linux-kernel - Re: [PATCH 06/13] gpio: add AD24xx GPIO driver

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Date: Tue, 28 May 2024 14:13:02 +0200
From: Linus Walleij <linus.walleij@...aro.org>
To: Alvin Šipraga <alvin@...s.dk>
Cc: Mark Brown <broonie@...nel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	"Rafael J. Wysocki" <rafael@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Bartosz Golaszewski <brgl@...ev.pl>, Liam Girdwood <lgirdwood@...il.com>, Jaroslav Kysela <perex@...ex.cz>, 
	Takashi Iwai <tiwai@...e.com>, Michael Turquette <mturquette@...libre.com>, 
	Stephen Boyd <sboyd@...nel.org>, Andi Shyti <andi.shyti@...nel.org>, 
	Saravana Kannan <saravanak@...gle.com>, Emil Svendsen <emas@...g-olufsen.dk>, 
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-gpio@...r.kernel.org, linux-sound@...r.kernel.org, 
	linux-clk@...r.kernel.org, linux-i2c@...r.kernel.org, 
	Alvin Šipraga <alsi@...g-olufsen.dk>
Subject: Re: [PATCH 06/13] gpio: add AD24xx GPIO driver

Hi Alvin,

thanks for your patch!

On Fri, May 17, 2024 at 2:58 PM Alvin Šipraga <alvin@...s.dk> wrote:

> From: Alvin Šipraga <alsi@...g-olufsen.dk>
>
> This driver adds GPIO function support for AD24xx A2B transceiver chips.
> When a GPIO is requested, the relevant pin is automatically muxed to
> GPIO mode. The device tree property gpio-reserved-ranges can be used to
> protect certain pins which are reserved for other functionality such as
> I2S/TDM data.
>
> Signed-off-by: Alvin Šipraga <alsi@...g-olufsen.dk>
(...)

>  config A2B_AD24XX_NODE
>         tristate "Analog Devices Inc. AD24xx node support"
>         select REGMAP_A2B
> +       imply GPIO_AD24XX

Maybe it should even be select, if it's hard to think about a case
where this is not desired?

> +config GPIO_AD24XX
> +       tristate "Analog Devies Inc. AD24xx GPIO support"
> +       depends on A2B_AD24XX_NODE
> +       help
> +         Say Y here to enable GPIO support for AD24xx A2B transceivers.
> +
>  config GPIO_ARIZONA
>         tristate "Wolfson Microelectronics Arizona class devices"
>         depends on MFD_ARIZONA

This is grouped with the MFD devices but as I understand it A2B is a
completely new bus type? Is MFD even always selected when A2B is
in use?

To me it's fine to add a new submenu for A2B devices, if there will be
more of them.

> +static int ad24xx_gpio_get_direction(struct gpio_chip *gc, unsigned int offset)
> +{
> +       struct ad24xx_gpio *adg = gpiochip_get_data(gc);
> +       unsigned int val;
> +       int ret;
> +
> +       ret = regmap_read(adg->regmap, A2B_GPIOOEN, &val);
> +       if (ret)
> +               return ret;
> +
> +       if (val & BIT(offset))
> +               return 0; /* output */
> +
> +       return 1; /* input */

Please use GPIO_LINE_DIRECTION_OUT/GPIO_LINE_DIRECTION_IN
instead of 0/1 here?

Then you don't need the comments because it's evident.

> +static int ad24xx_gpio_get(struct gpio_chip *gc, unsigned int offset)
> +{
> +       struct ad24xx_gpio *adg = gpiochip_get_data(gc);
> +       unsigned int val;
> +       int ret;
> +
> +       ret = regmap_read(adg->regmap, A2B_GPIOIN, &val);
> +       if (ret)
> +               return ret;
> +
> +       if (val & BIT(offset))
> +               return 1; /* high */
> +
> +       return 0; /* low */

Just

return !!(val & BIT(offset));

> +static int ad24xx_gpio_child_to_parent_hwirq(struct gpio_chip *gc,
> +                                            unsigned int child,
> +                                            unsigned int child_type,
> +                                            unsigned int *parent,
> +                                            unsigned int *parent_type)
> +{
> +       *parent = child;
> +       return 0;
> +}

This deserves a comment, is IRQ 0 the singular parent of
everything? Then it doesn't seem very hierarchical but rather
cascaded don't you think?

> +static int ad24xx_gpio_irq_set_type(struct irq_data *d, unsigned int type)
> +{
> +       struct gpio_chip *gpio_chip = irq_data_get_irq_chip_data(d);
> +       struct ad24xx_gpio *adg = gpiochip_get_data(gpio_chip);
> +       irq_hw_number_t hwirq = irqd_to_hwirq(d);
> +
> +       switch (type) {
> +       case IRQ_TYPE_EDGE_RISING:
> +               adg->irq_invert &= ~BIT(hwirq);
> +               break;
> +       case IRQ_TYPE_EDGE_FALLING:
> +               adg->irq_invert |= BIT(hwirq);
> +               break;
> +       default:
> +               return -EINVAL;
> +       }

No need for the "toggling trick" for supporting IRQ on both edges?
Implementing that hack (which is in several drivers) will be nice to
have for e.g. pushbuttons.

> +static void ad24xx_gpio_irq_bus_lock(struct irq_data *d)
> +{
> +       struct gpio_chip *gpio_chip = irq_data_get_irq_chip_data(d);
> +       struct ad24xx_gpio *adg = gpiochip_get_data(gpio_chip);
> +
> +       mutex_lock(&adg->mutex);
> +}

Is this mutex needed since there is already a mutex or spinlock
in the regmap? Isn't this the case for A2B?

Yours,
Linus Walleij