Re: [PATCH v3 1/3] gpio: gpio-regmap: add flags to control some behaviour

[Bjorn Helgaas <helgaas@kernel.org>]

Not my area, but consider making the subject more specific, e.g.,
"add flag to set direction before value"

On Thu, Aug 21, 2025 at 12:18:57PM +0200, Marcos Del Sol Vives wrote:
> The Vortex86 family of SoCs need the direction set before the value, else
> writes to the DATA ports are ignored.
> 
> This commit adds a new "flags" field plus a flag to change the default
> behaviour, which is to set first the direction and then the value.

This sounds like the default behavior is to set direction, then value.
But from the patch, it looks like:

  - default: set value, then direction

  - with GPIO_REGMAP_DIR_BEFORE_SET: set direction, then value

> Signed-off-by: Marcos Del Sol Vives <marcos@orca.pet>
> ---
>  drivers/gpio/gpio-regmap.c  | 17 ++++++++++++++++-
>  include/linux/gpio/regmap.h | 17 +++++++++++++++++
>  2 files changed, 33 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpio/gpio-regmap.c b/drivers/gpio/gpio-regmap.c
> index e8a32dfebdcb..24cefbd57637 100644
> --- a/drivers/gpio/gpio-regmap.c
> +++ b/drivers/gpio/gpio-regmap.c
> @@ -31,6 +31,7 @@ struct gpio_regmap {
>  	unsigned int reg_clr_base;
>  	unsigned int reg_dir_in_base;
>  	unsigned int reg_dir_out_base;
> +	unsigned int flags;
>  
>  	int (*reg_mask_xlate)(struct gpio_regmap *gpio, unsigned int base,
>  			      unsigned int offset, unsigned int *reg,
> @@ -196,7 +197,20 @@ static int gpio_regmap_direction_input(struct gpio_chip *chip,
>  static int gpio_regmap_direction_output(struct gpio_chip *chip,
>  					unsigned int offset, int value)
>  {
> -	gpio_regmap_set(chip, offset, value);
> +	struct gpio_regmap *gpio = gpiochip_get_data(chip);
> +	int ret;
> +
> +	if (gpio->flags & GPIO_REGMAP_DIR_BEFORE_SET) {
> +		ret = gpio_regmap_set_direction(chip, offset, true);
> +		if (ret)
> +			return ret;
> +
> +		return gpio_regmap_set(chip, offset, value);
> +	}
> +
> +	ret = gpio_regmap_set(chip, offset, value);
> +	if (ret)
> +		return ret;
>  
>  	return gpio_regmap_set_direction(chip, offset, true);
>  }
> @@ -247,6 +261,7 @@ struct gpio_regmap *gpio_regmap_register(const struct gpio_regmap_config *config
>  	gpio->reg_clr_base = config->reg_clr_base;
>  	gpio->reg_dir_in_base = config->reg_dir_in_base;
>  	gpio->reg_dir_out_base = config->reg_dir_out_base;
> +	gpio->flags = config->flags;
>  
>  	chip = &gpio->gpio_chip;
>  	chip->parent = config->parent;
> diff --git a/include/linux/gpio/regmap.h b/include/linux/gpio/regmap.h
> index c722c67668c6..aea107e71fec 100644
> --- a/include/linux/gpio/regmap.h
> +++ b/include/linux/gpio/regmap.h
> @@ -12,6 +12,20 @@ struct regmap;
>  #define GPIO_REGMAP_ADDR_ZERO ((unsigned int)(-1))
>  #define GPIO_REGMAP_ADDR(addr) ((addr) ? : GPIO_REGMAP_ADDR_ZERO)
>  
> +
> +/**
> + * enum gpio_regmap_flags - flags to control GPIO operation
> + */
> +enum gpio_regmap_flags {
> +	/**
> +	 * @GPIO_REGMAP_DIR_BEFORE_SET: when setting a pin as an output, set
> +	 * its direction before the value. The output value will be undefined
> +	 * for a short time which may have unwanted side effects, but some
> +	 * hardware requires this.
> +	 */
> +	GPIO_REGMAP_DIR_BEFORE_SET	= BIT(0),
> +};
> +
>  /**
>   * struct gpio_regmap_config - Description of a generic regmap gpio_chip.
>   * @parent:		The parent device
> @@ -23,6 +37,8 @@ struct regmap;
>   *			If not given, the name of the device is used.
>   * @ngpio:		(Optional) Number of GPIOs
>   * @names:		(Optional) Array of names for gpios
> + * @flags:		(Optional) A bitmask of flags from
> + * 			&enum gpio_regmap_flags
>   * @reg_dat_base:	(Optional) (in) register base address
>   * @reg_set_base:	(Optional) set register base address
>   * @reg_clr_base:	(Optional) clear register base address
> @@ -68,6 +84,7 @@ struct gpio_regmap_config {
>  	const char *label;
>  	int ngpio;
>  	const char *const *names;
> +	unsigned int flags;
>  
>  	unsigned int reg_dat_base;
>  	unsigned int reg_set_base;
> -- 
> 2.34.1
>