• Serge Semin's avatar
    gpio: dwapb: Convert driver to using the GPIO-lib-based IRQ-chip · 0ea68393
    Serge Semin authored
    GPIO-lib provides a ready-to-use interface to initialize an IRQ-chip on
    top of a GPIO chip. It's better from maintainability and readability
    point of view to use one instead of supporting a hand-written Generic
    IRQ-chip-based implementation. Moreover the new implementation won't
    cause much functional overhead but will provide a cleaner driver code.
    All of that makes the DW APB GPIO driver conversion pretty much justified
    especially seeing a tendency of the other GPIO drivers getting converted
    too.
    
    Here is what we do in the framework of this commit to convert the driver
    to using the GPIO-lib-based IRQ-chip interface:
    
    1) IRQ ack, mask and unmask callbacks are locally defined instead of
    using the Generic IRQ-chip ones.
    
    2) An irq_chip structure instance is embedded into the dwapb_gpio
    private data. Note we can't have a static instance of that structure since
    GPIO-lib will add some hooks into it by calling gpiochip_set_irq_hooks().
    A warning about that would have been printed by the GPIO-lib code if we
    used a single irq_chip structure instance for multiple DW APB GPIO
    controllers.
    
    3) Initialize the gpio_irq_chip structure embedded into the gpio_chip
    descriptor. By default there is no IRQ enabled so any event raised will be
    handled by the handle_bad_irq() IRQ flow handler. If DW APB GPIO IP-core
    is synthesized to have non-shared reference IRQ-lines, then as before the
    hierarchical and cascaded cases are distinguished by checking how many
    parental IRQs are defined. (Note irq_set_chained_handler_and_data() won't
    initialize IRQs, which descriptors couldn't be found.) If DW APB GPIO IP
    is used on a platform with shared IRQ line, then we simply won't let the
    GPIO-lib to initialize the parental IRQs, but will handle them locally in
    the driver.
    
    4) Discard linear IRQ-domain and Generic IRQ-chip initialization, since
    GPIO-lib IRQ-chip interface will create a new domain and accept a standard
    IRQ-chip structure pointer based on the setting we provided in the
    gpio_irq_chip structure.
    
    5) Manually select a proper IRQ flow handler directly in the
    irq_set_type() callback by calling irq_set_handler_locked() method, since
    an ordinary (not Generic) irq_chip descriptor is now utilized. Note this
    shalln't give any regression
    
    6) Alter CONFIG_GPIO_DWAPB kernel config to select
    CONFIG_GPIOLIB_IRQCHIP instead of CONFIG_GENERIC_IRQ_CHIP.
    
    Note neither 4) nor 5) shall cause a regression of commit 6a2f4b7d
    ("gpio: dwapb: use a second irq chip"), since the later isn't properly
    used here anyway.
    Signed-off-by: default avatarSerge Semin <Sergey.Semin@baikalelectronics.ru>
    Reviewed-by: default avatarAndy Shevchenko <andy.shevchenko@gmail.com>
    Link: https://lore.kernel.org/r/20200730152808.2955-6-Sergey.Semin@baikalelectronics.ruSigned-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
    0ea68393
gpio-dwapb.c 20.6 KB