linux-kernel - Re: [PATCH v4 07/10] gpio: max7360: Add MAX7360 gpio support

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Message-ID: <Z9PlYSZDviGOCV7X@surfacebook.localdomain>
Date: Fri, 14 Mar 2025 10:14:25 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Mathieu Dubois-Briand <mathieu.dubois-briand@...tlin.com>
Cc: Andy Shevchenko <andriy.shevchenko@...el.com>,
	Lee Jones <lee@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Kamel Bouhara <kamel.bouhara@...tlin.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Bartosz Golaszewski <brgl@...ev.pl>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Uwe Kleine-König <ukleinek@...nel.org>,
	Michael Walle <mwalle@...nel.org>, Mark Brown <broonie@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...nel.org>, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
	linux-input@...r.kernel.org, linux-pwm@...r.kernel.org,
	Grégory Clement <gregory.clement@...tlin.com>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v4 07/10] gpio: max7360: Add MAX7360 gpio support

Thu, Mar 13, 2025 at 06:07:03PM +0100, Mathieu Dubois-Briand kirjoitti:
> On Fri Feb 14, 2025 at 4:59 PM CET, Andy Shevchenko wrote:
> > On Fri, Feb 14, 2025 at 12:49:57PM +0100, Mathieu Dubois-Briand wrote:
> > > Add driver for Maxim Integrated MAX7360 GPIO/GPO controller.

...

> > > +	/*
> > > +	 * MAX7360_REG_DEBOUNCE contains configuration both for keypad debounce
> > > +	 * timings and gpos/keypad columns repartition. Only the later is
> > > +	 * modified here.
> > > +	 */
> > > +	val = FIELD_PREP(MAX7360_PORTS, ngpios);
> > > +	ret = regmap_write_bits(regmap, MAX7360_REG_DEBOUNCE, MAX7360_PORTS, val);
> > > +	if (ret) {
> > > +		dev_err(dev, "Failed to write max7360 columns/gpos configuration");
> > > +		return ret;
> > > +	}
> >
> > Shouldn't this be configured via ->set_config() callback?
> 
> I believe this comment has been a bit outdated by our discussion on
> using GPIO valid mask, but I believe we could not use the ->set_config()
> callback here: this callback is made to configure a single pin while the
> gpos/keypad columns repartition is global.

Yeah, we have similar desing in Intel Bay Trail (see pinctrl-baytrail.c) and it
requires some software driven heuristics on how individual setting may affect
the global one. But the Q here is is the debounce affects only keypad? Then it
should be configured via keypad matrix driver. Btw, have you checked
drivers/input/keyboard/matrix_keypad.c? Is there anything that can be useful
here?

...

> > > +		if (irq < 0)
> > > +			return dev_err_probe(dev, irq, "Failed to get IRQ\n");
> > > +
> > > +		irq_chip = devm_kzalloc(dev, sizeof(*irq_chip), GFP_KERNEL);
> > > +		if (!irq_chip)
> > > +			return -ENOMEM;
> > > +
> > > +		irq_chip->name = dev_name(dev);
> > > +		irq_chip->status_base = MAX7360_REG_GPIOIN;
> > > +		irq_chip->num_regs = 1;
> > > +		irq_chip->num_irqs = MAX7360_MAX_GPIO;
> > > +		irq_chip->irqs = max7360_regmap_irqs;
> > > +		irq_chip->handle_mask_sync = max7360_handle_mask_sync;
> > > +		irq_chip->status_is_level = true;
> > > +		irq_chip->irq_drv_data = regmap;
> > > +
> > > +		for (unsigned int i = 0; i < MAX7360_MAX_GPIO; i++) {
> > > +			regmap_write_bits(regmap, MAX7360_REG_PWMCFG(i),
> > > +					  MAX7360_PORT_CFG_INTERRUPT_EDGES,
> > > +					  MAX7360_PORT_CFG_INTERRUPT_EDGES);
> > > +		}
> > > +
> > > +		flags = IRQF_TRIGGER_LOW | IRQF_ONESHOT | IRQF_SHARED;
> > > +		ret = devm_regmap_add_irq_chip_fwnode(dev, dev_fwnode(dev), regmap, irq, flags, 0,
> > > +						      irq_chip, &irq_chip_data);
> >
> > Right.
> >
> > What I mean in previous discussion is to update gpio-regmap to call this from inside.
> > You need to add irq_chip pointer and irq_chip_data pointer to the regmap configuration
> > and if they are set (or the first one, I dunno if this is supported by IRQ chip core)
> > call this function and assign domain. This should be called after GPIO chip is
> > added, but before IRQ domain attachment.
> >
> 
> Ok, this is a bit more clear to me now. So I came up with something, it
> will be part of the next iteration, probably during the next week.
> 
> This required to add a few additional fields to the gpio_regmap_config
> structure, specifying the IRQ configuration:
> 
> + * @regmap_irq_chip:   (Optional) Pointer on an regmap_irq_chip structure. If
> + *                     set, a regmap-irq device will be created and the IRQ
> + *                     domain will be set accordingly.
> + * @regmap_irq_chip_data: (Optional) Pointer on an regmap_irq_chip_data
> + *                      structure pointer. If set, it will be populated with a
> + *                      pointer on allocated regmap_irq data.
> + * @regmap_irq_irqno   (Optional) The IRQ the device uses to signal interrupts.
> + * @regmap_irq_flags   (Optional) The IRQF_ flags to use for the interrupt.

Okay, just make sure it's guarded by the same ifdeffery as the similar in the
GPIO:

#ifdef CONFIG_GPIOLIB_IRQCHIP

...

> > > +
> > > +		regmap_write(regmap, MAX7360_REG_GPIOOUTM, outconf);
> > > +	}
> > > +
> > > +	/* Add gpio device. */
> > > +	gpio_config.parent = dev;
> > > +	gpio_config.regmap = regmap;
> >
> > > +	if (gpio_function == MAX7360_GPIO_PORT) {
> > > +		gpio_config.ngpio = MAX7360_MAX_GPIO;
> >
> > Why this case can't be managed also via ngpios property? Maybe at the end of
> > the day you rather need to have another property to tell where the split is?
> >
> > This will help a lot and removes unneeded sharing of ngpios here and there.
> >
> > What I read from this code is like you are trying to put _two_in_one_ semantics
> > on the shoulders of "ngpios".
> 
> So as I reworked the keypad columns GPIOs, PORT GPIOs and the COL GPIOs
> are a bit more similar on this point. So far I now use a constant value
> assigned in the driver for both, as I believe there is no way the number
> of GPIOs could be a different. Yet I can easily switch back to a value
> provided by a device property.

Sounds good as long as ngpios is not overloaded with the additional meanings.

-- 
With Best Regards,
Andy Shevchenko