/*
 *  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 <john@phrozen.org>
 *
 */

#include <linux/slab.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/of_platform.h>
#include <linux/mutex.h>
#include <linux/gpio.h>
#include <linux/io.h>
#include <linux/of_gpio.h>
#include <linux/clk.h>
#include <linux/err.h>

#include <lantiq_soc.h>

/*
 * The Serial To Parallel (STP) is found on MIPS based Lantiq socs. It is a
 * peripheral controller used to drive external shift register cascades. At most
 * 3 groups of 8 bits can be driven. The hardware is able to allow the DSL modem
 * to drive the 2 LSBs of the cascade automatically.
 */

/* control register 0 */
#define XWAY_STP_CON0           0x00
/* control register 1 */
#define XWAY_STP_CON1           0x04
/* data register 0 */
#define XWAY_STP_CPU0           0x08
/* data register 1 */
#define XWAY_STP_CPU1           0x0C
/* access register */
#define XWAY_STP_AR             0x10

/* software or hardware update select bit */
#define XWAY_STP_CON_SWU        BIT(31)

/* automatic update rates */
#define XWAY_STP_2HZ            0
#define XWAY_STP_4HZ            BIT(23)
#define XWAY_STP_8HZ            BIT(24)
#define XWAY_STP_10HZ           (BIT(24) | BIT(23))
#define XWAY_STP_SPEED_MASK     (0xf << 23)

/* clock source for automatic update */
#define XWAY_STP_UPD_FPI        BIT(31)
#define XWAY_STP_UPD_MASK       (BIT(31) | BIT(30))

/* let the adsl core drive the 2 LSBs */
#define XWAY_STP_ADSL_SHIFT     24
#define XWAY_STP_ADSL_MASK      0x3

/* 2 groups of 3 bits can be driven by the phys */
#define XWAY_STP_PHY_MASK       0x7
#define XWAY_STP_PHY1_SHIFT     27
#define XWAY_STP_PHY2_SHIFT     15

/* STP has 3 groups of 8 bits */
#define XWAY_STP_GROUP0         BIT(0)
#define XWAY_STP_GROUP1         BIT(1)
#define XWAY_STP_GROUP2         BIT(2)
#define XWAY_STP_GROUP_MASK     (0x7)

/* Edge configuration bits */
#define XWAY_STP_FALLING        BIT(26)
#define XWAY_STP_EDGE_MASK      BIT(26)

#define xway_stp_r32(m, reg)            __raw_readl(m + reg)
#define xway_stp_w32(m, val, reg)       __raw_writel(val, m + reg)
#define xway_stp_w32_mask(m, clear, set, reg) \
                ltq_w32((ltq_r32(m + reg) & ~(clear)) | (set), \
                m + reg)

struct xway_stp {
        struct gpio_chip gc;
        void __iomem *virt;
        u32 edge;       /* rising or falling edge triggered shift register */
        u32 shadow;     /* shadow the shift registers state */
        u8 groups;      /* we can drive 1-3 groups of 8bit each */
        u8 dsl;         /* the 2 LSBs can be driven by the dsl core */
        u8 phy1;        /* 3 bits can be driven by phy1 */
        u8 phy2;        /* 3 bits can be driven by phy2 */
        u8 reserved;    /* mask out the hw driven bits in gpio_request */
};

/**
 * xway_stp_set() - gpio_chip->set - set gpios.
 * @gc:     Pointer to gpio_chip device structure.
 * @gpio:   GPIO signal number.
 * @val:    Value to be written to specified signal.
 *
 * Set the shadow value and call ltq_ebu_apply.
 */
static void xway_stp_set(struct gpio_chip *gc, unsigned gpio, int val)
{
        struct xway_stp *chip = gpiochip_get_data(gc);

        if (val)
                chip->shadow |= BIT(gpio);
        else
                chip->shadow &= ~BIT(gpio);
        xway_stp_w32(chip->virt, chip->shadow, XWAY_STP_CPU0);
        xway_stp_w32_mask(chip->virt, 0, XWAY_STP_CON_SWU, XWAY_STP_CON0);
}

/**
 * xway_stp_dir_out() - gpio_chip->dir_out - set gpio direction.
 * @gc:     Pointer to gpio_chip device structure.
 * @gpio:   GPIO signal number.
 * @val:    Value to be written to specified signal.
 *
 * Same as xway_stp_set, always returns 0.
 */
static int xway_stp_dir_out(struct gpio_chip *gc, unsigned gpio, int val)
{
        xway_stp_set(gc, gpio, val);

        return 0;
}

/**
 * xway_stp_request() - gpio_chip->request
 * @gc:     Pointer to gpio_chip device structure.
 * @gpio:   GPIO signal number.
 *
 * We mask out the HW driven pins
 */
static int xway_stp_request(struct gpio_chip *gc, unsigned gpio)
{
        struct xway_stp *chip = gpiochip_get_data(gc);

        if ((gpio < 8) && (chip->reserved & BIT(gpio))) {
                dev_err(gc->parent, "GPIO %d is driven by hardware\n", gpio);
                return -ENODEV;
        }

        return 0;
}

/**
 * xway_stp_hw_init() - Configure the STP unit and enable the clock gate
 * @virt: pointer to the remapped register range
 */
static int xway_stp_hw_init(struct xway_stp *chip)
{
        /* sane defaults */
        xway_stp_w32(chip->virt, 0, XWAY_STP_AR);
        xway_stp_w32(chip->virt, 0, XWAY_STP_CPU0);
        xway_stp_w32(chip->virt, 0, XWAY_STP_CPU1);
        xway_stp_w32(chip->virt, XWAY_STP_CON_SWU, XWAY_STP_CON0);
        xway_stp_w32(chip->virt, 0, XWAY_STP_CON1);

        /* apply edge trigger settings for the shift register */
        xway_stp_w32_mask(chip->virt, XWAY_STP_EDGE_MASK,
                                chip->edge, XWAY_STP_CON0);

        /* apply led group settings */
        xway_stp_w32_mask(chip->virt, XWAY_STP_GROUP_MASK,
                                chip->groups, XWAY_STP_CON1);

        /* tell the hardware which pins are controlled by the dsl modem */
        xway_stp_w32_mask(chip->virt,
                        XWAY_STP_ADSL_MASK << XWAY_STP_ADSL_SHIFT,
                        chip->dsl << XWAY_STP_ADSL_SHIFT,
                        XWAY_STP_CON0);

        /* tell the hardware which pins are controlled by the phys */
        xway_stp_w32_mask(chip->virt,
                        XWAY_STP_PHY_MASK << XWAY_STP_PHY1_SHIFT,
                        chip->phy1 << XWAY_STP_PHY1_SHIFT,
                        XWAY_STP_CON0);
        xway_stp_w32_mask(chip->virt,
                        XWAY_STP_PHY_MASK << XWAY_STP_PHY2_SHIFT,
                        chip->phy2 << XWAY_STP_PHY2_SHIFT,
                        XWAY_STP_CON1);

        /* mask out the hw driven bits in gpio_request */
        chip->reserved = (chip->phy2 << 5) | (chip->phy1 << 2) | chip->dsl;

        /*
         * if we have pins that are driven by hw, we need to tell the stp what
         * clock to use as a timer.
         */
        if (chip->reserved)
                xway_stp_w32_mask(chip->virt, XWAY_STP_UPD_MASK,
                        XWAY_STP_UPD_FPI, XWAY_STP_CON1);

        return 0;
}

static int xway_stp_probe(struct platform_device *pdev)
{
        struct resource *res;
        u32 shadow, groups, dsl, phy;
        struct xway_stp *chip;
        struct clk *clk;
        int ret = 0;

        chip = devm_kzalloc(&pdev->dev, sizeof(*chip), GFP_KERNEL);
        if (!chip)
                return -ENOMEM;

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        chip->virt = devm_ioremap_resource(&pdev->dev, res);
        if (IS_ERR(chip->virt))
                return PTR_ERR(chip->virt);

        chip->gc.parent = &pdev->dev;
        chip->gc.label = "stp-xway";
        chip->gc.direction_output = xway_stp_dir_out;
        chip->gc.set = xway_stp_set;
        chip->gc.request = xway_stp_request;
        chip->gc.base = -1;
        chip->gc.owner = THIS_MODULE;

        /* store the shadow value if one was passed by the devicetree */
        if (!of_property_read_u32(pdev->dev.of_node, "lantiq,shadow", &shadow))
                chip->shadow = shadow;

        /* find out which gpio groups should be enabled */
        if (!of_property_read_u32(pdev->dev.of_node, "lantiq,groups", &groups))
                chip->groups = groups & XWAY_STP_GROUP_MASK;
        else
                chip->groups = XWAY_STP_GROUP0;
        chip->gc.ngpio = fls(chip->groups) * 8;

        /* find out which gpios are controlled by the dsl core */
        if (!of_property_read_u32(pdev->dev.of_node, "lantiq,dsl", &dsl))
                chip->dsl = dsl & XWAY_STP_ADSL_MASK;

        /* find out which gpios are controlled by the phys */
        if (of_machine_is_compatible("lantiq,ar9") ||
                        of_machine_is_compatible("lantiq,gr9") ||
                        of_machine_is_compatible("lantiq,vr9")) {
                if (!of_property_read_u32(pdev->dev.of_node, "lantiq,phy1", &phy))
                        chip->phy1 = phy & XWAY_STP_PHY_MASK;
                if (!of_property_read_u32(pdev->dev.of_node, "lantiq,phy2", &phy))
                        chip->phy2 = phy & XWAY_STP_PHY_MASK;
        }

        /* check which edge trigger we should use, default to a falling edge */
        if (!of_find_property(pdev->dev.of_node, "lantiq,rising", NULL))
                chip->edge = XWAY_STP_FALLING;

        clk = clk_get(&pdev->dev, NULL);
        if (IS_ERR(clk)) {
                dev_err(&pdev->dev, "Failed to get clock\n");
                return PTR_ERR(clk);
        }
        clk_enable(clk);

        ret = xway_stp_hw_init(chip);
        if (!ret)
                ret = devm_gpiochip_add_data(&pdev->dev, &chip->gc, chip);

        if (!ret)
                dev_info(&pdev->dev, "Init done\n");

        return ret;
}

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

static struct platform_driver xway_stp_driver = {
        .probe = xway_stp_probe,
        .driver = {
                .name = "gpio-stp-xway",
                .of_match_table = xway_stp_match,
        },
};

static int __init xway_stp_init(void)
{
        return platform_driver_register(&xway_stp_driver);
}

subsys_initcall(xway_stp_init);