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, reg: 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, reg: base + I8255_PORTA, val: 0x00);
62 if (err)
63 return err;
64 err = regmap_write(map, reg: base + I8255_PORTB, val: 0x00);
65 if (err)
66 return err;
67 return regmap_write(map, reg: base + I8255_PORTC, val: 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(offset: 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(map: config->map, base: 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(ptr: devm_gpio_regmap_register(dev, config: &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");
142

source code of linux/drivers/gpio/gpio-i8255.c