• Simon Glass's avatar
    dm: Allow drivers to be marked 'before relocation' · 00606d7e
    Simon Glass authored
    
    
    Driver model currently only operates after relocation is complete. In this
    state U-Boot typically has a small amount of memory available. In adding
    support for driver model prior to relocation we must try to use as little
    memory as possible.
    
    In addition, on some machines the memory has not be inited and/or the CPU
    is not running at full speed or the data cache is off. These can reduce
    execution performance, so the less initialisation that is done before
    relocation the better.
    
    An immediately-obvious improvement is to only initialise drivers which are
    actually going to be used before relocation. On many boards the only such
    driver is a serial UART, so this provides a very large potential benefit.
    
    Allow drivers to mark themselves as 'pre-reloc' which means that they will
    be initialised prior to relocation. This can be done either with a driver
    flag or with a 'dm,pre-reloc' device tree property.
    
    To support this, the various dm scanning function now take a 'pre_reloc_only'
    parameter which indicates that only drivers marked pre-reloc should be
    bound.
    
    Signed-off-by: default avatarSimon Glass <sjg@chromium.org>
    00606d7e