[PATCH 1/2] ASoC: soc-cache: block based rbtree compression

    This patch prepares the ground for the actual rbtree optimization patch
    which will save a pointer to the last accessed rbnode that was used
    in either the read() or write() functions.

    Each rbnode manages a variable length block of registers.  There can be no
    two nodes with overlapping blocks.  Each block has a base register and a
    currently top register, all the other registers, if any, lie in between these
    two and in ascending order.

    The reasoning behind the construction of this rbtree is simple.  In the
    snd_soc_rbtree_cache_init() function, we iterate over the register defaults
    provided by the driver.  For each register value that is non-zero we
    insert it in the rbtree.  In order to determine in which rbnode we need
    to add the register, we first look if there is another register already
    added that is adjacent to the one we are about to add.  If that is the case
    we append it in that rbnode block, otherwise we create a new rbnode
    with a single register in its block and add it to the tree.

    In the next patch, where a cached rbnode is used by both the write() and the
    read() functions, we also check if the register we are about to add is in the
    cached rbnode (the least recently accessed one) and if so we append it in that
    rbnode block.

    Signed-off-by: Dimitris Papastamos <dp@opensource.wolfsonmicro.com>
    Acked-by: Liam Girdwood <lrg@ti.com>
    Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
[PATCH 2/2] ASoC: soc-cache: cache a pointer to the last accessed rbtree block

    Whenever we are doing a read or a write through the rbtree code, we'll
    cache a pointer to the rbnode.  To avoid looking up the register
    everytime we do a read or a write, we first check if it can be found in
    the cached register block, otherwise we traverse the rbtree and finally
    cache the rbnode for future use.

    Signed-off-by: Dimitris Papastamos <dp@opensource.wolfsonmicro.com>
    Acked-by: Liam Girdwood <lrg@ti.com>
    Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>