Re: [PATCH v3 6/9] gpio: i8255: Migrate to gpio-regmap API

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Tue, Nov 22, 2022 at 02:11:03AM -0500, William Breathitt Gray wrote:
> The regmap API supports IO port accessors so we can take advantage of
> regmap abstractions rather than handling access to the device registers
> directly in the driver.
> 
> By leveraging the gpio-regmap API, the i8255 library is reduced to
> simply a devm_i8255_regmap_register() function, a configuration
> structure struct i8255_regmap_config, and a helper macro
> i8255_volatile_regmap_range() provided to simplify volatile PPI register
> hinting for the regmap.
> 
> Legacy functions and code will be removed once all consumers have
> migrated to the new i8255 library interface.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

(See one remark below and once comment to address)

> Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Signed-off-by: William Breathitt Gray <william.gray@linaro.org>
> ---
>  drivers/gpio/Kconfig      |   1 +
>  drivers/gpio/gpio-i8255.c | 119 ++++++++++++++++++++++++++++++++++----
>  drivers/gpio/gpio-i8255.h |  27 +++++++++
>  3 files changed, 135 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
> index dd34039fc31b..88dfdc62992f 100644
> --- a/drivers/gpio/Kconfig
> +++ b/drivers/gpio/Kconfig
> @@ -831,6 +831,7 @@ menu "Port-mapped I/O GPIO drivers"
>  
>  config GPIO_I8255
>  	tristate
> +	select GPIO_REGMAP
>  	help
>  	  Enables support for the i8255 interface library functions. The i8255
>  	  interface library provides functions to facilitate communication with
> diff --git a/drivers/gpio/gpio-i8255.c b/drivers/gpio/gpio-i8255.c
> index 9b97db418df1..9ecb2e9b97f9 100644
> --- a/drivers/gpio/gpio-i8255.c
> +++ b/drivers/gpio/gpio-i8255.c
> @@ -4,23 +4,31 @@
>   * Copyright (C) 2022 William Breathitt Gray
>   */
>  #include <linux/bitmap.h>
> +#include <linux/device.h>
>  #include <linux/err.h>
>  #include <linux/export.h>
> +#include <linux/gpio/regmap.h>
>  #include <linux/io.h>
>  #include <linux/module.h>
> +#include <linux/regmap.h>
>  #include <linux/spinlock.h>
>  #include <linux/types.h>
>  
>  #include "gpio-i8255.h"
>  
> +#define I8255_NGPIO 24
> +#define I8255_NGPIO_PER_REG 8
>  #define I8255_CONTROL_PORTC_LOWER_DIRECTION BIT(0)
>  #define I8255_CONTROL_PORTB_DIRECTION BIT(1)
>  #define I8255_CONTROL_PORTC_UPPER_DIRECTION BIT(3)
>  #define I8255_CONTROL_PORTA_DIRECTION BIT(4)
>  #define I8255_CONTROL_MODE_SET BIT(7)
> -#define I8255_PORTA 0
> -#define I8255_PORTB 1
> -#define I8255_PORTC 2
> +#define I8255_PORTA 0x0
> +#define I8255_PORTB 0x1
> +#define I8255_PORTC 0x2
> +#define I8255_CONTROL 0x3
> +#define I8255_REG_DAT_BASE I8255_PORTA
> +#define I8255_REG_DIR_IN_BASE I8255_CONTROL
>  
>  static int i8255_get_port(struct i8255 __iomem *const ppi,
>  			  const unsigned long io_port, const unsigned long mask)
> @@ -31,20 +39,19 @@ static int i8255_get_port(struct i8255 __iomem *const ppi,
>  	return ioread8(&ppi[bank].port[ppi_port]) & mask;
>  }
>  
> -static u8 i8255_direction_mask(const unsigned long offset)
> +static int i8255_direction_mask(const unsigned int offset)
>  {
> -	const unsigned long port_offset = offset % 8;
> -	const unsigned long io_port = offset / 8;
> -	const unsigned long ppi_port = io_port % 3;
> +	const unsigned int stride = offset / I8255_NGPIO_PER_REG;
> +	const unsigned int line = offset % I8255_NGPIO_PER_REG;
>  
> -	switch (ppi_port) {
> +	switch (stride) {
>  	case I8255_PORTA:
>  		return I8255_CONTROL_PORTA_DIRECTION;
>  	case I8255_PORTB:
>  		return I8255_CONTROL_PORTB_DIRECTION;
>  	case I8255_PORTC:
>  		/* Port C can be configured by nibble */
> -		if (port_offset >= 4)
> +		if (line >= 4)
>  			return I8255_CONTROL_PORTC_UPPER_DIRECTION;
>  		return I8255_CONTROL_PORTC_LOWER_DIRECTION;
>  	default:
> @@ -53,6 +60,49 @@ static u8 i8255_direction_mask(const unsigned long offset)
>  	}
>  }
>  
> +static int i8255_ppi_init(struct regmap *const map, const unsigned int base)
> +{
> +	int err;
> +
> +	/* Configure all ports to MODE 0 output mode */
> +	err = regmap_write(map, base + I8255_CONTROL, I8255_CONTROL_MODE_SET);
> +	if (err)
> +		return err;
> +
> +	/* Initialize all GPIO to output 0 */
> +	err = regmap_write(map, base + I8255_PORTA, 0x00);
> +	if (err)
> +		return err;
> +	err = regmap_write(map, base + I8255_PORTB, 0x00);
> +	if (err)
> +		return err;
> +	return regmap_write(map, base + I8255_PORTC, 0x00);
> +}
> +
> +static int i8255_reg_mask_xlate(struct gpio_regmap *gpio, unsigned int base,
> +				unsigned int offset, unsigned int *reg,
> +				unsigned int *mask)
> +{
> +	const unsigned int ppi = offset / I8255_NGPIO;
> +	const unsigned int ppi_offset = offset % I8255_NGPIO;
> +	const unsigned int stride = ppi_offset / I8255_NGPIO_PER_REG;
> +	const unsigned int line = ppi_offset % I8255_NGPIO_PER_REG;
> +
> +	switch (base) {
> +	case I8255_REG_DAT_BASE:
> +		*reg = base + stride + ppi * 4;
> +		*mask = BIT(line);
> +		return 0;
> +	case I8255_REG_DIR_IN_BASE:
> +		*reg = base + ppi * 4;
> +		*mask = i8255_direction_mask(ppi_offset);
> +		return 0;
> +	default:
> +		/* Should never reach this path */
> +		return -EINVAL;
> +	}
> +}
> +
>  static void i8255_set_port(struct i8255 __iomem *const ppi,
>  			   struct i8255_state *const state,
>  			   const unsigned long io_port,
> @@ -93,7 +143,7 @@ void i8255_direction_input(struct i8255 __iomem *const ppi,
>  	spin_lock_irqsave(&state[bank].lock, flags);
>  
>  	state[bank].control_state |= I8255_CONTROL_MODE_SET;
> -	state[bank].control_state |= i8255_direction_mask(offset);
> +	state[bank].control_state |= i8255_direction_mask(offset % 24);
>  
>  	iowrite8(state[bank].control_state, &ppi[bank].control);
>  
> @@ -125,7 +175,7 @@ void i8255_direction_output(struct i8255 __iomem *const ppi,
>  	spin_lock_irqsave(&state[bank].lock, flags);
>  
>  	state[bank].control_state |= I8255_CONTROL_MODE_SET;
> -	state[bank].control_state &= ~i8255_direction_mask(offset);
> +	state[bank].control_state &= ~i8255_direction_mask(offset % 24);
>  
>  	iowrite8(state[bank].control_state, &ppi[bank].control);
>  
> @@ -165,7 +215,7 @@ int i8255_get_direction(const struct i8255_state *const state,
>  	const unsigned long io_port = offset / 8;
>  	const unsigned long bank = io_port / 3;
>  
> -	return !!(state[bank].control_state & i8255_direction_mask(offset));
> +	return !!(state[bank].control_state & i8255_direction_mask(offset % 24));
>  }
>  EXPORT_SYMBOL_NS_GPL(i8255_get_direction, I8255);
>  
> @@ -282,6 +332,51 @@ void i8255_state_init(struct i8255_state *const state,
>  }
>  EXPORT_SYMBOL_NS_GPL(i8255_state_init, I8255);
>  
> +/**
> + * devm_i8255_regmap_register - Register an i8255 GPIO controller
> + * @dev:	device that is registering this i8255 GPIO device
> + * @config:	configuration for i8255_regmap_config
> + *
> + * Registers an Intel 8255 Programmable Peripheral Interface GPIO controller.
> + * Returns 0 on success and negative error number on failure.
> + */
> +int devm_i8255_regmap_register(struct device *const dev,
> +			       const struct i8255_regmap_config *const config)
> +{
> +	struct gpio_regmap_config gpio_config = {0};
> +	unsigned long i;
> +	int err;
> +
> +	if (!config->parent)
> +		return -EINVAL;
> +
> +	if (!config->map)
> +		return -EINVAL;
> +
> +	if (!config->num_ppi)
> +		return -EINVAL;
> +
> +	for (i = 0; i < config->num_ppi; i++) {
> +		err = i8255_ppi_init(config->map, i * 4);
> +		if (err)
> +			return err;
> +	}
> +
> +	gpio_config.parent = config->parent;
> +	gpio_config.regmap = config->map;
> +	gpio_config.ngpio = I8255_NGPIO * config->num_ppi;
> +	gpio_config.names = config->names;
> +	gpio_config.reg_dat_base = GPIO_REGMAP_ADDR(I8255_REG_DAT_BASE);
> +	gpio_config.reg_set_base = GPIO_REGMAP_ADDR(I8255_REG_DAT_BASE);
> +	gpio_config.reg_dir_in_base = GPIO_REGMAP_ADDR(I8255_REG_DIR_IN_BASE);
> +	gpio_config.ngpio_per_reg = I8255_NGPIO_PER_REG;
> +	gpio_config.irq_domain = config->domain;
> +	gpio_config.reg_mask_xlate = i8255_reg_mask_xlate;
> +
> +	return PTR_ERR_OR_ZERO(devm_gpio_regmap_register(dev, &gpio_config));
> +}
> +EXPORT_SYMBOL_NS_GPL(devm_i8255_regmap_register, I8255);
> +
>  MODULE_AUTHOR("William Breathitt Gray");
>  MODULE_DESCRIPTION("Intel 8255 Programmable Peripheral Interface");
>  MODULE_LICENSE("GPL");
> diff --git a/drivers/gpio/gpio-i8255.h b/drivers/gpio/gpio-i8255.h
> index d9084aae9446..6ec987835c14 100644
> --- a/drivers/gpio/gpio-i8255.h
> +++ b/drivers/gpio/gpio-i8255.h
> @@ -3,6 +3,9 @@
>  #ifndef _I8255_H_
>  #define _I8255_H_

> +#include <linux/device.h>
> +#include <linux/irqdomain.h>
> +#include <linux/regmap.h>

As far as I can see you have no users for these headers. You may inform
compiler by providing forward declarations. Like

	struct device;


after the inclusion block.

>  #include <linux/spinlock.h>
>  #include <linux/types.h>
>  
> @@ -26,6 +29,30 @@ struct i8255_state {
>  	u8 control_state;
>  };
>  
> +#define i8255_volatile_regmap_range(_base) regmap_reg_range(_base, _base + 0x2)
> +
> +/**
> + * struct i8255_regmap_config - Configuration for the register map of an i8255
> + * @parent:	parent device
> + * @map:	regmap for the i8255
> + * @num_ppi:	number of i8255 Programmable Peripheral Interface
> + * @names:	(optional) array of names for gpios
> + * @domain:	(optional) IRQ domain if the controller is interrupt-capable

> + * Note: The regmap is expected to have cache enabled and i8255 control
> + * registers not marked as volatile.

Have you considered to catch wrong configurations by BUILD_BUG_ON() /
static_assert() / another means of validation?

> + */
> +struct i8255_regmap_config {
> +	struct device *parent;
> +	struct regmap *map;
> +	int num_ppi;
> +	const char *const *names;
> +	struct irq_domain *domain;
> +};
> +
> +int devm_i8255_regmap_register(struct device *dev,
> +			       const struct i8255_regmap_config *config);
> +
>  void i8255_direction_input(struct i8255 __iomem *ppi, struct i8255_state *state,
>  			   unsigned long offset);
>  void i8255_direction_output(struct i8255 __iomem *ppi,
> -- 
> 2.38.1
> 

-- 
With Best Regards,
Andy Shevchenko