/*
 * Register cache access API - rbtree caching support
 *
 * Copyright 2011 Wolfson Microelectronics plc
 *
 * Author: Dimitris Papastamos <dp@opensource.wolfsonmicro.com>
 *
 * 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.
 */

#include <linux/debugfs.h>
#include <linux/device.h>
#include <linux/rbtree.h>
#include <linux/seq_file.h>
#include <linux/slab.h>

#include "internal.h"

static int regcache_rbtree_write(struct regmap *map, unsigned int reg,
                                 unsigned int value);
static int regcache_rbtree_exit(struct regmap *map);

struct regcache_rbtree_node {
        /* block of adjacent registers */
        void *block;
        /* Which registers are present */
        long *cache_present;
        /* base register handled by this block */
        unsigned int base_reg;
        /* number of registers available in the block */
        unsigned int blklen;
        /* the actual rbtree node holding this block */
        struct rb_node node;
} __attribute__ ((packed));

struct regcache_rbtree_ctx {
        struct rb_root root;
        struct regcache_rbtree_node *cached_rbnode;
};

static inline void regcache_rbtree_get_base_top_reg(
        struct regmap *map,
        struct regcache_rbtree_node *rbnode,
        unsigned int *base, unsigned int *top)
{
        *base = rbnode->base_reg;
        *top = rbnode->base_reg + ((rbnode->blklen - 1) * map->reg_stride);
}

static unsigned int regcache_rbtree_get_register(struct regmap *map,
        struct regcache_rbtree_node *rbnode, unsigned int idx)
{
        return regcache_get_val(map, rbnode->block, idx);
}

static void regcache_rbtree_set_register(struct regmap *map,
                                         struct regcache_rbtree_node *rbnode,
                                         unsigned int idx, unsigned int val)
{
        set_bit(idx, rbnode->cache_present);
        regcache_set_val(map, rbnode->block, idx, val);
}

static struct regcache_rbtree_node *regcache_rbtree_lookup(struct regmap *map,
                                                           unsigned int reg)
{
        struct regcache_rbtree_ctx *rbtree_ctx = map->cache;
        struct rb_node *node;
        struct regcache_rbtree_node *rbnode;
        unsigned int base_reg, top_reg;

        rbnode = rbtree_ctx->cached_rbnode;
        if (rbnode) {
                regcache_rbtree_get_base_top_reg(map, rbnode, &base_reg,
                                                 &top_reg);
                if (reg >= base_reg && reg <= top_reg)
                        return rbnode;
        }

        node = rbtree_ctx->root.rb_node;
        while (node) {
                rbnode = rb_entry(node, struct regcache_rbtree_node, node);
                regcache_rbtree_get_base_top_reg(map, rbnode, &base_reg,
                                                 &top_reg);
                if (reg >= base_reg && reg <= top_reg) {
                        rbtree_ctx->cached_rbnode = rbnode;
                        return rbnode;
                } else if (reg > top_reg) {
                        node = node->rb_right;
                } else if (reg < base_reg) {
                        node = node->rb_left;
                }
        }

        return NULL;
}

static int regcache_rbtree_insert(struct regmap *map, struct rb_root *root,
                                  struct regcache_rbtree_node *rbnode)
{
        struct rb_node **new, *parent;
        struct regcache_rbtree_node *rbnode_tmp;
        unsigned int base_reg_tmp, top_reg_tmp;
        unsigned int base_reg;

        parent = NULL;
        new = &root->rb_node;
        while (*new) {
                rbnode_tmp = rb_entry(*new, struct regcache_rbtree_node, node);
                /* base and top registers of the current rbnode */
                regcache_rbtree_get_base_top_reg(map, rbnode_tmp, &base_reg_tmp,
                                                 &top_reg_tmp);
                /* base register of the rbnode to be added */
                base_reg = rbnode->base_reg;
                parent = *new;
                /* if this register has already been inserted, just return */
                if (base_reg >= base_reg_tmp &&
                    base_reg <= top_reg_tmp)
                        return 0;
                else if (base_reg > top_reg_tmp)
                        new = &((*new)->rb_right);
                else if (base_reg < base_reg_tmp)
                        new = &((*new)->rb_left);
        }

        /* insert the node into the rbtree */
        rb_link_node(&rbnode->node, parent, new);
        rb_insert_color(&rbnode->node, root);

        return 1;
}

#ifdef CONFIG_DEBUG_FS
static int rbtree_show(struct seq_file *s, void *ignored)
{
        struct regmap *map = s->private;
        struct regcache_rbtree_ctx *rbtree_ctx = map->cache;
        struct regcache_rbtree_node *n;
        struct rb_node *node;
        unsigned int base, top;
        size_t mem_size;
        int nodes = 0;
        int registers = 0;
        int this_registers, average;

        map->lock(map->lock_arg);

        mem_size = sizeof(*rbtree_ctx);

        for (node = rb_first(&rbtree_ctx->root); node != NULL;
             node = rb_next(node)) {
                n = rb_entry(node, struct regcache_rbtree_node, node);
                mem_size += sizeof(*n);
                mem_size += (n->blklen * map->cache_word_size);
                mem_size += BITS_TO_LONGS(n->blklen) * sizeof(long);

                regcache_rbtree_get_base_top_reg(map, n, &base, &top);
                this_registers = ((top - base) / map->reg_stride) + 1;
                seq_printf(s, "%x-%x (%d)\n", base, top, this_registers);

                nodes++;
                registers += this_registers;
        }

        if (nodes)
                average = registers / nodes;
        else
                average = 0;

        seq_printf(s, "%d nodes, %d registers, average %d registers, used %zu bytes\n",
                   nodes, registers, average, mem_size);

        map->unlock(map->lock_arg);

        return 0;
}

static int rbtree_open(struct inode *inode, struct file *file)
{
        return single_open(file, rbtree_show, inode->i_private);
}

static const struct file_operations rbtree_fops = {
        .open           = rbtree_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = single_release,
};

static void rbtree_debugfs_init(struct regmap *map)
{
        debugfs_create_file("rbtree", 0400, map->debugfs, map, &rbtree_fops);
}
#endif

static int regcache_rbtree_init(struct regmap *map)
{
        struct regcache_rbtree_ctx *rbtree_ctx;
        int i;
        int ret;

        map->cache = kmalloc(sizeof *rbtree_ctx, GFP_KERNEL);
        if (!map->cache)
                return -ENOMEM;

        rbtree_ctx = map->cache;
        rbtree_ctx->root = RB_ROOT;
        rbtree_ctx->cached_rbnode = NULL;

        for (i = 0; i < map->num_reg_defaults; i++) {
                ret = regcache_rbtree_write(map,
                                            map->reg_defaults[i].reg,
                                            map->reg_defaults[i].def);
                if (ret)
                        goto err;
        }

        return 0;

err:
        regcache_rbtree_exit(map);
        return ret;
}

static int regcache_rbtree_exit(struct regmap *map)
{
        struct rb_node *next;
        struct regcache_rbtree_ctx *rbtree_ctx;
        struct regcache_rbtree_node *rbtree_node;

        /* if we've already been called then just return */
        rbtree_ctx = map->cache;
        if (!rbtree_ctx)
                return 0;

        /* free up the rbtree */
        next = rb_first(&rbtree_ctx->root);
        while (next) {
                rbtree_node = rb_entry(next, struct regcache_rbtree_node, node);
                next = rb_next(&rbtree_node->node);
                rb_erase(&rbtree_node->node, &rbtree_ctx->root);
                kfree(rbtree_node->cache_present);
                kfree(rbtree_node->block);
                kfree(rbtree_node);
        }

        /* release the resources */
        kfree(map->cache);
        map->cache = NULL;

        return 0;
}

static int regcache_rbtree_read(struct regmap *map,
                                unsigned int reg, unsigned int *value)
{
        struct regcache_rbtree_node *rbnode;
        unsigned int reg_tmp;

        rbnode = regcache_rbtree_lookup(map, reg);
        if (rbnode) {
                reg_tmp = (reg - rbnode->base_reg) / map->reg_stride;
                if (!test_bit(reg_tmp, rbnode->cache_present))
                        return -ENOENT;
                *value = regcache_rbtree_get_register(map, rbnode, reg_tmp);
        } else {
                return -ENOENT;
        }

        return 0;
}


static int regcache_rbtree_insert_to_block(struct regmap *map,
                                           struct regcache_rbtree_node *rbnode,
                                           unsigned int base_reg,
                                           unsigned int top_reg,
                                           unsigned int reg,
                                           unsigned int value)
{
        unsigned int blklen;
        unsigned int pos, offset;
        unsigned long *present;
        u8 *blk;

        blklen = (top_reg - base_reg) / map->reg_stride + 1;
        pos = (reg - base_reg) / map->reg_stride;
        offset = (rbnode->base_reg - base_reg) / map->reg_stride;

        blk = krealloc(rbnode->block,
                       blklen * map->cache_word_size,
                       GFP_KERNEL);
        if (!blk)
                return -ENOMEM;

        if (BITS_TO_LONGS(blklen) > BITS_TO_LONGS(rbnode->blklen)) {
                present = krealloc(rbnode->cache_present,
                                   BITS_TO_LONGS(blklen) * sizeof(*present),
                                   GFP_KERNEL);
                if (!present) {
                        kfree(blk);
                        return -ENOMEM;
                }

                memset(present + BITS_TO_LONGS(rbnode->blklen), 0,
                       (BITS_TO_LONGS(blklen) - BITS_TO_LONGS(rbnode->blklen))
                       * sizeof(*present));
        } else {
                present = rbnode->cache_present;
        }

        /* insert the register value in the correct place in the rbnode block */
        if (pos == 0) {
                memmove(blk + offset * map->cache_word_size,
                        blk, rbnode->blklen * map->cache_word_size);
                bitmap_shift_left(present, present, offset, blklen);
        }

        /* update the rbnode block, its size and the base register */
        rbnode->block = blk;
        rbnode->blklen = blklen;
        rbnode->base_reg = base_reg;
        rbnode->cache_present = present;

        regcache_rbtree_set_register(map, rbnode, pos, value);
        return 0;
}

static struct regcache_rbtree_node *
regcache_rbtree_node_alloc(struct regmap *map, unsigned int reg)
{
        struct regcache_rbtree_node *rbnode;
        const struct regmap_range *range;
        int i;

        rbnode = kzalloc(sizeof(*rbnode), GFP_KERNEL);
        if (!rbnode)
                return NULL;

        /* If there is a read table then use it to guess at an allocation */
        if (map->rd_table) {
                for (i = 0; i < map->rd_table->n_yes_ranges; i++) {
                        if (regmap_reg_in_range(reg,
                                                &map->rd_table->yes_ranges[i]))
                                break;
                }

                if (i != map->rd_table->n_yes_ranges) {
                        range = &map->rd_table->yes_ranges[i];
                        rbnode->blklen = (range->range_max - range->range_min) /
                                map->reg_stride + 1;
                        rbnode->base_reg = range->range_min;
                }
        }

        if (!rbnode->blklen) {
                rbnode->blklen = 1;
                rbnode->base_reg = reg;
        }

        rbnode->block = kmalloc_array(rbnode->blklen, map->cache_word_size,
                                      GFP_KERNEL);
        if (!rbnode->block)
                goto err_free;

        rbnode->cache_present = kcalloc(BITS_TO_LONGS(rbnode->blklen),
                                        sizeof(*rbnode->cache_present),
                                        GFP_KERNEL);
        if (!rbnode->cache_present)
                goto err_free_block;

        return rbnode;

err_free_block:
        kfree(rbnode->block);
err_free:
        kfree(rbnode);
        return NULL;
}

static int regcache_rbtree_write(struct regmap *map, unsigned int reg,
                                 unsigned int value)
{
        struct regcache_rbtree_ctx *rbtree_ctx;
        struct regcache_rbtree_node *rbnode, *rbnode_tmp;
        struct rb_node *node;
        unsigned int reg_tmp;
        int ret;

        rbtree_ctx = map->cache;

        /* if we can't locate it in the cached rbnode we'll have
         * to traverse the rbtree looking for it.
         */
        rbnode = regcache_rbtree_lookup(map, reg);
        if (rbnode) {
                reg_tmp = (reg - rbnode->base_reg) / map->reg_stride;
                regcache_rbtree_set_register(map, rbnode, reg_tmp, value);
        } else {
                unsigned int base_reg, top_reg;
                unsigned int new_base_reg, new_top_reg;
                unsigned int min, max;
                unsigned int max_dist;
                unsigned int dist, best_dist = UINT_MAX;

                max_dist = map->reg_stride * sizeof(*rbnode_tmp) /
                        map->cache_word_size;
                if (reg < max_dist)
                        min = 0;
                else
                        min = reg - max_dist;
                max = reg + max_dist;

                /* look for an adjacent register to the one we are about to add */
                node = rbtree_ctx->root.rb_node;
                while (node) {
                        rbnode_tmp = rb_entry(node, struct regcache_rbtree_node,
                                              node);

                        regcache_rbtree_get_base_top_reg(map, rbnode_tmp,
                                &base_reg, &top_reg);

                        if (base_reg <= max && top_reg >= min) {
                                if (reg < base_reg)
                                        dist = base_reg - reg;
                                else if (reg > top_reg)
                                        dist = reg - top_reg;
                                else
                                        dist = 0;
                                if (dist < best_dist) {
                                        rbnode = rbnode_tmp;
                                        best_dist = dist;
                                        new_base_reg = min(reg, base_reg);
                                        new_top_reg = max(reg, top_reg);
                                }
                        }

                        /*
                         * Keep looking, we want to choose the closest block,
                         * otherwise we might end up creating overlapping
                         * blocks, which breaks the rbtree.
                         */
                        if (reg < base_reg)
                                node = node->rb_left;
                        else if (reg > top_reg)
                                node = node->rb_right;
                        else
                                break;
                }

                if (rbnode) {
                        ret = regcache_rbtree_insert_to_block(map, rbnode,
                                                              new_base_reg,
                                                              new_top_reg, reg,
                                                              value);
                        if (ret)
                                return ret;
                        rbtree_ctx->cached_rbnode = rbnode;
                        return 0;
                }

                /* We did not manage to find a place to insert it in
                 * an existing block so create a new rbnode.
                 */
                rbnode = regcache_rbtree_node_alloc(map, reg);
                if (!rbnode)
                        return -ENOMEM;
                regcache_rbtree_set_register(map, rbnode,
                                             reg - rbnode->base_reg, value);
                regcache_rbtree_insert(map, &rbtree_ctx->root, rbnode);
                rbtree_ctx->cached_rbnode = rbnode;
        }

        return 0;
}

static int regcache_rbtree_sync(struct regmap *map, unsigned int min,
                                unsigned int max)
{
        struct regcache_rbtree_ctx *rbtree_ctx;
        struct rb_node *node;
        struct regcache_rbtree_node *rbnode;
        unsigned int base_reg, top_reg;
        unsigned int start, end;
        int ret;

        rbtree_ctx = map->cache;
        for (node = rb_first(&rbtree_ctx->root); node; node = rb_next(node)) {
                rbnode = rb_entry(node, struct regcache_rbtree_node, node);

                regcache_rbtree_get_base_top_reg(map, rbnode, &base_reg,
                        &top_reg);
                if (base_reg > max)
                        break;
                if (top_reg < min)
                        continue;

                if (min > base_reg)
                        start = (min - base_reg) / map->reg_stride;
                else
                        start = 0;

                if (max < top_reg)
                        end = (max - base_reg) / map->reg_stride + 1;
                else
                        end = rbnode->blklen;

                ret = regcache_sync_block(map, rbnode->block,
                                          rbnode->cache_present,
                                          rbnode->base_reg, start, end);
                if (ret != 0)
                        return ret;
        }

        return regmap_async_complete(map);
}

static int regcache_rbtree_drop(struct regmap *map, unsigned int min,
                                unsigned int max)
{
        struct regcache_rbtree_ctx *rbtree_ctx;
        struct regcache_rbtree_node *rbnode;
        struct rb_node *node;
        unsigned int base_reg, top_reg;
        unsigned int start, end;

        rbtree_ctx = map->cache;
        for (node = rb_first(&rbtree_ctx->root); node; node = rb_next(node)) {
                rbnode = rb_entry(node, struct regcache_rbtree_node, node);

                regcache_rbtree_get_base_top_reg(map, rbnode, &base_reg,
                        &top_reg);
                if (base_reg > max)
                        break;
                if (top_reg < min)
                        continue;

                if (min > base_reg)
                        start = (min - base_reg) / map->reg_stride;
                else
                        start = 0;

                if (max < top_reg)
                        end = (max - base_reg) / map->reg_stride + 1;
                else
                        end = rbnode->blklen;

                bitmap_clear(rbnode->cache_present, start, end - start);
        }

        return 0;
}

struct regcache_ops regcache_rbtree_ops = {
        .type = REGCACHE_RBTREE,
        .name = "rbtree",
        .init = regcache_rbtree_init,
        .exit = regcache_rbtree_exit,
#ifdef CONFIG_DEBUG_FS
        .debugfs_init = rbtree_debugfs_init,
#endif
        .read = regcache_rbtree_read,
        .write = regcache_rbtree_write,
        .sync = regcache_rbtree_sync,
        .drop = regcache_rbtree_drop,
};