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  */
35 struct 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 
pisosr_gpio_refresh(struct pisosr_gpio * gpio)44 static 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 
pisosr_gpio_get_direction(struct gpio_chip * chip,unsigned offset)64 static 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 
pisosr_gpio_direction_input(struct gpio_chip * chip,unsigned offset)71 static int pisosr_gpio_direction_input(struct gpio_chip *chip,
72 				       unsigned offset)
73 {
74 	/* This device always input */
75 	return 0;
76 }
77 
pisosr_gpio_direction_output(struct gpio_chip * chip,unsigned offset,int value)78 static 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 
pisosr_gpio_get(struct gpio_chip * chip,unsigned offset)85 static 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 
pisosr_gpio_get_multiple(struct gpio_chip * chip,unsigned long * mask,unsigned long * bits)95 static 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 
114 static 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 
pisosr_gpio_probe(struct spi_device * spi)127 static 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 
pisosr_gpio_remove(struct spi_device * spi)166 static 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 
177 static const struct spi_device_id pisosr_gpio_id_table[] = {
178 	{ "pisosr-gpio", },
179 	{ /* sentinel */ }
180 };
181 MODULE_DEVICE_TABLE(spi, pisosr_gpio_id_table);
182 
183 static const struct of_device_id pisosr_gpio_of_match_table[] = {
184 	{ .compatible = "pisosr-gpio", },
185 	{ /* sentinel */ }
186 };
187 MODULE_DEVICE_TABLE(of, pisosr_gpio_of_match_table);
188 
189 static 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 };
198 module_spi_driver(pisosr_gpio_driver);
199 
200 MODULE_AUTHOR("Andrew F. Davis <afd@ti.com>");
201 MODULE_DESCRIPTION("SPI Compatible PISO Shift Register GPIO Driver");
202 MODULE_LICENSE("GPL v2");
203