/*
 * drivers/mtd/nand/socrates_nand.c
 *
 *  Copyright © 2008 Ilya Yanok, Emcraft Systems
 *
 *
 * 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.
 *
 */

#include <linux/slab.h>
#include <linux/module.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/nand.h>
#include <linux/mtd/partitions.h>
#include <linux/of_address.h>
#include <linux/of_platform.h>
#include <linux/io.h>

#define FPGA_NAND_CMD_MASK              (0x7 << 28)
#define FPGA_NAND_CMD_COMMAND           (0x0 << 28)
#define FPGA_NAND_CMD_ADDR              (0x1 << 28)
#define FPGA_NAND_CMD_READ              (0x2 << 28)
#define FPGA_NAND_CMD_WRITE             (0x3 << 28)
#define FPGA_NAND_BUSY                  (0x1 << 15)
#define FPGA_NAND_ENABLE                (0x1 << 31)
#define FPGA_NAND_DATA_SHIFT            16

struct socrates_nand_host {
        struct nand_chip        nand_chip;
        void __iomem            *io_base;
        struct device           *dev;
};

/**
 * socrates_nand_write_buf -  write buffer to chip
 * @mtd:        MTD device structure
 * @buf:        data buffer
 * @len:        number of bytes to write
 */
static void socrates_nand_write_buf(struct mtd_info *mtd,
                const uint8_t *buf, int len)
{
        int i;
        struct nand_chip *this = mtd_to_nand(mtd);
        struct socrates_nand_host *host = nand_get_controller_data(this);

        for (i = 0; i < len; i++) {
                out_be32(host->io_base, FPGA_NAND_ENABLE |
                                FPGA_NAND_CMD_WRITE |
                                (buf[i] << FPGA_NAND_DATA_SHIFT));
        }
}

/**
 * socrates_nand_read_buf -  read chip data into buffer
 * @mtd:        MTD device structure
 * @buf:        buffer to store date
 * @len:        number of bytes to read
 */
static void socrates_nand_read_buf(struct mtd_info *mtd, uint8_t *buf, int len)
{
        int i;
        struct nand_chip *this = mtd_to_nand(mtd);
        struct socrates_nand_host *host = nand_get_controller_data(this);
        uint32_t val;

        val = FPGA_NAND_ENABLE | FPGA_NAND_CMD_READ;

        out_be32(host->io_base, val);
        for (i = 0; i < len; i++) {
                buf[i] = (in_be32(host->io_base) >>
                                FPGA_NAND_DATA_SHIFT) & 0xff;
        }
}

/**
 * socrates_nand_read_byte -  read one byte from the chip
 * @mtd:        MTD device structure
 */
static uint8_t socrates_nand_read_byte(struct mtd_info *mtd)
{
        uint8_t byte;
        socrates_nand_read_buf(mtd, &byte, sizeof(byte));
        return byte;
}

/**
 * socrates_nand_read_word -  read one word from the chip
 * @mtd:        MTD device structure
 */
static uint16_t socrates_nand_read_word(struct mtd_info *mtd)
{
        uint16_t word;
        socrates_nand_read_buf(mtd, (uint8_t *)&word, sizeof(word));
        return word;
}

/*
 * Hardware specific access to control-lines
 */
static void socrates_nand_cmd_ctrl(struct mtd_info *mtd, int cmd,
                unsigned int ctrl)
{
        struct nand_chip *nand_chip = mtd_to_nand(mtd);
        struct socrates_nand_host *host = nand_get_controller_data(nand_chip);
        uint32_t val;

        if (cmd == NAND_CMD_NONE)
                return;

        if (ctrl & NAND_CLE)
                val = FPGA_NAND_CMD_COMMAND;
        else
                val = FPGA_NAND_CMD_ADDR;

        if (ctrl & NAND_NCE)
                val |= FPGA_NAND_ENABLE;

        val |= (cmd & 0xff) << FPGA_NAND_DATA_SHIFT;

        out_be32(host->io_base, val);
}

/*
 * Read the Device Ready pin.
 */
static int socrates_nand_device_ready(struct mtd_info *mtd)
{
        struct nand_chip *nand_chip = mtd_to_nand(mtd);
        struct socrates_nand_host *host = nand_get_controller_data(nand_chip);

        if (in_be32(host->io_base) & FPGA_NAND_BUSY)
                return 0; /* busy */
        return 1;
}

/*
 * Probe for the NAND device.
 */
static int socrates_nand_probe(struct platform_device *ofdev)
{
        struct socrates_nand_host *host;
        struct mtd_info *mtd;
        struct nand_chip *nand_chip;
        int res;

        /* Allocate memory for the device structure (and zero it) */
        host = devm_kzalloc(&ofdev->dev, sizeof(*host), GFP_KERNEL);
        if (!host)
                return -ENOMEM;

        host->io_base = of_iomap(ofdev->dev.of_node, 0);
        if (host->io_base == NULL) {
                dev_err(&ofdev->dev, "ioremap failed\n");
                return -EIO;
        }

        nand_chip = &host->nand_chip;
        mtd = nand_to_mtd(nand_chip);
        host->dev = &ofdev->dev;

        /* link the private data structures */
        nand_set_controller_data(nand_chip, host);
        nand_set_flash_node(nand_chip, ofdev->dev.of_node);
        mtd->name = "socrates_nand";
        mtd->dev.parent = &ofdev->dev;

        /*should never be accessed directly */
        nand_chip->IO_ADDR_R = (void *)0xdeadbeef;
        nand_chip->IO_ADDR_W = (void *)0xdeadbeef;

        nand_chip->cmd_ctrl = socrates_nand_cmd_ctrl;
        nand_chip->read_byte = socrates_nand_read_byte;
        nand_chip->read_word = socrates_nand_read_word;
        nand_chip->write_buf = socrates_nand_write_buf;
        nand_chip->read_buf = socrates_nand_read_buf;
        nand_chip->dev_ready = socrates_nand_device_ready;

        nand_chip->ecc.mode = NAND_ECC_SOFT;    /* enable ECC */
        nand_chip->ecc.algo = NAND_ECC_HAMMING;

        /* TODO: I have no idea what real delay is. */
        nand_chip->chip_delay = 20;             /* 20us command delay time */

        dev_set_drvdata(&ofdev->dev, host);

        res = nand_scan(mtd, 1);
        if (res)
                goto out;

        res = mtd_device_register(mtd, NULL, 0);
        if (!res)
                return res;

        nand_release(mtd);

out:
        iounmap(host->io_base);
        return res;
}

/*
 * Remove a NAND device.
 */
static int socrates_nand_remove(struct platform_device *ofdev)
{
        struct socrates_nand_host *host = dev_get_drvdata(&ofdev->dev);
        struct mtd_info *mtd = nand_to_mtd(&host->nand_chip);

        nand_release(mtd);

        iounmap(host->io_base);

        return 0;
}

static const struct of_device_id socrates_nand_match[] =
{
        {
                .compatible   = "abb,socrates-nand",
        },
        {},
};

MODULE_DEVICE_TABLE(of, socrates_nand_match);

static struct platform_driver socrates_nand_driver = {
        .driver = {
                .name = "socrates_nand",
                .of_match_table = socrates_nand_match,
        },
        .probe          = socrates_nand_probe,
        .remove         = socrates_nand_remove,
};

module_platform_driver(socrates_nand_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Ilya Yanok");
MODULE_DESCRIPTION("NAND driver for Socrates board");