• Masahiro Yamada's avatar
    pinctrl: add pin control uclass support · d90a5a30
    Masahiro Yamada authored
    This creates a new framework for handling of pin control devices,
    i.e. devices that control different aspects of package pins.
    
    This uclass handles pinmuxing and pin configuration; pinmuxing
    controls switching among silicon blocks that share certain physical
    pins, pin configuration handles electronic properties such as pin-
    biasing, load capacitance etc.
    
    This framework can support the same device tree bindings, but if you
    do not need full interface support, you can disable some features to
    reduce memory foot print.  Typically around 1.5KB is necessary to
    include full-featured uclass support on ARM board (CONFIG_PINCTRL +
    CONFIG_PINCTRL_FULL + CONFIG_PINCTRL_GENERIC + CONFIG_PINCTRL_PINMUX),
    for example.
    
    We are often limited on code size for SPL.  Besides, we still have
    many boards that do not support device tree configuration.  The full
    pinctrl, which requires OF_CONTROL, does not make sense for those
    boards.  So, this framework also has a Do-It-Yourself (let's say
    simple pinctrl) interface.  With CONFIG_PINCTRL_FULL disabled, the
    uclass itself provides no systematic mechanism for identifying the
    peripheral device, applying pinctrl settings, etc.  They must be
    done in each low-level driver.  In return, you can save much memory
    footprint and it might be useful especially for SPL.
    Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
    Acked-by: default avatarSimon Glass <sjg@chromium.org>
    d90a5a30
pinctrl-generic.c 9.16 KB