev, NULL);
	kfree(dev);
	return ret;
}

/*
 * Cleanup initialized IIC interface
 */
static int __devexit iic_remove(struct of_device *ofdev)
{
	struct ibm_iic_private *dev = dev_get_drvdata(&ofdev->dev);

	dev_set_drvdata(&ofdev->dev, NULL);

	i2c_del_adapter(&dev->adap);

	if (dev->irq) {
		iic_interrupt_mode(dev, 0);
		free_irq(dev->irq, dev);
	}

	iounmap(dev->vaddr);
	kfree(dev);

	return 0;
}

static const struct of_device_id ibm_iic_match[] = {
	{ .compatible = "ibm,iic", },
	{}
};

static struct of_platform_driver ibm_iic_driver = {
	.driver = {
		.name = "ibm-iic",
		.owner = THIS_MODULE,
		.of_match_table = ibm_iic_match,
	},
	.probe	= iic_probe,
	.remove	= __devexit_p(iic_remove),
};

static int __init iic_init(void)
{
	return of_register_platform_driver(&ibm_iic_driver);
}

static void __exit iic_exit(void)
{
	of_unregister_platform_driver(&ibm_iic_driver);
}

module_init(iic_init);
module_exit(iic_exit);