/*
 * UWB reservation management.
 *
 * Copyright (C) 2008 Cambridge Silicon Radio Ltd.
 *
 * This program 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 program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/uwb.h>

#include "uwb-internal.h"

static void uwb_rsv_fill_column_alloc(struct uwb_rsv_alloc_info *ai)
{
	int col, mas, safe_mas, unsafe_mas;
	unsigned char *bm = ai->bm;
	struct uwb_rsv_col_info *ci = ai->ci;
	unsigned char c;

	for (col = ci->csi.start_col; col < UWB_NUM_ZONES; col += ci->csi.interval) {
    
		safe_mas   = ci->csi.safe_mas_per_col;
		unsafe_mas = ci->csi.unsafe_mas_per_col;
    
		for (mas = 0; mas < UWB_MAS_PER_ZONE; mas++ ) {
			if (bm[col * UWB_MAS_PER_ZONE + mas] == 0) {
	
				if (safe_mas > 0) {
					safe_mas--;
					c = UWB_RSV_MAS_SAFE;
				} else if (unsafe_mas > 0) {
					unsafe_mas--;
					c = UWB_RSV_MAS_UNSAFE;
				} else {
					break;
				}
				bm[col * UWB_MAS_PER_ZONE + mas] = c;
			}
		}
	}
}

static void uwb_rsv_fill_row_alloc(struct uwb_rsv_alloc_info *ai)
{
	int mas, col, rows;
	unsigned char *bm = ai->bm;
	struct uwb_rsv_row_info *ri = &ai->ri;
	unsigned char c;

	rows = 1;
	c = UWB_RSV_MAS_SAFE;
	for (mas = UWB_MAS_PER_ZONE - 1; mas >= 0; mas--) {
		if (ri->avail[mas] == 1) {
      
			if (rows > ri->used_rows) {
				break;
			} else if (rows > 7) {
				c = UWB_RSV_MAS_UNSAFE;
			}

			for (col = 0; col < UWB_NUM_ZONES; col++) {
				if (bm[col * UWB_NUM_ZONES + mas] != UWB_RSV_MAS_NOT_AVAIL) {
					bm[col * UWB_NUM_ZONES + mas] = c;
					if(c == UWB_RSV_MAS_SAFE)
						ai->safe_allocated_mases++;
					else
						ai->unsafe_allocated_mases++;
				}
			}
			rows++;
		}
	}
	ai->total_allocated_mases = ai->safe_allocated_mases + ai->unsafe_allocated_mases;
}

/*
 * Find the best column set for a given availability, interval, num safe mas and
 * num unsafe mas.
 *
 * The different sets are tried in order as shown below, depending on the interval.
 *
 * interval = 16
 *	deep = 0
 *		set 1 ->  {  8 }
 *	deep = 1
 *		set 1 ->  {  4 }
 *		set 2 ->  { 12 }
 *	deep = 2
 *		set 1 ->  {  2 }
 *		set 2 ->  {  6 }
 *		set 3 ->  { 10 }
 *		set 4 ->  { 14 }
 *	deep = 3
 *		set 1 ->  {  1 }
 *		set 2 ->  {  3 }
 *		set 3 ->  {  5 }
 *		set 4 ->  {  7 }
 *		set 5 ->  {  9 }
 *		set 6 ->  { 11 }
 *		set 7 ->  { 13 }
 *		set 8 ->  { 15 }
 *
 * interval = 8
 *	deep = 0
 *		set 1 ->  {  4  12 }
 *	deep = 1
 *		set 1 ->  {  2  10 }
 *		set 2 ->  {  6  14 }
 *	deep = 2
 *		set 1 ->  {  1   9 }
 *		set 2 ->  {  3  11 }
 *		set 3 ->  {  5  13 }
 *		set 4 ->  {  7  15 }
 *
 * interval = 4
 *	deep = 0
 *		set 1 ->  {  2   6  10  14 }
 *	deep = 1
 *		set 1 ->  {  1   5   9  13 }
 *		set 2 ->  {  3   7  11  15 }
 *
 * interval = 2
 *	deep = 0
 *		set 1 ->  {  1   3   5   7   9  11  13  15 }
 */
static int uwb_rsv_find_best_column_set(struct uwb_rsv_alloc_info *ai, int interval, 
					int num_safe_mas, int num_unsafe_mas)
{
	struct uwb_rsv_col_info *ci = ai->ci;
	struct uwb_rsv_col_set_info *csi = &ci->csi;
	struct uwb_rsv_col_set_info tmp_csi;
	int deep, set, col, start_col_deep, col_start_set;
	int start_col, max_mas_in_set, lowest_max_mas_in_deep;
	int n_mas;
	int found = UWB_RSV_ALLOC_NOT_FOUND; 

	tmp_csi.start_col = 0;
	start_col_deep = interval;
	n_mas = num_unsafe_mas + num_safe_mas;

	for (deep = 0; ((interval >> deep) & 0x1) == 0; deep++) {
		start_col_deep /= 2;
		col_start_set = 0;
		lowest_max_mas_in_deep = UWB_MAS_PER_ZONE;

		for (set = 1; set <= (1 << deep); set++) {
			max_mas_in_set = 0;
			start_col = start_col_deep + col_start_set;
			for (col = start_col; col < UWB_NUM_ZONES; col += interval) {
                
				if (ci[col].max_avail_safe >= num_safe_mas &&
				    ci[col].max_avail_unsafe >= n_mas) {
					if (ci[col].highest_mas[n_mas] > max_mas_in_set)
						max_mas_in_set = ci[col].highest_mas[n_mas];
				} else {
					max_mas_in_set = 0;
					break;
				}
			}
			if ((lowest_max_mas_in_deep > max_mas_in_set) && max_mas_in_set) {
				lowest_max_mas_in_deep = max_mas_in_set;

				tmp_csi.start_col = start_col;
			}
			col_start_set += (interval >> deep);
		}

		if (lowest_max_mas_in_deep < 8) {
			csi->start_col = tmp_csi.start_col;
			found = UWB_RSV_ALLOC_FOUND;
			break;
		} else if ((lowest_max_mas_in_deep > 8) && 
			   (lowest_max_mas_in_deep != UWB_MAS_PER_ZONE) &&
			   (found == UWB_RSV_ALLOC_NOT_FOUND)) {
			csi->start_col = tmp_csi.start_col;
			found = UWB_RSV_ALLOC_FOUND;
		}
	}

	if (found == UWB_RSV_ALLOC_FOUND) {
		csi->interval = interval;
		csi->safe_mas_per_col = num_safe_mas;
		csi->unsafe_mas_per_col = num_unsafe_mas;

		ai->safe_allocated_mases = (UWB_NUM_ZONES / interval) * num_safe_mas;
		ai->unsafe_allocated_mases = (UWB_NUM_ZONES / interval) * num_unsafe_mas;
		ai->total_allocated_mases = ai->safe_allocated_mases + ai->unsafe_allocated_mases;
		ai->interval = interval;		
	}
	return found;
}

static void get_row_descriptors(struct uwb_rsv_alloc_info *ai)
{
	unsigned char *bm = ai->bm;
	struct uwb_rsv_row_info *ri = &ai->ri;
	int col, mas;
  
	ri->free_rows = 16;
	for (mas = 0; mas < UWB_MAS_PER_ZONE; mas ++) {
		ri->avail[mas] = 1;
		for (col = 1; col < UWB_NUM_ZONES; col++) {
			if (bm[col * UWB_NUM_ZONES + mas] == UWB_RSV_MAS_NOT_AVAIL) {
				ri->free_rows--;
				ri->avail[mas]=0;
				break;
			}
		}
	}
}

static void uwb_rsv_fill_column_info(unsigned char *bm, int column, struct uwb_rsv_col_info *rci)
{
	int mas;
	int block_count = 0, start_block = 0; 
	int previous_avail = 0;
	int available = 0;
	int safe_mas_in_row[UWB_MAS_PER_ZONE] = {
		8, 7, 6, 5, 4, 4, 4, 4, 4, 4, 4, 4, 4, 3, 2, 1,
	};

	rci->max_avail_safe = 0;

	for (mas = 0; mas < UWB_MAS_PER_ZONE; mas ++) {
		if (!bm[column * UWB_NUM_ZONES + mas]) {
			available++;
			rci->max_avail_unsafe = available;

			rci->highest_mas[available] = mas;

			if (previous_avail) {
				block_count++;
				if ((block_count > safe_mas_in_row[start_block]) &&
				    (!rci->max_avail_safe))
					rci->max_avail_safe = available - 1;
			} else {
				previous_avail = 1;
				start_block = mas;
				block_count = 1;
			}
		} else {
			previous_avail = 0;
		}
	}
	if (!rci->max_avail_safe)
		rci->max_avail_safe = rci->max_avail_unsafe;
}

static void get_column_descriptors(struct uwb_rsv_alloc_info *ai)
{
	unsigned char *bm = ai->bm;
	struct uwb_rsv_col_info *ci = ai->ci;
	int col;

	for (col = 1; col < UWB_NUM_ZONES; col++) {
		uwb_rsv_fill_column_info(bm, col, &ci[col]);
	}
}

static int uwb_rsv_find_best_row_alloc(struct uwb_rsv_alloc_info *ai)
{
	int n_rows;
	int max_rows = ai->max_mas / UWB_USABLE_MAS_PER_ROW;
	int min_rows = ai->min_mas / UWB_USABLE_MAS_PER_ROW;
	if (ai->min_mas % UWB_USABLE_MAS_PER_ROW)
		min_rows++;
	for (n_rows = max_rows; n_rows >= min_rows; n_rows--) {
		if (n_rows <= ai->ri.free_rows) {
			ai->ri.used_rows = n_rows;
			ai->interval = 1; /* row reservation */
			uwb_rsv_fill_row_alloc(ai);
			return UWB_RSV_ALLOC_FOUND;
		}
	}  
	return UWB_RSV_ALLOC_NOT_FOUND;
}

static int uwb_rsv_find_best_col_alloc(struct uwb_rsv_alloc_info *ai, int interval)
{
	int n_safe, n_unsafe, n_mas;  
	int n_column = UWB_NUM_ZONES / interval;
	int max_per_zone = ai->max_mas / n_column;
	int min_per_zone = ai->min_mas / n_column;

	if (ai->min_mas % n_column)
		min_per_zone++;

	if (min_per_zone > UWB_MAS_PER_ZONE) {
		return UWB_RSV_ALLOC_NOT_FOUND;
	}
    
	if (max_per_zone > UWB_MAS_PER_ZONE) {
		max_per_zone = UWB_MAS_PER_ZONE;
	}
    
	for (n_mas = max_per_zone; n_mas >= min_per_zone; n_mas--) {
		if (uwb_rsv_find_best_column_set(ai, interval, 0, n_mas) == UWB_RSV_ALLOC_NOT_FOUND)
			continue;
		for (n_safe = n_mas; n_safe >= 0; n_safe--) {
			n_unsafe = n_mas - n_safe;
			if (uwb_rsv_find_best_column_set(ai, interval, n_safe, n_unsafe) == UWB_RSV_ALLOC_FOUND) {
				uwb_rsv_fill_column_alloc(ai);
				return UWB_RSV_ALLOC_FOUND;
			}
		}
	}
	return UWB_RSV_ALLOC_NOT_FOUND;
}

int uwb_rsv_find_best_allocation(struct uwb_rsv *rsv, struct uwb_mas_bm *available, 
				 struct uwb_mas_bm *result)
{
	struct uwb_rsv_alloc_info *ai;
	int interval;
	int bit_index;

	ai = kzalloc(sizeof(struct uwb_rsv_alloc_info), GFP_KERNEL);
	if (!ai)
		return UWB_RSV_ALLOC_NOT_FOUND;
	ai->min_mas = rsv->min_mas;
	ai->max_mas = rsv->max_mas;
	ai->max_interval = rsv->max_interval;


	/* fill the not available vector from the available bm */
	for (bit_index = 0; bit_index < UWB_NUM_MAS; bit_index++) {
		if (!test_bit(bit_index, available->bm))
			ai->bm[bit_index] = UWB_RSV_MAS_NOT_AVAIL;
	}

	if (ai->max_interval == 1) {
		get_row_descriptors(ai);
		if (uwb_rsv_find_best_row_alloc(ai) == UWB_RSV_ALLOC_FOUND)
			goto alloc_found;
		else
			goto alloc_not_found;
	}

	get_column_descriptors(ai);
        
	for (interval = 16; interval >= 2; interval>>=1) {
		if (interval > ai->max_interval)
			continue;
		if (uwb_rsv_find_best_col_alloc(ai, interval) == UWB_RSV_ALLOC_FOUND)
			goto alloc_found;
	}

	/* try row reservation if no column is found */
	get_row_descriptors(ai);
	if (uwb_rsv_find_best_row_alloc(ai) == UWB_RSV_ALLOC_FOUND)
		goto alloc_found;
	else
		goto alloc_not_found;

  alloc_found:
	bitmap_zero(result->bm, UWB_NUM_MAS);
	bitmap_zero(result->unsafe_bm, UWB_NUM_MAS);
	/* fill the safe and unsafe bitmaps */
	for (bit_index = 0; bit_index < UWB_NUM_MAS; bit_index++) {
		if (ai->bm[bit_index] == UWB_RSV_MAS_SAFE)
			set_bit(bit_index, result->bm);
		else if (ai->bm[bit_index] == UWB_RSV_MAS_UNSAFE)
			set_bit(bit_index, result->unsafe_bm);
	}
	bitmap_or(result->bm, result->bm, result->unsafe_bm, UWB_NUM_MAS);

	result->safe   = ai->safe_allocated_mases;
	result->unsafe = ai->unsafe_allocated_mases;
	
	kfree(ai);		
	return UWB_RSV_ALLOC_FOUND;
  
  alloc_not_found:
	kfree(ai);
	return UWB_RSV_ALLOC_NOT_FOUND;
}