Linux-GPIO Archive on lore.kernel.org
 help / color / Atom feed
From: Serge Semin <Sergey.Semin@baikalelectronics.ru>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Serge Semin <fancer.lancer@gmail.com>,
	Hoan Tran <hoan@os.amperecomputing.com>,
	Linus Walleij <linus.walleij@linaro.org>,
	Bartosz Golaszewski <bgolaszewski@baylibre.com>,
	Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>,
	Pavel Parkhomenko <Pavel.Parkhomenko@baikalelectronics.ru>,
	Rob Herring <robh+dt@kernel.org>, <linux-gpio@vger.kernel.org>,
	<devicetree@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 05/10] gpio: dwapb: Convert driver to using the GPIO-lib-based IRQ-chip
Date: Thu, 30 Jul 2020 17:38:20 +0300
Message-ID: <20200730143820.suneapi2ilp34nat@mobilestation> (raw)
In-Reply-To: <20200730142618.GM3703480@smile.fi.intel.com>

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
> 
> 

  reply index

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-30 13:55 [PATCH v2 00/10] gpio: dwapb: Refactor GPIO resources initialization Serge Semin
2020-07-30 13:55 ` [PATCH v2 01/10] dt-bindings: gpio: dwapb: Add ngpios property support Serge Semin
2020-07-30 13:55 ` [PATCH v2 02/10] gpio: dwapb: Add ngpios DT-property support Serge Semin
2020-07-30 13:55 ` [PATCH v2 03/10] gpio: dwapb: Move MFD-specific IRQ handler Serge Semin
2020-07-30 13:55 ` [PATCH v2 04/10] gpio: dwapb: Add max GPIOs macro Serge Semin
2020-07-30 14:05   ` Andy Shevchenko
2020-07-30 14:07     ` Serge Semin
2020-07-30 14:25     ` Serge Semin
2020-07-30 13:55 ` [PATCH v2 05/10] gpio: dwapb: Convert driver to using the GPIO-lib-based IRQ-chip Serge Semin
2020-07-30 14:26   ` Andy Shevchenko
2020-07-30 14:38     ` Serge Semin [this message]
2020-07-30 13:55 ` [PATCH v2 06/10] gpio: dwapb: Discard GPIO-to-IRQ mapping function Serge Semin
2020-07-30 14:26   ` Andy Shevchenko
2020-07-30 13:55 ` [PATCH v2 07/10] gpio: dwapb: Discard ACPI GPIO-chip IRQs request Serge Semin
2020-07-30 14:27   ` Andy Shevchenko
2020-07-30 13:55 ` [PATCH v2 08/10] gpio: dwapb: Get reset control by means of resource managed interface Serge Semin
2020-07-30 13:55 ` [PATCH v2 09/10] gpio: dwapb: Get clocks " Serge Semin
2020-07-30 13:55 ` [PATCH v2 10/10] gpio: dwapb: Use resource managed GPIO-chip add data method Serge Semin
2020-07-30 14:16 ` [PATCH v2 00/10] gpio: dwapb: Refactor GPIO resources initialization Serge Semin

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200730143820.suneapi2ilp34nat@mobilestation \
    --to=sergey.semin@baikalelectronics.ru \
    --cc=Alexey.Malahov@baikalelectronics.ru \
    --cc=Pavel.Parkhomenko@baikalelectronics.ru \
    --cc=andy.shevchenko@gmail.com \
    --cc=bgolaszewski@baylibre.com \
    --cc=devicetree@vger.kernel.org \
    --cc=fancer.lancer@gmail.com \
    --cc=hoan@os.amperecomputing.com \
    --cc=linus.walleij@linaro.org \
    --cc=linux-gpio@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=robh+dt@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-GPIO Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-gpio/0 linux-gpio/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-gpio linux-gpio/ https://lore.kernel.org/linux-gpio \
		linux-gpio@vger.kernel.org
	public-inbox-index linux-gpio

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-gpio


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git