1/*
2 * Copyright (C) 2015 Texas Instruments Incorporated - http://www.ti.com/
3 *	Andrew F. Davis <afd@ti.com>
4 *
5 * This program is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU General Public License version 2 as
7 * published by the Free Software Foundation.
8 *
9 * This program is distributed "as is" WITHOUT ANY WARRANTY of any
10 * kind, whether expressed or implied; without even the implied warranty
11 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12 * GNU General Public License version 2 for more details.
13 */
14
15#include <linux/bitmap.h>
16#include <linux/bitops.h>
17#include <linux/delay.h>
18#include <linux/gpio/consumer.h>
19#include <linux/gpio/driver.h>
20#include <linux/module.h>
21#include <linux/mutex.h>
22#include <linux/spi/spi.h>
23
24#define DEFAULT_NGPIO 8
25
26/**
27 * struct pisosr_gpio - GPIO driver data
28 * @chip: GPIO controller chip
29 * @spi: SPI device pointer
30 * @buffer: Buffer for device reads
31 * @buffer_size: Size of buffer
32 * @load_gpio: GPIO pin used to load input into device
33 * @lock: Protects read sequences
34 */
35struct pisosr_gpio {
36	struct gpio_chip chip;
37	struct spi_device *spi;
38	u8 *buffer;
39	size_t buffer_size;
40	struct gpio_desc *load_gpio;
41	struct mutex lock;
42};
43
44static int pisosr_gpio_refresh(struct pisosr_gpio *gpio)
45{
46	int ret;
47
48	mutex_lock(&gpio->lock);
49
50	if (gpio->load_gpio) {
51		gpiod_set_value_cansleep(gpio->load_gpio, 1);
52		udelay(1); /* registers load time (~10ns) */
53		gpiod_set_value_cansleep(gpio->load_gpio, 0);
54		udelay(1); /* registers recovery time (~5ns) */
55	}
56
57	ret = spi_read(gpio->spi, gpio->buffer, gpio->buffer_size);
58
59	mutex_unlock(&gpio->lock);
60
61	return ret;
62}
63
64static int pisosr_gpio_get_direction(struct gpio_chip *chip,
65				     unsigned offset)
66{
67	/* This device always input */
68	return GPIO_LINE_DIRECTION_IN;
69}
70
71static int pisosr_gpio_direction_input(struct gpio_chip *chip,
72				       unsigned offset)
73{
74	/* This device always input */
75	return 0;
76}
77
78static int pisosr_gpio_direction_output(struct gpio_chip *chip,
79					unsigned offset, int value)
80{
81	/* This device is input only */
82	return -EINVAL;
83}
84
85static int pisosr_gpio_get(struct gpio_chip *chip, unsigned offset)
86{
87	struct pisosr_gpio *gpio = gpiochip_get_data(chip);
88
89	/* Refresh may not always be needed */
90	pisosr_gpio_refresh(gpio);
91
92	return (gpio->buffer[offset / 8] >> (offset % 8)) & 0x1;
93}
94
95static int pisosr_gpio_get_multiple(struct gpio_chip *chip,
96				    unsigned long *mask, unsigned long *bits)
97{
98	struct pisosr_gpio *gpio = gpiochip_get_data(chip);
99	unsigned long offset;
100	unsigned long gpio_mask;
101	unsigned long buffer_state;
102
103	pisosr_gpio_refresh(gpio);
104
105	bitmap_zero(bits, chip->ngpio);
106	for_each_set_clump8(offset, gpio_mask, mask, chip->ngpio) {
107		buffer_state = gpio->buffer[offset / 8] & gpio_mask;
108		bitmap_set_value8(bits, buffer_state, offset);
109	}
110
111	return 0;
112}
113
114static const struct gpio_chip template_chip = {
115	.label			= "pisosr-gpio",
116	.owner			= THIS_MODULE,
117	.get_direction		= pisosr_gpio_get_direction,
118	.direction_input	= pisosr_gpio_direction_input,
119	.direction_output	= pisosr_gpio_direction_output,
120	.get			= pisosr_gpio_get,
121	.get_multiple		= pisosr_gpio_get_multiple,
122	.base			= -1,
123	.ngpio			= DEFAULT_NGPIO,
124	.can_sleep		= true,
125};
126
127static int pisosr_gpio_probe(struct spi_device *spi)
128{
129	struct device *dev = &spi->dev;
130	struct pisosr_gpio *gpio;
131	int ret;
132
133	gpio = devm_kzalloc(dev, sizeof(*gpio), GFP_KERNEL);
134	if (!gpio)
135		return -ENOMEM;
136
137	spi_set_drvdata(spi, gpio);
138
139	gpio->chip = template_chip;
140	gpio->chip.parent = dev;
141	of_property_read_u16(dev->of_node, "ngpios", &gpio->chip.ngpio);
142
143	gpio->spi = spi;
144
145	gpio->buffer_size = DIV_ROUND_UP(gpio->chip.ngpio, 8);
146	gpio->buffer = devm_kzalloc(dev, gpio->buffer_size, GFP_KERNEL);
147	if (!gpio->buffer)
148		return -ENOMEM;
149
150	gpio->load_gpio = devm_gpiod_get_optional(dev, "load", GPIOD_OUT_LOW);
151	if (IS_ERR(gpio->load_gpio))
152		return dev_err_probe(dev, PTR_ERR(gpio->load_gpio),
153				     "Unable to allocate load GPIO\n");
154
155	mutex_init(&gpio->lock);
156
157	ret = gpiochip_add_data(&gpio->chip, gpio);
158	if (ret < 0) {
159		dev_err(dev, "Unable to register gpiochip\n");
160		return ret;
161	}
162
163	return 0;
164}
165
166static int pisosr_gpio_remove(struct spi_device *spi)
167{
168	struct pisosr_gpio *gpio = spi_get_drvdata(spi);
169
170	gpiochip_remove(&gpio->chip);
171
172	mutex_destroy(&gpio->lock);
173
174	return 0;
175}
176
177static const struct spi_device_id pisosr_gpio_id_table[] = {
178	{ "pisosr-gpio", },
179	{ /* sentinel */ }
180};
181MODULE_DEVICE_TABLE(spi, pisosr_gpio_id_table);
182
183static const struct of_device_id pisosr_gpio_of_match_table[] = {
184	{ .compatible = "pisosr-gpio", },
185	{ /* sentinel */ }
186};
187MODULE_DEVICE_TABLE(of, pisosr_gpio_of_match_table);
188
189static struct spi_driver pisosr_gpio_driver = {
190	.driver = {
191		.name = "pisosr-gpio",
192		.of_match_table = pisosr_gpio_of_match_table,
193	},
194	.probe = pisosr_gpio_probe,
195	.remove = pisosr_gpio_remove,
196	.id_table = pisosr_gpio_id_table,
197};
198module_spi_driver(pisosr_gpio_driver);
199
200MODULE_AUTHOR("Andrew F. Davis <afd@ti.com>");
201MODULE_DESCRIPTION("SPI Compatible PISO Shift Register GPIO Driver");
202MODULE_LICENSE("GPL v2");
203