simple_gpio.c

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/*
 * Simple Memory-Mapped GPIOs
 *
 * Copyright (c) MontaVista Software, Inc. 2008.
 *
 * Author: Anton Vorontsov <[email protected]>
 *
 * This program is free software; you can redistribute  it and/or modify it
 * under  the terms of  the GNU General  Public License as published by the
 * Free Software Foundation;  either version 2 of the  License, or (at your
 * option) any later version.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/spinlock.h>
#include <linux/types.h>
#include <linux/ioport.h>
#include <linux/io.h>
#include <linux/of.h>
#include <linux/of_gpio.h>
#include <linux/gpio.h>
#include <linux/slab.h>
#include <asm/prom.h>
#include "simple_gpio.h"

struct u8_gpio_chip {
    struct of_mm_gpio_chip mm_gc;
    spinlock_t lock;

    /* shadowed data register to clear/set bits safely */
    u8 data;
};

static struct u8_gpio_chip *to_u8_gpio_chip(struct of_mm_gpio_chip *mm_gc)
{
    return container_of(mm_gc, struct u8_gpio_chip, mm_gc);
}

static u8 u8_pin2mask(unsigned int pin)
{
    return 1 << (8 - 1 - pin);
}

static int u8_gpio_get(struct gpio_chip *gc, unsigned int gpio)
{
    struct of_mm_gpio_chip *mm_gc = to_of_mm_gpio_chip(gc);

    return in_8(mm_gc->regs) & u8_pin2mask(gpio);
}

static void u8_gpio_set(struct gpio_chip *gc, unsigned int gpio, int val)
{
    struct of_mm_gpio_chip *mm_gc = to_of_mm_gpio_chip(gc);
    struct u8_gpio_chip *u8_gc = to_u8_gpio_chip(mm_gc);
    unsigned long flags;

    spin_lock_irqsave(&u8_gc->lock, flags);

    if (val)
        u8_gc->data |= u8_pin2mask(gpio);
    else
        u8_gc->data &= ~u8_pin2mask(gpio);

    out_8(mm_gc->regs, u8_gc->data);

    spin_unlock_irqrestore(&u8_gc->lock, flags);
}

static int u8_gpio_dir_in(struct gpio_chip *gc, unsigned int gpio)
{
    return 0;
}

static int u8_gpio_dir_out(struct gpio_chip *gc, unsigned int gpio, int val)
{
    u8_gpio_set(gc, gpio, val);
    return 0;
}

static void u8_gpio_save_regs(struct of_mm_gpio_chip *mm_gc)
{
    struct u8_gpio_chip *u8_gc = to_u8_gpio_chip(mm_gc);

    u8_gc->data = in_8(mm_gc->regs);
}

static int __init u8_simple_gpiochip_add(struct device_node *np)
{
    int ret;
    struct u8_gpio_chip *u8_gc;
    struct of_mm_gpio_chip *mm_gc;
    struct gpio_chip *gc;

    u8_gc = kzalloc(sizeof(*u8_gc), GFP_KERNEL);
    if (!u8_gc)
        return -ENOMEM;

    spin_lock_init(&u8_gc->lock);

    mm_gc = &u8_gc->mm_gc;
    gc = &mm_gc->gc;

    mm_gc->save_regs = u8_gpio_save_regs;
    gc->ngpio = 8;
    gc->direction_input = u8_gpio_dir_in;
    gc->direction_output = u8_gpio_dir_out;
    gc->get = u8_gpio_get;
    gc->set = u8_gpio_set;

    ret = of_mm_gpiochip_add(np, mm_gc);
    if (ret)
        goto err;
    return 0;
err:
    kfree(u8_gc);
    return ret;
}

void __init simple_gpiochip_init(const char *compatible)
{
    struct device_node *np;

    for_each_compatible_node(np, NULL, compatible) {
        int ret;
        struct resource r;

        ret = of_address_to_resource(np, 0, &r);
        if (ret)
            goto err;

        switch (resource_size(&r)) {
        case 1:
            ret = u8_simple_gpiochip_add(np);
            if (ret)
                goto err;
            break;
        default:
            /*
             * Whenever you need support for GPIO bank width > 1,
             * please just turn u8_ code into huge macros, and
             * construct needed uX_ code with it.
             */
            ret = -ENOSYS;
            goto err;
        }
        continue;
err:
        pr_err("%s: registration failed, status %d\n",
               np->full_name, ret);
    }
}