On Thu, Jul 23, 2020 at 05:08:15PM +0300, Andy Shevchenko wrote:

On Thu, Jul 23, 2020 at 04:38:55AM +0300, Serge Semin wrote:

quoted

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.
6) Discard the custom GPIO-to-IRQ mapping function since GPIO-lib defines
the standard method gpiochip_to_irq(), which will be used anyway no matter
whether the custom to_irq callback is specified or not.
7) Discard the acpi_gpiochip_{request,free}_interrupts()
invocations, since they will be called from
gpiochip_add_irqchip()/gpiochip_irqchip_remove() anyway.
8) Alter CONFIG_GPIO_DWAPB kernel config to select
CONFIG_GPIOLIB_IRQCHIP instead of CONFIG_GENERIC_IRQ_CHIP.

...

One more thing...

quoted

 static u32 dwapb_do_irq(struct dwapb_gpio *gpio)
 {
+	struct gpio_chip *gc = &gpio->ports[0].gc;
 	unsigned long irq_status;
 	irq_hw_number_t hwirq;
 
 	irq_status = dwapb_read(gpio, GPIO_INTSTATUS);
 	for_each_set_bit(hwirq, &irq_status, 32) {
-		int gpio_irq = irq_find_mapping(gpio->domain, hwirq);
+		int gpio_irq = gc->to_irq(gc, hwirq);

Very, very few do this.
Can we stick with the original one?
(See plenty of other examples in the GPIO / pin control subsystems.

You are right. After more thorough studying the IRQ-domain code I've found out
that irq_domain_add_simple() provides the on-the-fly mapping creation. We
don't have to call irq_create_mapping() first before using irq_find_mapping().
So the irq_find_mapping(gc->irq.domain, hwirq) method can be freely called here
the same way as the most of the GPIO drivers do. Thanks for noticing this.

-Sergey

quoted

 		u32 irq_type = irq_get_trigger_type(gpio_irq);
 
 		generic_handle_irq(gpio_irq);

quoted

 }

-- 
With Best Regards,
Andy Shevchenko