// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2015-2017 Pengutronix, Uwe Kleine-König <kernel@pengutronix.de>
 */

#include <linux/gpio/consumer.h>
#include <linux/module.h>
#include <linux/mod_devicetable.h>
#include <linux/platform_device.h>

#include <linux/delay.h>

#include "siox.h"

#define DRIVER_NAME "siox-gpio"

struct siox_gpio_ddata {
        struct gpio_desc *din;
        struct gpio_desc *dout;
        struct gpio_desc *dclk;
        struct gpio_desc *dld;
};

static unsigned int siox_clkhigh_ns = 1000;
static unsigned int siox_loadhigh_ns;
static unsigned int siox_bytegap_ns;

static int siox_gpio_pushpull(struct siox_master *smaster,
                              size_t setbuf_len, const u8 setbuf[],
                              size_t getbuf_len, u8 getbuf[])
{
        struct siox_gpio_ddata *ddata = siox_master_get_devdata(smaster);
        size_t i;
        size_t cycles = max(setbuf_len, getbuf_len);

        /* reset data and clock */
        gpiod_set_value_cansleep(ddata->dout, 0);
        gpiod_set_value_cansleep(ddata->dclk, 0);

        gpiod_set_value_cansleep(ddata->dld, 1);
        ndelay(siox_loadhigh_ns);
        gpiod_set_value_cansleep(ddata->dld, 0);

        for (i = 0; i < cycles; ++i) {
                u8 set = 0, get = 0;
                size_t j;

                if (i >= cycles - setbuf_len)
                        set = setbuf[i - (cycles - setbuf_len)];

                for (j = 0; j < 8; ++j) {
                        get <<= 1;
                        if (gpiod_get_value_cansleep(ddata->din))
                                get |= 1;

                        /* DOUT is logically inverted */
                        gpiod_set_value_cansleep(ddata->dout, !(set & 0x80));
                        set <<= 1;

                        gpiod_set_value_cansleep(ddata->dclk, 1);
                        ndelay(siox_clkhigh_ns);
                        gpiod_set_value_cansleep(ddata->dclk, 0);
                }

                if (i < getbuf_len)
                        getbuf[i] = get;

                ndelay(siox_bytegap_ns);
        }

        gpiod_set_value_cansleep(ddata->dld, 1);
        ndelay(siox_loadhigh_ns);
        gpiod_set_value_cansleep(ddata->dld, 0);

        /*
         * Resetting dout isn't necessary protocol wise, but it makes the
         * signals more pretty because the dout level is deterministic between
         * cycles. Note that this only affects dout between the master and the
         * first siox device. dout for the later devices depend on the output of
         * the previous siox device.
         */
        gpiod_set_value_cansleep(ddata->dout, 0);

        return 0;
}

static int siox_gpio_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct siox_gpio_ddata *ddata;
        int ret;
        struct siox_master *smaster;

        smaster = devm_siox_master_alloc(dev, sizeof(*ddata));
        if (!smaster)
                return -ENOMEM;

        platform_set_drvdata(pdev, smaster);
        ddata = siox_master_get_devdata(smaster);

        ddata->din = devm_gpiod_get(dev, "din", GPIOD_IN);
        if (IS_ERR(ddata->din))
                return dev_err_probe(dev, PTR_ERR(ddata->din),
                                     "Failed to get din GPIO\n");

        ddata->dout = devm_gpiod_get(dev, "dout", GPIOD_OUT_LOW);
        if (IS_ERR(ddata->dout))
                return dev_err_probe(dev, PTR_ERR(ddata->dout),
                                     "Failed to get dout GPIO\n");

        ddata->dclk = devm_gpiod_get(dev, "dclk", GPIOD_OUT_LOW);
        if (IS_ERR(ddata->dclk))
                return dev_err_probe(dev, PTR_ERR(ddata->dclk),
                                     "Failed to get dclk GPIO\n");

        ddata->dld = devm_gpiod_get(dev, "dld", GPIOD_OUT_LOW);
        if (IS_ERR(ddata->dld))
                return dev_err_probe(dev, PTR_ERR(ddata->dld),
                                     "Failed to get dld GPIO\n");

        smaster->pushpull = siox_gpio_pushpull;
        /* XXX: determine automatically like spi does */
        smaster->busno = 0;

        ret = devm_siox_master_register(dev, smaster);
        if (ret)
                return dev_err_probe(dev, ret,
                                     "Failed to register siox master\n");

        return 0;
}

static const struct of_device_id siox_gpio_dt_ids[] = {
        { .compatible = "eckelmann,siox-gpio", },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, siox_gpio_dt_ids);

static struct platform_driver siox_gpio_driver = {
        .probe = siox_gpio_probe,

        .driver = {
                .name = DRIVER_NAME,
                .of_match_table = siox_gpio_dt_ids,
        },
};
module_platform_driver(siox_gpio_driver);

MODULE_AUTHOR("Uwe Kleine-Koenig <u.kleine-koenig@pengutronix.de>");
MODULE_DESCRIPTION("SIOX GPIO bus driver");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("platform:" DRIVER_NAME);