On Thu, Jul 30, 2020 at 05:26:18PM +0300, Andy Shevchenko wrote:
> On Thu, Jul 30, 2020 at 04:55:31PM +0300, Serge Semin wrote:
> > 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.
>
> Easy to read if you put blank lines in between of items.
Ok.
>
> > 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.
>
> ...
>
> > struct dwapb_gpio_port {
> > struct gpio_chip gc;
> > + unsigned int nr_irqs;
> > + unsigned int irq[DWAPB_MAX_GPIOS];
> > + struct irq_chip irqchip;
> > bool is_registered;
> > struct dwapb_gpio *gpio;
>
> Isn't it too much wasted memory (imagine 4 port controller)?
>
> What if we have it in another structure and allocate dynamically?
>
> struct dwapb_gpio_port_irqchip {
> struct irq_chip irqchip;
> unsigned int nr_irqs;
> unsigned int irq[DWAPB_MAX_GPIOS];
> };
Agree. I have to send a new revision of the series anyway. I'll do that shortly.
-Sergey
>
> ...
> struct dwapb_gpio_port_irqchip *pirq;
> ...
>
> (I agree that IRQ chip is rather property of a port than controller)
>
> --
> With Best Regards,
> Andy Shevchenko
>
>
