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| H A D | Kconfig | diff 0ea683931adb27d588fa74c30ac242ed2414e438 Thu Jul 30 17:28:02 CEST 2020 Serge Semin <Sergey.Semin@baikalelectronics.ru> gpio: dwapb: Convert driver to using the GPIO-lib-based IRQ-chip
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 6a2f4b7dadd5
("gpio: dwapb: use a second irq chip"), since the later isn't properly
used here anyway.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20200730152808.2955-6-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
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