linux-kernel - Re: [PATCH v2 2/7] gpio: regmap: Add configurable dir/value order

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Date:   Tue, 18 May 2021 10:39:20 +0200
From:   Michael Walle <michael@...le.cc>
To:     Sander Vanheule <sander@...nheule.net>
Cc:     Pavel Machek <pavel@....cz>, Rob Herring <robh+dt@...nel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Mark Brown <broonie@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        linux-leds@...r.kernel.org, devicetree@...r.kernel.org,
        linux-gpio@...r.kernel.org, Andrew Lunn <andrew@...n.ch>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/7] gpio: regmap: Add configurable dir/value order

Hi,

Am 2021-05-17 21:28, schrieb Sander Vanheule:
> GPIO chips may not support setting the output value when a pin is
> configured as an input, although the current implementation assumes 
> this
> is always possible.
> 
> Add support for setting pin direction before value. The order defaults
> to setting the value first, but this can be reversed by setting the
> regmap_config.no_set_on_input flag, similar to the corresponding flag 
> in
> the gpio-mmio driver.
> 
> Signed-off-by: Sander Vanheule <sander@...nheule.net>
> ---
>  drivers/gpio/gpio-regmap.c  | 20 +++++++++++++++++---
>  include/linux/gpio/regmap.h |  3 +++
>  2 files changed, 20 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpio/gpio-regmap.c b/drivers/gpio/gpio-regmap.c
> index 134cedf151a7..1cdb20f8f8b4 100644
> --- a/drivers/gpio/gpio-regmap.c
> +++ b/drivers/gpio/gpio-regmap.c
> @@ -170,14 +170,25 @@ static int gpio_regmap_direction_input(struct
> gpio_chip *chip,
>  	return gpio_regmap_set_direction(chip, offset, false);
>  }
> 
> -static int gpio_regmap_direction_output(struct gpio_chip *chip,
> -					unsigned int offset, int value)
> +static int gpio_regmap_dir_out_val_first(struct gpio_chip *chip,
> +					 unsigned int offset, int value)

Can we leave the name as is? TBH I find these two similar names
super confusing. Maybe its just me, though.

>  {
>  	gpio_regmap_set(chip, offset, value);
> 
>  	return gpio_regmap_set_direction(chip, offset, true);
>  }
> 
> +static int gpio_regmap_dir_out_dir_first(struct gpio_chip *chip,
> +					 unsigned int offset, int value)
> +{
> +	int err;

use ret for consistency here

> +
> +	err = gpio_regmap_set_direction(chip, offset, true);
> +	gpio_regmap_set(chip, offset, value);
> +
> +	return err;
> +}
> +

Instead of adding a new one, we can also just check no_set_on_input
in gpio_regmap_direction_output(), which I'd prefer.

static int gpio_regmap_direction_output(struct gpio_chip *chip,
					unsigned int offset, int value)
{
	struct gpio_regmap *gpio = gpiochip_get_data(chip);
	int ret;

	if (gpio->no_set_on_input) {
		/* some smart comment here, also mention gliches */
		ret = gpio_regmap_set_direction(chip, offset, true);
		gpio_regmap_set(chip, offset, value);
	} else {
		gpio_regmap_set(chip, offset, value);
		ret = gpio_regmap_set_direction(chip, offset, true);
	}

	return ret;
}

>  void gpio_regmap_set_drvdata(struct gpio_regmap *gpio, void *data)
>  {
>  	gpio->driver_data = data;
> @@ -277,7 +288,10 @@ struct gpio_regmap *gpio_regmap_register(const
> struct gpio_regmap_config *config
>  	if (gpio->reg_dir_in_base || gpio->reg_dir_out_base) {
>  		chip->get_direction = gio_regmap_get_direction;
>  		chip->direction_input = gpio_regmap_direction_input;
> -		chip->direction_output = gpio_regmap_direction_output;
> +		if (config->no_set_on_input)
> +			chip->direction_output = gpio_regmap_dir_out_dir_first;
> +		else
> +			chip->direction_output = gpio_regmap_dir_out_val_first;
>  	}
> 
>  	ret = gpiochip_add_data(chip, gpio);
> diff --git a/include/linux/gpio/regmap.h b/include/linux/gpio/regmap.h
> index 334dd928042b..2a732f8f23be 100644
> --- a/include/linux/gpio/regmap.h
> +++ b/include/linux/gpio/regmap.h
> @@ -30,6 +30,8 @@ struct regmap;
>   * @reg_dir_out_base:	(Optional) out setting register base address
>   * @reg_stride:		(Optional) May be set if the registers (of the
>   *			same type, dat, set, etc) are not consecutive.
> + * @no_set_on_input:	Set if output value can only be set when the 
> direction
> + *			is configured as output.

set_direction_first ?

>   * @ngpio_per_reg:	Number of GPIOs per register
>   * @irq_domain:		(Optional) IRQ domain if the controller is
>   *			interrupt-capable
> @@ -73,6 +75,7 @@ struct gpio_regmap_config {
>  	unsigned int reg_dir_out_base;
>  	int reg_stride;
>  	int ngpio_per_reg;
> +	bool no_set_on_input;
>  	struct irq_domain *irq_domain;
> 
>  	int (*reg_mask_xlate)(struct gpio_regmap *gpio, unsigned int base,

-michael