gpio-mm-lantiq.c

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/*
 *  This program is free software; you can redistribute it and/or modify it
 *  under the terms of the GNU General Public License version 2 as published
 *  by the Free Software Foundation.
 *
 *  Copyright (C) 2012 John Crispin <[email protected]>
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/platform_device.h>
#include <linux/mutex.h>
#include <linux/gpio.h>
#include <linux/of.h>
#include <linux/of_gpio.h>
#include <linux/io.h>
#include <linux/slab.h>

#include <lantiq_soc.h>

/*
 * By attaching hardware latches to the EBU it is possible to create output
 * only gpios. This driver configures a special memory address, which when
 * written to outputs 16 bit to the latches.
 */

#define LTQ_EBU_BUSCON  0x1e7ff     /* 16 bit access, slowest timing */
#define LTQ_EBU_WP  0x80000000  /* write protect bit */

struct ltq_mm {
    struct of_mm_gpio_chip mmchip;
    u16 shadow; /* shadow the latches state */
};

static void ltq_mm_apply(struct ltq_mm *chip)
{
    unsigned long flags;

    spin_lock_irqsave(&ebu_lock, flags);
    ltq_ebu_w32(LTQ_EBU_BUSCON, LTQ_EBU_BUSCON1);
    __raw_writew(chip->shadow, chip->mmchip.regs);
    ltq_ebu_w32(LTQ_EBU_BUSCON | LTQ_EBU_WP, LTQ_EBU_BUSCON1);
    spin_unlock_irqrestore(&ebu_lock, flags);
}

static void ltq_mm_set(struct gpio_chip *gc, unsigned offset, int value)
{
    struct of_mm_gpio_chip *mm_gc = to_of_mm_gpio_chip(gc);
    struct ltq_mm *chip =
        container_of(mm_gc, struct ltq_mm, mmchip);

    if (value)
        chip->shadow |= (1 << offset);
    else
        chip->shadow &= ~(1 << offset);
    ltq_mm_apply(chip);
}

static int ltq_mm_dir_out(struct gpio_chip *gc, unsigned offset, int value)
{
    ltq_mm_set(gc, offset, value);

    return 0;
}

static void ltq_mm_save_regs(struct of_mm_gpio_chip *mm_gc)
{
    struct ltq_mm *chip =
        container_of(mm_gc, struct ltq_mm, mmchip);

    /* tell the ebu controller which memory address we will be using */
    ltq_ebu_w32(CPHYSADDR(chip->mmchip.regs) | 0x1, LTQ_EBU_ADDRSEL1);

    ltq_mm_apply(chip);
}

static int ltq_mm_probe(struct platform_device *pdev)
{
    struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    struct ltq_mm *chip;
    const __be32 *shadow;
    int ret = 0;

    if (!res) {
        dev_err(&pdev->dev, "failed to get memory resource\n");
        return -ENOENT;
    }

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

    chip->mmchip.gc.ngpio = 16;
    chip->mmchip.gc.label = "gpio-mm-ltq";
    chip->mmchip.gc.direction_output = ltq_mm_dir_out;
    chip->mmchip.gc.set = ltq_mm_set;
    chip->mmchip.save_regs = ltq_mm_save_regs;

    /* store the shadow value if one was passed by the devicetree */
    shadow = of_get_property(pdev->dev.of_node, "lantiq,shadow", NULL);
    if (shadow)
        chip->shadow = be32_to_cpu(*shadow);

    ret = of_mm_gpiochip_add(pdev->dev.of_node, &chip->mmchip);
    if (ret)
        kfree(chip);
    return ret;
}

static const struct of_device_id ltq_mm_match[] = {
    { .compatible = "lantiq,gpio-mm" },
    {},
};
MODULE_DEVICE_TABLE(of, ltq_mm_match);

static struct platform_driver ltq_mm_driver = {
    .probe = ltq_mm_probe,
    .driver = {
        .name = "gpio-mm-ltq",
        .owner = THIS_MODULE,
        .of_match_table = ltq_mm_match,
    },
};

static int __init ltq_mm_init(void)
{
    return platform_driver_register(&ltq_mm_driver);
}

subsys_initcall(ltq_mm_init);