regcache-rbtree.c

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/*
 * Register cache access API - rbtree caching support
 *
 * Copyright 2011 Wolfson Microelectronics plc
 *
 * Author: Dimitris Papastamos <[email protected]>
 *
 * 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/slab.h>
#include <linux/device.h>
#include <linux/debugfs.h>
#include <linux/rbtree.h>
#include <linux/seq_file.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 {
    /* the actual rbtree node holding this block */
    struct rb_node node;
    /* base register handled by this block */
    unsigned int base_reg;
    /* block of adjacent registers */
    void *block;
    /* number of registers available in the block */
    unsigned int blklen;
} __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 regcache_rbtree_node *rbnode, unsigned int idx,
    unsigned int word_size)
{
    return regcache_get_val(rbnode->block, idx, word_size);
}

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

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 = container_of(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 = container_of(*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;
    int nodes = 0;
    int registers = 0;
    int this_registers, average;

    map->lock(map);

    for (node = rb_first(&rbtree_ctx->root); node != NULL;
         node = rb_next(node)) {
        n = container_of(node, struct regcache_rbtree_node, node);

        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\n",
           nodes, registers, average);

    map->unlock(map);

    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);
}
#else
static void rbtree_debugfs_init(struct regmap *map)
{
}
#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;
    }

    rbtree_debugfs_init(map);

    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->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;
        *value = regcache_rbtree_get_register(rbnode, reg_tmp,
                              map->cache_word_size);
    } else {
        return -ENOENT;
    }

    return 0;
}


static int regcache_rbtree_insert_to_block(struct regcache_rbtree_node *rbnode,
                       unsigned int pos, unsigned int reg,
                       unsigned int value, unsigned int word_size)
{
    u8 *blk;

    blk = krealloc(rbnode->block,
               (rbnode->blklen + 1) * word_size, GFP_KERNEL);
    if (!blk)
        return -ENOMEM;

    /* insert the register value in the correct place in the rbnode block */
    memmove(blk + (pos + 1) * word_size,
        blk + pos * word_size,
        (rbnode->blklen - pos) * word_size);

    /* update the rbnode block, its size and the base register */
    rbnode->block = blk;
    rbnode->blklen++;
    if (!pos)
        rbnode->base_reg = reg;

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

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 val;
    unsigned int reg_tmp;
    unsigned int pos;
    int i;
    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;
        val = regcache_rbtree_get_register(rbnode, reg_tmp,
                           map->cache_word_size);
        if (val == value)
            return 0;
        regcache_rbtree_set_register(rbnode, reg_tmp, value,
                         map->cache_word_size);
    } else {
        /* look for an adjacent register to the one we are about to add */
        for (node = rb_first(&rbtree_ctx->root); node;
             node = rb_next(node)) {
            rbnode_tmp = rb_entry(node, struct regcache_rbtree_node,
                          node);
            for (i = 0; i < rbnode_tmp->blklen; i++) {
                reg_tmp = rbnode_tmp->base_reg +
                        (i * map->reg_stride);
                if (abs(reg_tmp - reg) != map->reg_stride)
                    continue;
                /* decide where in the block to place our register */
                if (reg_tmp + map->reg_stride == reg)
                    pos = i + 1;
                else
                    pos = i;
                ret = regcache_rbtree_insert_to_block(rbnode_tmp, pos,
                                      reg, value,
                                      map->cache_word_size);
                if (ret)
                    return ret;
                rbtree_ctx->cached_rbnode = rbnode_tmp;
                return 0;
            }
        }
        /* we did not manage to find a place to insert it in an existing
         * block so create a new rbnode with a single register in its block.
         * This block will get populated further if any other adjacent
         * registers get modified in the future.
         */
        rbnode = kzalloc(sizeof *rbnode, GFP_KERNEL);
        if (!rbnode)
            return -ENOMEM;
        rbnode->blklen = 1;
        rbnode->base_reg = reg;
        rbnode->block = kmalloc(rbnode->blklen * map->cache_word_size,
                    GFP_KERNEL);
        if (!rbnode->block) {
            kfree(rbnode);
            return -ENOMEM;
        }
        regcache_rbtree_set_register(rbnode, 0, value, map->cache_word_size);
        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 regtmp;
    unsigned int val;
    int ret;
    int i, base, 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);

        if (rbnode->base_reg < min)
            continue;
        if (rbnode->base_reg > max)
            break;
        if (rbnode->base_reg + rbnode->blklen < min)
            continue;

        if (min > rbnode->base_reg)
            base = min - rbnode->base_reg;
        else
            base = 0;

        if (max < rbnode->base_reg + rbnode->blklen)
            end = rbnode->base_reg + rbnode->blklen - max;
        else
            end = rbnode->blklen;

        for (i = base; i < end; i++) {
            regtmp = rbnode->base_reg + (i * map->reg_stride);
            val = regcache_rbtree_get_register(rbnode, i,
                               map->cache_word_size);

            /* Is this the hardware default?  If so skip. */
            ret = regcache_lookup_reg(map, regtmp);
            if (ret >= 0 && val == map->reg_defaults[ret].def)
                continue;

            map->cache_bypass = 1;
            ret = _regmap_write(map, regtmp, val);
            map->cache_bypass = 0;
            if (ret)
                return ret;
            dev_dbg(map->dev, "Synced register %#x, value %#x\n",
                regtmp, val);
        }
    }

    return 0;
}

struct regcache_ops regcache_rbtree_ops = {
    .type = REGCACHE_RBTREE,
    .name = "rbtree",
    .init = regcache_rbtree_init,
    .exit = regcache_rbtree_exit,
    .read = regcache_rbtree_read,
    .write = regcache_rbtree_write,
    .sync = regcache_rbtree_sync
};