xref: /linux/drivers/gpio/gpio-i8255.c (revision f9bff0e31881d03badf191d3b0005839391f5f2b)
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 
30 static 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 
51 static 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 
70 static 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  */
102 int 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 }
137 EXPORT_SYMBOL_NS_GPL(devm_i8255_regmap_register, I8255);
138 
139 MODULE_AUTHOR("William Breathitt Gray");
140 MODULE_DESCRIPTION("Intel 8255 Programmable Peripheral Interface");
141 MODULE_LICENSE("GPL");
142