1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Intel 8255 Programmable Peripheral Interface
  4 * Copyright (C) 2022 William Breathitt Gray
  5 */
  6#include <linux/bits.h>
  7#include <linux/device.h>
  8#include <linux/err.h>
  9#include <linux/export.h>
 10#include <linux/gpio/regmap.h>
 11#include <linux/module.h>
 12#include <linux/regmap.h>
 13
 14#include "gpio-i8255.h"
 15
 16#define I8255_NGPIO 24
 17#define I8255_NGPIO_PER_REG 8
 18#define I8255_CONTROL_PORTC_LOWER_DIRECTION BIT(0)
 19#define I8255_CONTROL_PORTB_DIRECTION BIT(1)
 20#define I8255_CONTROL_PORTC_UPPER_DIRECTION BIT(3)
 21#define I8255_CONTROL_PORTA_DIRECTION BIT(4)
 22#define I8255_CONTROL_MODE_SET BIT(7)
 23#define I8255_PORTA 0x0
 24#define I8255_PORTB 0x1
 25#define I8255_PORTC 0x2
 26#define I8255_CONTROL 0x3
 27#define I8255_REG_DAT_BASE I8255_PORTA
 28#define I8255_REG_DIR_IN_BASE I8255_CONTROL
 29
 30static int i8255_direction_mask(const unsigned int offset)
 31{
 32	const unsigned int stride = offset / I8255_NGPIO_PER_REG;
 33	const unsigned int line = offset % I8255_NGPIO_PER_REG;
 34
 35	switch (stride) {
 36	case I8255_PORTA:
 37		return I8255_CONTROL_PORTA_DIRECTION;
 38	case I8255_PORTB:
 39		return I8255_CONTROL_PORTB_DIRECTION;
 40	case I8255_PORTC:
 41		/* Port C can be configured by nibble */
 42		if (line >= 4)
 43			return I8255_CONTROL_PORTC_UPPER_DIRECTION;
 44		return I8255_CONTROL_PORTC_LOWER_DIRECTION;
 45	default:
 46		/* Should never reach this path */
 47		return 0;
 48	}
 49}
 50
 51static int i8255_ppi_init(struct regmap *const map, const unsigned int base)
 52{
 53	int err;
 54
 55	/* Configure all ports to MODE 0 output mode */
 56	err = regmap_write(map, base + I8255_CONTROL, I8255_CONTROL_MODE_SET);
 57	if (err)
 58		return err;
 59
 60	/* Initialize all GPIO to output 0 */
 61	err = regmap_write(map, base + I8255_PORTA, 0x00);
 62	if (err)
 63		return err;
 64	err = regmap_write(map, base + I8255_PORTB, 0x00);
 65	if (err)
 66		return err;
 67	return regmap_write(map, base + I8255_PORTC, 0x00);
 68}
 69
 70static int i8255_reg_mask_xlate(struct gpio_regmap *gpio, unsigned int base,
 71				unsigned int offset, unsigned int *reg,
 72				unsigned int *mask)
 73{
 74	const unsigned int ppi = offset / I8255_NGPIO;
 75	const unsigned int ppi_offset = offset % I8255_NGPIO;
 76	const unsigned int stride = ppi_offset / I8255_NGPIO_PER_REG;
 77	const unsigned int line = ppi_offset % I8255_NGPIO_PER_REG;
 78
 79	switch (base) {
 80	case I8255_REG_DAT_BASE:
 81		*reg = base + stride + ppi * 4;
 82		*mask = BIT(line);
 83		return 0;
 84	case I8255_REG_DIR_IN_BASE:
 85		*reg = base + ppi * 4;
 86		*mask = i8255_direction_mask(ppi_offset);
 87		return 0;
 88	default:
 89		/* Should never reach this path */
 90		return -EINVAL;
 91	}
 92}
 93
 94/**
 95 * devm_i8255_regmap_register - Register an i8255 GPIO controller
 96 * @dev:	device that is registering this i8255 GPIO device
 97 * @config:	configuration for i8255_regmap_config
 98 *
 99 * Registers an Intel 8255 Programmable Peripheral Interface GPIO controller.
100 * Returns 0 on success and negative error number on failure.
101 */
102int devm_i8255_regmap_register(struct device *const dev,
103			       const struct i8255_regmap_config *const config)
104{
105	struct gpio_regmap_config gpio_config = {0};
106	unsigned long i;
107	int err;
108
109	if (!config->parent)
110		return -EINVAL;
111
112	if (!config->map)
113		return -EINVAL;
114
115	if (!config->num_ppi)
116		return -EINVAL;
117
118	for (i = 0; i < config->num_ppi; i++) {
119		err = i8255_ppi_init(config->map, i * 4);
120		if (err)
121			return err;
122	}
123
124	gpio_config.parent = config->parent;
125	gpio_config.regmap = config->map;
126	gpio_config.ngpio = I8255_NGPIO * config->num_ppi;
127	gpio_config.names = config->names;
128	gpio_config.reg_dat_base = GPIO_REGMAP_ADDR(I8255_REG_DAT_BASE);
129	gpio_config.reg_set_base = GPIO_REGMAP_ADDR(I8255_REG_DAT_BASE);
130	gpio_config.reg_dir_in_base = GPIO_REGMAP_ADDR(I8255_REG_DIR_IN_BASE);
131	gpio_config.ngpio_per_reg = I8255_NGPIO_PER_REG;
132	gpio_config.irq_domain = config->domain;
133	gpio_config.reg_mask_xlate = i8255_reg_mask_xlate;
134
135	return PTR_ERR_OR_ZERO(devm_gpio_regmap_register(dev, &gpio_config));
136}
137EXPORT_SYMBOL_NS_GPL(devm_i8255_regmap_register, I8255);
138
139MODULE_AUTHOR("William Breathitt Gray");
140MODULE_DESCRIPTION("Intel 8255 Programmable Peripheral Interface");
141MODULE_LICENSE("GPL");