simple_gpio.c revision 3d64de9c50619d32eb71d993d23a50b98d12d3c0 
1/*
2 * Simple Memory-Mapped GPIOs
3 *
4 * Copyright (c) MontaVista Software, Inc. 2008.
5 *
6 * Author: Anton Vorontsov <avorontsov@ru.mvista.com>
7 *
8 * This program is free software; you can redistribute  it and/or modify it
9 * under  the terms of  the GNU General  Public License as published by the
10 * Free Software Foundation;  either version 2 of the  License, or (at your
11 * option) any later version.
12 */
13
14#include <linux/init.h>
15#include <linux/kernel.h>
16#include <linux/module.h>
17#include <linux/spinlock.h>
18#include <linux/types.h>
19#include <linux/ioport.h>
20#include <linux/io.h>
21#include <linux/of.h>
22#include <linux/of_gpio.h>
23#include <linux/gpio.h>
24#include <asm/prom.h>
25#include "simple_gpio.h"
26
27struct u8_gpio_chip {
28	struct of_mm_gpio_chip mm_gc;
29	spinlock_t lock;
30
31	/* shadowed data register to clear/set bits safely */
32	u8 data;
33};
34
35static struct u8_gpio_chip *to_u8_gpio_chip(struct of_mm_gpio_chip *mm_gc)
36{
37	return container_of(mm_gc, struct u8_gpio_chip, mm_gc);
38}
39
40static u8 u8_pin2mask(unsigned int pin)
41{
42	return 1 << (8 - 1 - pin);
43}
44
45static int u8_gpio_get(struct gpio_chip *gc, unsigned int gpio)
46{
47	struct of_mm_gpio_chip *mm_gc = to_of_mm_gpio_chip(gc);
48
49	return in_8(mm_gc->regs) & u8_pin2mask(gpio);
50}
51
52static void u8_gpio_set(struct gpio_chip *gc, unsigned int gpio, int val)
53{
54	struct of_mm_gpio_chip *mm_gc = to_of_mm_gpio_chip(gc);
55	struct u8_gpio_chip *u8_gc = to_u8_gpio_chip(mm_gc);
56	unsigned long flags;
57
58	spin_lock_irqsave(&u8_gc->lock, flags);
59
60	if (val)
61		u8_gc->data |= u8_pin2mask(gpio);
62	else
63		u8_gc->data &= ~u8_pin2mask(gpio);
64
65	out_8(mm_gc->regs, u8_gc->data);
66
67	spin_unlock_irqrestore(&u8_gc->lock, flags);
68}
69
70static int u8_gpio_dir_in(struct gpio_chip *gc, unsigned int gpio)
71{
72	return 0;
73}
74
75static int u8_gpio_dir_out(struct gpio_chip *gc, unsigned int gpio, int val)
76{
77	u8_gpio_set(gc, gpio, val);
78	return 0;
79}
80
81static void u8_gpio_save_regs(struct of_mm_gpio_chip *mm_gc)
82{
83	struct u8_gpio_chip *u8_gc = to_u8_gpio_chip(mm_gc);
84
85	u8_gc->data = in_8(mm_gc->regs);
86}
87
88static int __init u8_simple_gpiochip_add(struct device_node *np)
89{
90	int ret;
91	struct u8_gpio_chip *u8_gc;
92	struct of_mm_gpio_chip *mm_gc;
93	struct of_gpio_chip *of_gc;
94	struct gpio_chip *gc;
95
96	u8_gc = kzalloc(sizeof(*u8_gc), GFP_KERNEL);
97	if (!u8_gc)
98		return -ENOMEM;
99
100	spin_lock_init(&u8_gc->lock);
101
102	mm_gc = &u8_gc->mm_gc;
103	of_gc = &mm_gc->of_gc;
104	gc = &of_gc->gc;
105
106	mm_gc->save_regs = u8_gpio_save_regs;
107	of_gc->gpio_cells = 2;
108	gc->ngpio = 8;
109	gc->direction_input = u8_gpio_dir_in;
110	gc->direction_output = u8_gpio_dir_out;
111	gc->get = u8_gpio_get;
112	gc->set = u8_gpio_set;
113
114	ret = of_mm_gpiochip_add(np, mm_gc);
115	if (ret)
116		goto err;
117	return 0;
118err:
119	kfree(u8_gc);
120	return ret;
121}
122
123void __init simple_gpiochip_init(const char *compatible)
124{
125	struct device_node *np;
126
127	for_each_compatible_node(np, NULL, compatible) {
128		int ret;
129		struct resource r;
130
131		ret = of_address_to_resource(np, 0, &r);
132		if (ret)
133			goto err;
134
135		switch (resource_size(&r)) {
136		case 1:
137			ret = u8_simple_gpiochip_add(np);
138			if (ret)
139				goto err;
140			break;
141		default:
142			/*
143			 * Whenever you need support for GPIO bank width > 1,
144			 * please just turn u8_ code into huge macros, and
145			 * construct needed uX_ code with it.
146			 */
147			ret = -ENOSYS;
148			goto err;
149		}
150		continue;
151err:
152		pr_err("%s: registration failed, status %d\n",
153		       np->full_name, ret);
154	}
155}
156