summaryrefslogtreecommitdiff
path: root/drivers/staging/omapdrm/tcm-sita.c
blob: 10d5ac3dae4bde78f52da0ce75f1e8bf3ab2b8ba (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
/*
 * tcm-sita.c
 *
 * SImple Tiler Allocator (SiTA): 2D and 1D allocation(reservation) algorithm
 *
 * Authors: Ravi Ramachandra <r.ramachandra@ti.com>,
 *          Lajos Molnar <molnar@ti.com>
 *
 * Copyright (C) 2009-2010 Texas Instruments, Inc.
 *
 * This package is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * THIS PACKAGE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 */
#include <linux/slab.h>
#include <linux/spinlock.h>

#include "tcm-sita.h"

#define ALIGN_DOWN(value, align) ((value) & ~((align) - 1))

/* Individual selection criteria for different scan areas */
static s32 CR_L2R_T2B = CR_BIAS_HORIZONTAL;
static s32 CR_R2L_T2B = CR_DIAGONAL_BALANCE;

/*********************************************
 *	TCM API - Sita Implementation
 *********************************************/
static s32 sita_reserve_2d(struct tcm *tcm, u16 h, u16 w, u8 align,
			   struct tcm_area *area);
static s32 sita_reserve_1d(struct tcm *tcm, u32 slots, struct tcm_area *area);
static s32 sita_free(struct tcm *tcm, struct tcm_area *area);
static void sita_deinit(struct tcm *tcm);

/*********************************************
 *	Main Scanner functions
 *********************************************/
static s32 scan_areas_and_find_fit(struct tcm *tcm, u16 w, u16 h, u16 align,
				   struct tcm_area *area);

static s32 scan_l2r_t2b(struct tcm *tcm, u16 w, u16 h, u16 align,
			struct tcm_area *field, struct tcm_area *area);

static s32 scan_r2l_t2b(struct tcm *tcm, u16 w, u16 h, u16 align,
			struct tcm_area *field, struct tcm_area *area);

static s32 scan_r2l_b2t_one_dim(struct tcm *tcm, u32 num_slots,
			struct tcm_area *field, struct tcm_area *area);

/*********************************************
 *	Support Infrastructure Methods
 *********************************************/
static s32 is_area_free(struct tcm_area ***map, u16 x0, u16 y0, u16 w, u16 h);

static s32 update_candidate(struct tcm *tcm, u16 x0, u16 y0, u16 w, u16 h,
			    struct tcm_area *field, s32 criteria,
			    struct score *best);

static void get_nearness_factor(struct tcm_area *field,
				struct tcm_area *candidate,
				struct nearness_factor *nf);

static void get_neighbor_stats(struct tcm *tcm, struct tcm_area *area,
			       struct neighbor_stats *stat);

static void fill_area(struct tcm *tcm,
				struct tcm_area *area, struct tcm_area *parent);


/*********************************************/

/*********************************************
 *	Utility Methods
 *********************************************/
struct tcm *sita_init(u16 width, u16 height, struct tcm_pt *attr)
{
	struct tcm *tcm;
	struct sita_pvt *pvt;
	struct tcm_area area = {0};
	s32 i;

	if (width == 0 || height == 0)
		return NULL;

	tcm = kmalloc(sizeof(*tcm), GFP_KERNEL);
	pvt = kmalloc(sizeof(*pvt), GFP_KERNEL);
	if (!tcm || !pvt)
		goto error;

	memset(tcm, 0, sizeof(*tcm));
	memset(pvt, 0, sizeof(*pvt));

	/* Updating the pointers to SiTA implementation APIs */
	tcm->height = height;
	tcm->width = width;
	tcm->reserve_2d = sita_reserve_2d;
	tcm->reserve_1d = sita_reserve_1d;
	tcm->free = sita_free;
	tcm->deinit = sita_deinit;
	tcm->pvt = (void *)pvt;

	spin_lock_init(&(pvt->lock));

	/* Creating tam map */
	pvt->map = kmalloc(sizeof(*pvt->map) * tcm->width, GFP_KERNEL);
	if (!pvt->map)
		goto error;

	for (i = 0; i < tcm->width; i++) {
		pvt->map[i] =
			kmalloc(sizeof(**pvt->map) * tcm->height,
								GFP_KERNEL);
		if (pvt->map[i] == NULL) {
			while (i--)
				kfree(pvt->map[i]);
			kfree(pvt->map);
			goto error;
		}
	}

	if (attr && attr->x <= tcm->width && attr->y <= tcm->height) {
		pvt->div_pt.x = attr->x;
		pvt->div_pt.y = attr->y;

	} else {
		/* Defaulting to 3:1 ratio on width for 2D area split */
		/* Defaulting to 3:1 ratio on height for 2D and 1D split */
		pvt->div_pt.x = (tcm->width * 3) / 4;
		pvt->div_pt.y = (tcm->height * 3) / 4;
	}

	spin_lock(&(pvt->lock));
	assign(&area, 0, 0, width - 1, height - 1);
	fill_area(tcm, &area, NULL);
	spin_unlock(&(pvt->lock));
	return tcm;

error:
	kfree(tcm);
	kfree(pvt);
	return NULL;
}

static void sita_deinit(struct tcm *tcm)
{
	struct sita_pvt *pvt = (struct sita_pvt *)tcm->pvt;
	struct tcm_area area = {0};
	s32 i;

	area.p1.x = tcm->width - 1;
	area.p1.y = tcm->height - 1;

	spin_lock(&(pvt->lock));
	fill_area(tcm, &area, NULL);
	spin_unlock(&(pvt->lock));

	for (i = 0; i < tcm->height; i++)
		kfree(pvt->map[i]);
	kfree(pvt->map);
	kfree(pvt);
}

/**
 * Reserve a 1D area in the container
 *
 * @param num_slots	size of 1D area
 * @param area		pointer to the area that will be populated with the
 *			reserved area
 *
 * @return 0 on success, non-0 error value on failure.
 */
static s32 sita_reserve_1d(struct tcm *tcm, u32 num_slots,
			   struct tcm_area *area)
{
	s32 ret;
	struct tcm_area field = {0};
	struct sita_pvt *pvt = (struct sita_pvt *)tcm->pvt;

	spin_lock(&(pvt->lock));

	/* Scanning entire container */
	assign(&field, tcm->width - 1, tcm->height - 1, 0, 0);

	ret = scan_r2l_b2t_one_dim(tcm, num_slots, &field, area);
	if (!ret)
		/* update map */
		fill_area(tcm, area, area);

	spin_unlock(&(pvt->lock));
	return ret;
}

/**
 * Reserve a 2D area in the container
 *
 * @param w	width
 * @param h	height
 * @param area	pointer to the area that will be populated with the reesrved
 *		area
 *
 * @return 0 on success, non-0 error value on failure.
 */
static s32 sita_reserve_2d(struct tcm *tcm, u16 h, u16 w, u8 align,
			   struct tcm_area *area)
{
	s32 ret;
	struct sita_pvt *pvt = (struct sita_pvt *)tcm->pvt;

	/* not supporting more than 64 as alignment */
	if (align > 64)
		return -EINVAL;

	/* we prefer 1, 32 and 64 as alignment */
	align = align <= 1 ? 1 : align <= 32 ? 32 : 64;

	spin_lock(&(pvt->lock));
	ret = scan_areas_and_find_fit(tcm, w, h, align, area);
	if (!ret)
		/* update map */
		fill_area(tcm, area, area);

	spin_unlock(&(pvt->lock));
	return ret;
}

/**
 * Unreserve a previously allocated 2D or 1D area
 * @param area	area to be freed
 * @return 0 - success
 */
static s32 sita_free(struct tcm *tcm, struct tcm_area *area)
{
	struct sita_pvt *pvt = (struct sita_pvt *)tcm->pvt;

	spin_lock(&(pvt->lock));

	/* check that this is in fact an existing area */
	WARN_ON(pvt->map[area->p0.x][area->p0.y] != area ||
		pvt->map[area->p1.x][area->p1.y] != area);

	/* Clear the contents of the associated tiles in the map */
	fill_area(tcm, area, NULL);

	spin_unlock(&(pvt->lock));

	return 0;
}

/**
 * Note: In general the cordinates in the scan field area relevant to the can
 * sweep directions. The scan origin (e.g. top-left corner) will always be
 * the p0 member of the field.  Therfore, for a scan from top-left p0.x <= p1.x
 * and p0.y <= p1.y; whereas, for a scan from bottom-right p1.x <= p0.x and p1.y
 * <= p0.y
 */

/**
 * Raster scan horizontally right to left from top to bottom to find a place for
 * a 2D area of given size inside a scan field.
 *
 * @param w	width of desired area
 * @param h	height of desired area
 * @param align	desired area alignment
 * @param area	pointer to the area that will be set to the best position
 * @param field	area to scan (inclusive)
 *
 * @return 0 on success, non-0 error value on failure.
 */
static s32 scan_r2l_t2b(struct tcm *tcm, u16 w, u16 h, u16 align,
			struct tcm_area *field, struct tcm_area *area)
{
	s32 x, y;
	s16 start_x, end_x, start_y, end_y, found_x = -1;
	struct tcm_area ***map = ((struct sita_pvt *)tcm->pvt)->map;
	struct score best = {{0}, {0}, {0}, 0};

	start_x = field->p0.x;
	end_x = field->p1.x;
	start_y = field->p0.y;
	end_y = field->p1.y;

	/* check scan area co-ordinates */
	if (field->p0.x < field->p1.x ||
	    field->p1.y < field->p0.y)
		return -EINVAL;

	/* check if allocation would fit in scan area */
	if (w > LEN(start_x, end_x) || h > LEN(end_y, start_y))
		return -ENOSPC;

	/* adjust start_x and end_y, as allocation would not fit beyond */
	start_x = ALIGN_DOWN(start_x - w + 1, align); /* - 1 to be inclusive */
	end_y = end_y - h + 1;

	/* check if allocation would still fit in scan area */
	if (start_x < end_x)
		return -ENOSPC;

	/* scan field top-to-bottom, right-to-left */
	for (y = start_y; y <= end_y; y++) {
		for (x = start_x; x >= end_x; x -= align) {
			if (is_area_free(map, x, y, w, h)) {
				found_x = x;

				/* update best candidate */
				if (update_candidate(tcm, x, y, w, h, field,
							CR_R2L_T2B, &best))
					goto done;

				/* change upper x bound */
				end_x = x + 1;
				break;
			} else if (map[x][y] && map[x][y]->is2d) {
				/* step over 2D areas */
				x = ALIGN(map[x][y]->p0.x - w + 1, align);
			}
		}

		/* break if you find a free area shouldering the scan field */
		if (found_x == start_x)
			break;
	}

	if (!best.a.tcm)
		return -ENOSPC;
done:
	assign(area, best.a.p0.x, best.a.p0.y, best.a.p1.x, best.a.p1.y);
	return 0;
}

/**
 * Raster scan horizontally left to right from top to bottom to find a place for
 * a 2D area of given size inside a scan field.
 *
 * @param w	width of desired area
 * @param h	height of desired area
 * @param align	desired area alignment
 * @param area	pointer to the area that will be set to the best position
 * @param field	area to scan (inclusive)
 *
 * @return 0 on success, non-0 error value on failure.
 */
static s32 scan_l2r_t2b(struct tcm *tcm, u16 w, u16 h, u16 align,
			struct tcm_area *field, struct tcm_area *area)
{
	s32 x, y;
	s16 start_x, end_x, start_y, end_y, found_x = -1;
	struct tcm_area ***map = ((struct sita_pvt *)tcm->pvt)->map;
	struct score best = {{0}, {0}, {0}, 0};

	start_x = field->p0.x;
	end_x = field->p1.x;
	start_y = field->p0.y;
	end_y = field->p1.y;

	/* check scan area co-ordinates */
	if (field->p1.x < field->p0.x ||
	    field->p1.y < field->p0.y)
		return -EINVAL;

	/* check if allocation would fit in scan area */
	if (w > LEN(end_x, start_x) || h > LEN(end_y, start_y))
		return -ENOSPC;

	start_x = ALIGN(start_x, align);

	/* check if allocation would still fit in scan area */
	if (w > LEN(end_x, start_x))
		return -ENOSPC;

	/* adjust end_x and end_y, as allocation would not fit beyond */
	end_x = end_x - w + 1; /* + 1 to be inclusive */
	end_y = end_y - h + 1;

	/* scan field top-to-bottom, left-to-right */
	for (y = start_y; y <= end_y; y++) {
		for (x = start_x; x <= end_x; x += align) {
			if (is_area_free(map, x, y, w, h)) {
				found_x = x;

				/* update best candidate */
				if (update_candidate(tcm, x, y, w, h, field,
							CR_L2R_T2B, &best))
					goto done;
				/* change upper x bound */
				end_x = x - 1;

				break;
			} else if (map[x][y] && map[x][y]->is2d) {
				/* step over 2D areas */
				x = ALIGN_DOWN(map[x][y]->p1.x, align);
			}
		}

		/* break if you find a free area shouldering the scan field */
		if (found_x == start_x)
			break;
	}

	if (!best.a.tcm)
		return -ENOSPC;
done:
	assign(area, best.a.p0.x, best.a.p0.y, best.a.p1.x, best.a.p1.y);
	return 0;
}

/**
 * Raster scan horizontally right to left from bottom to top to find a place
 * for a 1D area of given size inside a scan field.
 *
 * @param num_slots	size of desired area
 * @param align		desired area alignment
 * @param area		pointer to the area that will be set to the best
 *			position
 * @param field		area to scan (inclusive)
 *
 * @return 0 on success, non-0 error value on failure.
 */
static s32 scan_r2l_b2t_one_dim(struct tcm *tcm, u32 num_slots,
				struct tcm_area *field, struct tcm_area *area)
{
	s32 found = 0;
	s16 x, y;
	struct sita_pvt *pvt = (struct sita_pvt *)tcm->pvt;
	struct tcm_area *p;

	/* check scan area co-ordinates */
	if (field->p0.y < field->p1.y)
		return -EINVAL;

	/**
	 * Currently we only support full width 1D scan field, which makes sense
	 * since 1D slot-ordering spans the full container width.
	 */
	if (tcm->width != field->p0.x - field->p1.x + 1)
		return -EINVAL;

	/* check if allocation would fit in scan area */
	if (num_slots > tcm->width * LEN(field->p0.y, field->p1.y))
		return -ENOSPC;

	x = field->p0.x;
	y = field->p0.y;

	/* find num_slots consecutive free slots to the left */
	while (found < num_slots) {
		if (y < 0)
			return -ENOSPC;

		/* remember bottom-right corner */
		if (found == 0) {
			area->p1.x = x;
			area->p1.y = y;
		}

		/* skip busy regions */
		p = pvt->map[x][y];
		if (p) {
			/* move to left of 2D areas, top left of 1D */
			x = p->p0.x;
			if (!p->is2d)
				y = p->p0.y;

			/* start over */
			found = 0;
		} else {
			/* count consecutive free slots */
			found++;
			if (found == num_slots)
				break;
		}

		/* move to the left */
		if (x == 0)
			y--;
		x = (x ? : tcm->width) - 1;

	}

	/* set top-left corner */
	area->p0.x = x;
	area->p0.y = y;
	return 0;
}

/**
 * Find a place for a 2D area of given size inside a scan field based on its
 * alignment needs.
 *
 * @param w	width of desired area
 * @param h	height of desired area
 * @param align	desired area alignment
 * @param area	pointer to the area that will be set to the best position
 *
 * @return 0 on success, non-0 error value on failure.
 */
static s32 scan_areas_and_find_fit(struct tcm *tcm, u16 w, u16 h, u16 align,
				   struct tcm_area *area)
{
	s32 ret = 0;
	struct tcm_area field = {0};
	u16 boundary_x, boundary_y;
	struct sita_pvt *pvt = (struct sita_pvt *)tcm->pvt;

	if (align > 1) {
		/* prefer top-left corner */
		boundary_x = pvt->div_pt.x - 1;
		boundary_y = pvt->div_pt.y - 1;

		/* expand width and height if needed */
		if (w > pvt->div_pt.x)
			boundary_x = tcm->width - 1;
		if (h > pvt->div_pt.y)
			boundary_y = tcm->height - 1;

		assign(&field, 0, 0, boundary_x, boundary_y);
		ret = scan_l2r_t2b(tcm, w, h, align, &field, area);

		/* scan whole container if failed, but do not scan 2x */
		if (ret != 0 && (boundary_x != tcm->width - 1 ||
				 boundary_y != tcm->height - 1)) {
			/* scan the entire container if nothing found */
			assign(&field, 0, 0, tcm->width - 1, tcm->height - 1);
			ret = scan_l2r_t2b(tcm, w, h, align, &field, area);
		}
	} else if (align == 1) {
		/* prefer top-right corner */
		boundary_x = pvt->div_pt.x;
		boundary_y = pvt->div_pt.y - 1;

		/* expand width and height if needed */
		if (w > (tcm->width - pvt->div_pt.x))
			boundary_x = 0;
		if (h > pvt->div_pt.y)
			boundary_y = tcm->height - 1;

		assign(&field, tcm->width - 1, 0, boundary_x, boundary_y);
		ret = scan_r2l_t2b(tcm, w, h, align, &field, area);

		/* scan whole container if failed, but do not scan 2x */
		if (ret != 0 && (boundary_x != 0 ||
				 boundary_y != tcm->height - 1)) {
			/* scan the entire container if nothing found */
			assign(&field, tcm->width - 1, 0, 0, tcm->height - 1);
			ret = scan_r2l_t2b(tcm, w, h, align, &field,
					   area);
		}
	}

	return ret;
}

/* check if an entire area is free */
static s32 is_area_free(struct tcm_area ***map, u16 x0, u16 y0, u16 w, u16 h)
{
	u16 x = 0, y = 0;
	for (y = y0; y < y0 + h; y++) {
		for (x = x0; x < x0 + w; x++) {
			if (map[x][y])
				return false;
		}
	}
	return true;
}

/* fills an area with a parent tcm_area */
static void fill_area(struct tcm *tcm, struct tcm_area *area,
			struct tcm_area *parent)
{
	s32 x, y;
	struct sita_pvt *pvt = (struct sita_pvt *)tcm->pvt;
	struct tcm_area a, a_;

	/* set area's tcm; otherwise, enumerator considers it invalid */
	area->tcm = tcm;

	tcm_for_each_slice(a, *area, a_) {
		for (x = a.p0.x; x <= a.p1.x; ++x)
			for (y = a.p0.y; y <= a.p1.y; ++y)
				pvt->map[x][y] = parent;

	}
}

/**
 * Compares a candidate area to the current best area, and if it is a better
 * fit, it updates the best to this one.
 *
 * @param x0, y0, w, h		top, left, width, height of candidate area
 * @param field			scan field
 * @param criteria		scan criteria
 * @param best			best candidate and its scores
 *
 * @return 1 (true) if the candidate area is known to be the final best, so no
 * more searching should be performed
 */
static s32 update_candidate(struct tcm *tcm, u16 x0, u16 y0, u16 w, u16 h,
			    struct tcm_area *field, s32 criteria,
			    struct score *best)
{
	struct score me;	/* score for area */

	/*
	 * NOTE: For horizontal bias we always give the first found, because our
	 * scan is horizontal-raster-based and the first candidate will always
	 * have the horizontal bias.
	 */
	bool first = criteria & CR_BIAS_HORIZONTAL;

	assign(&me.a, x0, y0, x0 + w - 1, y0 + h - 1);

	/* calculate score for current candidate */
	if (!first) {
		get_neighbor_stats(tcm, &me.a, &me.n);
		me.neighs = me.n.edge + me.n.busy;
		get_nearness_factor(field, &me.a, &me.f);
	}

	/* the 1st candidate is always the best */
	if (!best->a.tcm)
		goto better;

	BUG_ON(first);

	/* diagonal balance check */
	if ((criteria & CR_DIAGONAL_BALANCE) &&
		best->neighs <= me.neighs &&
		(best->neighs < me.neighs ||
		 /* this implies that neighs and occupied match */
		 best->n.busy < me.n.busy ||
		 (best->n.busy == me.n.busy &&
		  /* check the nearness factor */
		  best->f.x + best->f.y > me.f.x + me.f.y)))
		goto better;

	/* not better, keep going */
	return 0;

better:
	/* save current area as best */
	memcpy(best, &me, sizeof(me));
	best->a.tcm = tcm;
	return first;
}

/**
 * Calculate the nearness factor of an area in a search field.  The nearness
 * factor is smaller if the area is closer to the search origin.
 */
static void get_nearness_factor(struct tcm_area *field, struct tcm_area *area,
				struct nearness_factor *nf)
{
	/**
	 * Using signed math as field coordinates may be reversed if
	 * search direction is right-to-left or bottom-to-top.
	 */
	nf->x = (s32)(area->p0.x - field->p0.x) * 1000 /
		(field->p1.x - field->p0.x);
	nf->y = (s32)(area->p0.y - field->p0.y) * 1000 /
		(field->p1.y - field->p0.y);
}

/* get neighbor statistics */
static void get_neighbor_stats(struct tcm *tcm, struct tcm_area *area,
			 struct neighbor_stats *stat)
{
	s16 x = 0, y = 0;
	struct sita_pvt *pvt = (struct sita_pvt *)tcm->pvt;

	/* Clearing any exisiting values */
	memset(stat, 0, sizeof(*stat));

	/* process top & bottom edges */
	for (x = area->p0.x; x <= area->p1.x; x++) {
		if (area->p0.y == 0)
			stat->edge++;
		else if (pvt->map[x][area->p0.y - 1])
			stat->busy++;

		if (area->p1.y == tcm->height - 1)
			stat->edge++;
		else if (pvt->map[x][area->p1.y + 1])
			stat->busy++;
	}

	/* process left & right edges */
	for (y = area->p0.y; y <= area->p1.y; ++y) {
		if (area->p0.x == 0)
			stat->edge++;
		else if (pvt->map[area->p0.x - 1][y])
			stat->busy++;

		if (area->p1.x == tcm->width - 1)
			stat->edge++;
		else if (pvt->map[area->p1.x + 1][y])
			stat->busy++;
	}
}