/*
 * Janz MODULbus VMOD-TTL GPIO Driver
 *
 * Copyright (c) 2010 Ira W. Snyder <iws@ovro.caltech.edu>
 *
 * 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/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/io.h>
#include <linux/gpio.h>
#include <linux/slab.h>

#include <linux/mfd/janz.h>

#define DRV_NAME "janz-ttl"

#define PORTA_DIRECTION         0x23
#define PORTB_DIRECTION         0x2B
#define PORTC_DIRECTION         0x06
#define PORTA_IOCTL             0x24
#define PORTB_IOCTL             0x2C
#define PORTC_IOCTL             0x07

#define MASTER_INT_CTL          0x00
#define MASTER_CONF_CTL         0x01

#define CONF_PAE                (1 << 2)
#define CONF_PBE                (1 << 7)
#define CONF_PCE                (1 << 4)

struct ttl_control_regs {
        __be16 portc;
        __be16 portb;
        __be16 porta;
        __be16 control;
};

struct ttl_module {
        struct gpio_chip gpio;

        /* base address of registers */
        struct ttl_control_regs __iomem *regs;

        u8 portc_shadow;
        u8 portb_shadow;
        u8 porta_shadow;

        spinlock_t lock;
};

static int ttl_get_value(struct gpio_chip *gpio, unsigned offset)
{
        struct ttl_module *mod = dev_get_drvdata(gpio->parent);
        u8 *shadow;
        int ret;

        if (offset < 8) {
                shadow = &mod->porta_shadow;
        } else if (offset < 16) {
                shadow = &mod->portb_shadow;
                offset -= 8;
        } else {
                shadow = &mod->portc_shadow;
                offset -= 16;
        }

        spin_lock(&mod->lock);
        ret = *shadow & (1 << offset);
        spin_unlock(&mod->lock);
        return !!ret;
}

static void ttl_set_value(struct gpio_chip *gpio, unsigned offset, int value)
{
        struct ttl_module *mod = dev_get_drvdata(gpio->parent);
        void __iomem *port;
        u8 *shadow;

        if (offset < 8) {
                port = &mod->regs->porta;
                shadow = &mod->porta_shadow;
        } else if (offset < 16) {
                port = &mod->regs->portb;
                shadow = &mod->portb_shadow;
                offset -= 8;
        } else {
                port = &mod->regs->portc;
                shadow = &mod->portc_shadow;
                offset -= 16;
        }

        spin_lock(&mod->lock);
        if (value)
                *shadow |= (1 << offset);
        else
                *shadow &= ~(1 << offset);

        iowrite16be(*shadow, port);
        spin_unlock(&mod->lock);
}

static void ttl_write_reg(struct ttl_module *mod, u8 reg, u16 val)
{
        iowrite16be(reg, &mod->regs->control);
        iowrite16be(val, &mod->regs->control);
}

static void ttl_setup_device(struct ttl_module *mod)
{
        /* reset the device to a known state */
        iowrite16be(0x0000, &mod->regs->control);
        iowrite16be(0x0001, &mod->regs->control);
        iowrite16be(0x0000, &mod->regs->control);

        /* put all ports in open-drain mode */
        ttl_write_reg(mod, PORTA_IOCTL, 0x00ff);
        ttl_write_reg(mod, PORTB_IOCTL, 0x00ff);
        ttl_write_reg(mod, PORTC_IOCTL, 0x000f);

        /* set all ports as outputs */
        ttl_write_reg(mod, PORTA_DIRECTION, 0x0000);
        ttl_write_reg(mod, PORTB_DIRECTION, 0x0000);
        ttl_write_reg(mod, PORTC_DIRECTION, 0x0000);

        /* set all ports to drive zeroes */
        iowrite16be(0x0000, &mod->regs->porta);
        iowrite16be(0x0000, &mod->regs->portb);
        iowrite16be(0x0000, &mod->regs->portc);

        /* enable all ports */
        ttl_write_reg(mod, MASTER_CONF_CTL, CONF_PAE | CONF_PBE | CONF_PCE);
}

static int ttl_probe(struct platform_device *pdev)
{
        struct janz_platform_data *pdata;
        struct device *dev = &pdev->dev;
        struct ttl_module *mod;
        struct gpio_chip *gpio;
        struct resource *res;
        int ret;

        pdata = dev_get_platdata(&pdev->dev);
        if (!pdata) {
                dev_err(dev, "no platform data\n");
                return -ENXIO;
        }

        mod = devm_kzalloc(dev, sizeof(*mod), GFP_KERNEL);
        if (!mod)
                return -ENOMEM;

        platform_set_drvdata(pdev, mod);
        spin_lock_init(&mod->lock);

        /* get access to the MODULbus registers for this module */
        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        mod->regs = devm_ioremap_resource(dev, res);
        if (IS_ERR(mod->regs))
                return PTR_ERR(mod->regs);

        ttl_setup_device(mod);

        /* Initialize the GPIO data structures */
        gpio = &mod->gpio;
        gpio->parent = &pdev->dev;
        gpio->label = pdev->name;
        gpio->get = ttl_get_value;
        gpio->set = ttl_set_value;
        gpio->owner = THIS_MODULE;

        /* request dynamic allocation */
        gpio->base = -1;
        gpio->ngpio = 20;

        ret = devm_gpiochip_add_data(dev, gpio, NULL);
        if (ret) {
                dev_err(dev, "unable to add GPIO chip\n");
                return ret;
        }

        return 0;
}

static struct platform_driver ttl_driver = {
        .driver         = {
                .name   = DRV_NAME,
        },
        .probe          = ttl_probe,
};

module_platform_driver(ttl_driver);

MODULE_AUTHOR("Ira W. Snyder <iws@ovro.caltech.edu>");
MODULE_DESCRIPTION("Janz MODULbus VMOD-TTL Driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:janz-ttl");