/*
 * I2C Link Layer for ST21NFCA HCI based Driver
 * Copyright (C) 2014  STMicroelectronics SAS. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see <http://www.gnu.org/licenses/>.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/crc-ccitt.h>
#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/gpio.h>
#include <linux/of_irq.h>
#include <linux/of_gpio.h>
#include <linux/miscdevice.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/nfc.h>
#include <linux/firmware.h>
#include <linux/platform_data/st21nfca.h>
#include <asm/unaligned.h>

#include <net/nfc/hci.h>
#include <net/nfc/llc.h>
#include <net/nfc/nfc.h>

#include "st21nfca.h"

/*
 * Every frame starts with ST21NFCA_SOF_EOF and ends with ST21NFCA_SOF_EOF.
 * Because ST21NFCA_SOF_EOF is a possible data value, there is a mecanism
 * called byte stuffing has been introduced.
 *
 * if byte == ST21NFCA_SOF_EOF or ST21NFCA_ESCAPE_BYTE_STUFFING
 * - insert ST21NFCA_ESCAPE_BYTE_STUFFING (escape byte)
 * - xor byte with ST21NFCA_BYTE_STUFFING_MASK
 */
#define ST21NFCA_SOF_EOF                0x7e
#define ST21NFCA_BYTE_STUFFING_MASK     0x20
#define ST21NFCA_ESCAPE_BYTE_STUFFING   0x7d

/* SOF + 00 */
#define ST21NFCA_FRAME_HEADROOM                 2

/* 2 bytes crc + EOF */
#define ST21NFCA_FRAME_TAILROOM 3
#define IS_START_OF_FRAME(buf) (buf[0] == ST21NFCA_SOF_EOF && \
                                buf[1] == 0)

#define ST21NFCA_HCI_I2C_DRIVER_NAME "st21nfca_hci_i2c"

static struct i2c_device_id st21nfca_hci_i2c_id_table[] = {
        {ST21NFCA_HCI_DRIVER_NAME, 0},
        {}
};

MODULE_DEVICE_TABLE(i2c, st21nfca_hci_i2c_id_table);

struct st21nfca_i2c_phy {
        struct i2c_client *i2c_dev;
        struct nfc_hci_dev *hdev;

        unsigned int gpio_ena;
        unsigned int irq_polarity;

        struct sk_buff *pending_skb;
        int current_read_len;
        /*
         * crc might have fail because i2c macro
         * is disable due to other interface activity
         */
        int crc_trials;

        int powered;
        int run_mode;

        /*
         * < 0 if hardware error occured (e.g. i2c err)
         * and prevents normal operation.
         */
        int hard_fault;
        struct mutex phy_lock;
};
static u8 len_seq[] = { 16, 24, 12, 29 };
static u16 wait_tab[] = { 2, 3, 5, 15, 20, 40};

#define I2C_DUMP_SKB(info, skb)                                 \
do {                                                            \
        pr_debug("%s:\n", info);                                \
        print_hex_dump(KERN_DEBUG, "i2c: ", DUMP_PREFIX_OFFSET, \
                       16, 1, (skb)->data, (skb)->len, 0);      \
} while (0)

/*
 * In order to get the CLF in a known state we generate an internal reboot
 * using a proprietary command.
 * Once the reboot is completed, we expect to receive a ST21NFCA_SOF_EOF
 * fill buffer.
 */
static int st21nfca_hci_platform_init(struct st21nfca_i2c_phy *phy)
{
        u16 wait_reboot[] = { 50, 300, 1000 };
        char reboot_cmd[] = { 0x7E, 0x66, 0x48, 0xF6, 0x7E };
        u8 tmp[ST21NFCA_HCI_LLC_MAX_SIZE];
        int i, r = -1;

        for (i = 0; i < ARRAY_SIZE(wait_reboot) && r < 0; i++) {
                r = i2c_master_send(phy->i2c_dev, reboot_cmd,
                                    sizeof(reboot_cmd));
                if (r < 0)
                        msleep(wait_reboot[i]);
        }
        if (r < 0)
                return r;

        /* CLF is spending about 20ms to do an internal reboot */
        msleep(20);
        r = -1;
        for (i = 0; i < ARRAY_SIZE(wait_reboot) && r < 0; i++) {
                r = i2c_master_recv(phy->i2c_dev, tmp,
                                    ST21NFCA_HCI_LLC_MAX_SIZE);
                if (r < 0)
                        msleep(wait_reboot[i]);
        }
        if (r < 0)
                return r;

        for (i = 0; i < ST21NFCA_HCI_LLC_MAX_SIZE &&
                tmp[i] == ST21NFCA_SOF_EOF; i++)
                ;

        if (r != ST21NFCA_HCI_LLC_MAX_SIZE)
                return -ENODEV;

        usleep_range(1000, 1500);
        return 0;
}

static int st21nfca_hci_i2c_enable(void *phy_id)
{
        struct st21nfca_i2c_phy *phy = phy_id;

        gpio_set_value(phy->gpio_ena, 1);
        phy->powered = 1;
        phy->run_mode = ST21NFCA_HCI_MODE;

        usleep_range(10000, 15000);

        return 0;
}

static void st21nfca_hci_i2c_disable(void *phy_id)
{
        struct st21nfca_i2c_phy *phy = phy_id;

        pr_info("\n");
        gpio_set_value(phy->gpio_ena, 0);

        phy->powered = 0;
}

static void st21nfca_hci_add_len_crc(struct sk_buff *skb)
{
        u16 crc;
        u8 tmp;

        *skb_push(skb, 1) = 0;

        crc = crc_ccitt(0xffff, skb->data, skb->len);
        crc = ~crc;

        tmp = crc & 0x00ff;
        *skb_put(skb, 1) = tmp;

        tmp = (crc >> 8) & 0x00ff;
        *skb_put(skb, 1) = tmp;
}

static void st21nfca_hci_remove_len_crc(struct sk_buff *skb)
{
        skb_pull(skb, ST21NFCA_FRAME_HEADROOM);
        skb_trim(skb, skb->len - ST21NFCA_FRAME_TAILROOM);
}

/*
 * Writing a frame must not return the number of written bytes.
 * It must return either zero for success, or <0 for error.
 * In addition, it must not alter the skb
 */
static int st21nfca_hci_i2c_write(void *phy_id, struct sk_buff *skb)
{
        int r = -1, i, j;
        struct st21nfca_i2c_phy *phy = phy_id;
        struct i2c_client *client = phy->i2c_dev;
        u8 tmp[ST21NFCA_HCI_LLC_MAX_SIZE * 2];

        I2C_DUMP_SKB("st21nfca_hci_i2c_write", skb);


        if (phy->hard_fault != 0)
                return phy->hard_fault;

        /*
         * Compute CRC before byte stuffing computation on frame
         * Note st21nfca_hci_add_len_crc is doing a byte stuffing
         * on its own value
         */
        st21nfca_hci_add_len_crc(skb);

        /* add ST21NFCA_SOF_EOF on tail */
        *skb_put(skb, 1) = ST21NFCA_SOF_EOF;
        /* add ST21NFCA_SOF_EOF on head */
        *skb_push(skb, 1) = ST21NFCA_SOF_EOF;

        /*
         * Compute byte stuffing
         * if byte == ST21NFCA_SOF_EOF or ST21NFCA_ESCAPE_BYTE_STUFFING
         * insert ST21NFCA_ESCAPE_BYTE_STUFFING (escape byte)
         * xor byte with ST21NFCA_BYTE_STUFFING_MASK
         */
        tmp[0] = skb->data[0];
        for (i = 1, j = 1; i < skb->len - 1; i++, j++) {
                if (skb->data[i] == ST21NFCA_SOF_EOF
                    || skb->data[i] == ST21NFCA_ESCAPE_BYTE_STUFFING) {
                        tmp[j] = ST21NFCA_ESCAPE_BYTE_STUFFING;
                        j++;
                        tmp[j] = skb->data[i] ^ ST21NFCA_BYTE_STUFFING_MASK;
                } else {
                        tmp[j] = skb->data[i];
                }
        }
        tmp[j] = skb->data[i];
        j++;

        /*
         * Manage sleep mode
         * Try 3 times to send data with delay between each
         */
        mutex_lock(&phy->phy_lock);
        for (i = 0; i < ARRAY_SIZE(wait_tab) && r < 0; i++) {
                r = i2c_master_send(client, tmp, j);
                if (r < 0)
                        msleep(wait_tab[i]);
        }
        mutex_unlock(&phy->phy_lock);

        if (r >= 0) {
                if (r != j)
                        r = -EREMOTEIO;
                else
                        r = 0;
        }

        st21nfca_hci_remove_len_crc(skb);

        return r;
}

static int get_frame_size(u8 *buf, int buflen)
{
        int len = 0;

        if (buf[len + 1] == ST21NFCA_SOF_EOF)
                return 0;

        for (len = 1; len < buflen && buf[len] != ST21NFCA_SOF_EOF; len++)
                ;

        return len;
}

static int check_crc(u8 *buf, int buflen)
{
        u16 crc;

        crc = crc_ccitt(0xffff, buf, buflen - 2);
        crc = ~crc;

        if (buf[buflen - 2] != (crc & 0xff) || buf[buflen - 1] != (crc >> 8)) {
                pr_err(ST21NFCA_HCI_DRIVER_NAME
                       ": CRC error 0x%x != 0x%x 0x%x\n", crc, buf[buflen - 1],
                       buf[buflen - 2]);

                pr_info(DRIVER_DESC ": %s : BAD CRC\n", __func__);
                print_hex_dump(KERN_DEBUG, "crc: ", DUMP_PREFIX_NONE,
                               16, 2, buf, buflen, false);
                return -EPERM;
        }
        return 0;
}

/*
 * Prepare received data for upper layer.
 * Received data include byte stuffing, crc and sof/eof
 * which is not usable by hci part.
 * returns:
 * frame size without sof/eof, header and byte stuffing
 * -EBADMSG : frame was incorrect and discarded
 */
static int st21nfca_hci_i2c_repack(struct sk_buff *skb)
{
        int i, j, r, size;

        if (skb->len < 1 || (skb->len > 1 && skb->data[1] != 0))
                return -EBADMSG;

        size = get_frame_size(skb->data, skb->len);
        if (size > 0) {
                skb_trim(skb, size);
                /* remove ST21NFCA byte stuffing for upper layer */
                for (i = 1, j = 0; i < skb->len; i++) {
                        if (skb->data[i + j] ==
                                        (u8) ST21NFCA_ESCAPE_BYTE_STUFFING) {
                                skb->data[i] = skb->data[i + j + 1]
                                                | ST21NFCA_BYTE_STUFFING_MASK;
                                i++;
                                j++;
                        }
                        skb->data[i] = skb->data[i + j];
                }
                /* remove byte stuffing useless byte */
                skb_trim(skb, i - j);
                /* remove ST21NFCA_SOF_EOF from head */
                skb_pull(skb, 1);

                r = check_crc(skb->data, skb->len);
                if (r != 0) {
                        i = 0;
                        return -EBADMSG;
                }

                /* remove headbyte */
                skb_pull(skb, 1);
                /* remove crc. Byte Stuffing is already removed here */
                skb_trim(skb, skb->len - 2);
                return skb->len;
        }
        return 0;
}

/*
 * Reads an shdlc frame and returns it in a newly allocated sk_buff. Guarantees
 * that i2c bus will be flushed and that next read will start on a new frame.
 * returned skb contains only LLC header and payload.
 * returns:
 * frame size : if received frame is complete (find ST21NFCA_SOF_EOF at
 * end of read)
 * -EAGAIN : if received frame is incomplete (not find ST21NFCA_SOF_EOF
 * at end of read)
 * -EREMOTEIO : i2c read error (fatal)
 * -EBADMSG : frame was incorrect and discarded
 * (value returned from st21nfca_hci_i2c_repack)
 * -EIO : if no ST21NFCA_SOF_EOF is found after reaching
 * the read length end sequence
 */
static int st21nfca_hci_i2c_read(struct st21nfca_i2c_phy *phy,
                                 struct sk_buff *skb)
{
        int r, i;
        u8 len;
        u8 buf[ST21NFCA_HCI_LLC_MAX_PAYLOAD];
        struct i2c_client *client = phy->i2c_dev;

        if (phy->current_read_len < ARRAY_SIZE(len_seq)) {
                len = len_seq[phy->current_read_len];

                /*
                 * Add retry mecanism
                 * Operation on I2C interface may fail in case of operation on
                 * RF or SWP interface
                 */
                r = 0;
                mutex_lock(&phy->phy_lock);
                for (i = 0; i < ARRAY_SIZE(wait_tab) && r <= 0; i++) {
                        r = i2c_master_recv(client, buf, len);
                        if (r < 0)
                                msleep(wait_tab[i]);
                }
                mutex_unlock(&phy->phy_lock);

                if (r != len) {
                        phy->current_read_len = 0;
                        return -EREMOTEIO;
                }

                /*
                 * The first read sequence does not start with SOF.
                 * Data is corrupeted so we drop it.
                 */
                if (!phy->current_read_len && !IS_START_OF_FRAME(buf)) {
                        skb_trim(skb, 0);
                        phy->current_read_len = 0;
                        return -EIO;
                } else if (phy->current_read_len && IS_START_OF_FRAME(buf)) {
                        /*
                         * Previous frame transmission was interrupted and
                         * the frame got repeated.
                         * Received frame start with ST21NFCA_SOF_EOF + 00.
                         */
                        skb_trim(skb, 0);
                        phy->current_read_len = 0;
                }

                memcpy(skb_put(skb, len), buf, len);

                if (skb->data[skb->len - 1] == ST21NFCA_SOF_EOF) {
                        phy->current_read_len = 0;
                        return st21nfca_hci_i2c_repack(skb);
                }
                phy->current_read_len++;
                return -EAGAIN;
        }
        return -EIO;
}

/*
 * Reads an shdlc frame from the chip. This is not as straightforward as it
 * seems. The frame format is data-crc, and corruption can occur anywhere
 * while transiting on i2c bus, such that we could read an invalid data.
 * The tricky case is when we read a corrupted data or crc. We must detect
 * this here in order to determine that data can be transmitted to the hci
 * core. This is the reason why we check the crc here.
 * The CLF will repeat a frame until we send a RR on that frame.
 *
 * On ST21NFCA, IRQ goes in idle when read starts. As no size information are
 * available in the incoming data, other IRQ might come. Every IRQ will trigger
 * a read sequence with different length and will fill the current frame.
 * The reception is complete once we reach a ST21NFCA_SOF_EOF.
 */
static irqreturn_t st21nfca_hci_irq_thread_fn(int irq, void *phy_id)
{
        struct st21nfca_i2c_phy *phy = phy_id;
        struct i2c_client *client;

        int r;

        if (!phy || irq != phy->i2c_dev->irq) {
                WARN_ON_ONCE(1);
                return IRQ_NONE;
        }

        client = phy->i2c_dev;
        dev_dbg(&client->dev, "IRQ\n");

        if (phy->hard_fault != 0)
                return IRQ_HANDLED;

        r = st21nfca_hci_i2c_read(phy, phy->pending_skb);
        if (r == -EREMOTEIO) {
                phy->hard_fault = r;

                nfc_hci_recv_frame(phy->hdev, NULL);

                return IRQ_HANDLED;
        } else if (r == -EAGAIN || r == -EIO) {
                return IRQ_HANDLED;
        } else if (r == -EBADMSG && phy->crc_trials < ARRAY_SIZE(wait_tab)) {
                /*
                 * With ST21NFCA, only one interface (I2C, RF or SWP)
                 * may be active at a time.
                 * Having incorrect crc is usually due to i2c macrocell
                 * deactivation in the middle of a transmission.
                 * It may generate corrupted data on i2c.
                 * We give sometime to get i2c back.
                 * The complete frame will be repeated.
                 */
                msleep(wait_tab[phy->crc_trials]);
                phy->crc_trials++;
                phy->current_read_len = 0;
                kfree_skb(phy->pending_skb);
        } else if (r > 0) {
                /*
                 * We succeeded to read data from the CLF and
                 * data is valid.
                 * Reset counter.
                 */
                nfc_hci_recv_frame(phy->hdev, phy->pending_skb);
                phy->crc_trials = 0;
        } else {
                kfree_skb(phy->pending_skb);
        }

        phy->pending_skb = alloc_skb(ST21NFCA_HCI_LLC_MAX_SIZE * 2, GFP_KERNEL);
        if (phy->pending_skb == NULL) {
                phy->hard_fault = -ENOMEM;
                nfc_hci_recv_frame(phy->hdev, NULL);
        }

        return IRQ_HANDLED;
}

static struct nfc_phy_ops i2c_phy_ops = {
        .write = st21nfca_hci_i2c_write,
        .enable = st21nfca_hci_i2c_enable,
        .disable = st21nfca_hci_i2c_disable,
};

#ifdef CONFIG_OF
static int st21nfca_hci_i2c_of_request_resources(struct i2c_client *client)
{
        struct st21nfca_i2c_phy *phy = i2c_get_clientdata(client);
        struct device_node *pp;
        int gpio;
        int r;

        pp = client->dev.of_node;
        if (!pp)
                return -ENODEV;

        /* Get GPIO from device tree */
        gpio = of_get_named_gpio(pp, "enable-gpios", 0);
        if (gpio < 0) {
                nfc_err(&client->dev, "Failed to retrieve enable-gpios from device tree\n");
                return gpio;
        }

        /* GPIO request and configuration */
        r = devm_gpio_request_one(&client->dev, gpio, GPIOF_OUT_INIT_HIGH,
                                  "clf_enable");
        if (r) {
                nfc_err(&client->dev, "Failed to request enable pin\n");
                return r;
        }

        phy->gpio_ena = gpio;

        phy->irq_polarity = irq_get_trigger_type(client->irq);

        return 0;
}
#else
static int st21nfca_hci_i2c_of_request_resources(struct i2c_client *client)
{
        return -ENODEV;
}
#endif

static int st21nfca_hci_i2c_request_resources(struct i2c_client *client)
{
        struct st21nfca_nfc_platform_data *pdata;
        struct st21nfca_i2c_phy *phy = i2c_get_clientdata(client);
        int r;

        pdata = client->dev.platform_data;
        if (pdata == NULL) {
                nfc_err(&client->dev, "No platform data\n");
                return -EINVAL;
        }

        /* store for later use */
        phy->gpio_ena = pdata->gpio_ena;
        phy->irq_polarity = pdata->irq_polarity;

        if (phy->gpio_ena > 0) {
                r = devm_gpio_request_one(&client->dev, phy->gpio_ena,
                                          GPIOF_OUT_INIT_HIGH, "clf_enable");
                if (r) {
                        pr_err("%s : ena gpio_request failed\n", __FILE__);
                        return r;
                }
        }

        return 0;
}

static int st21nfca_hci_i2c_probe(struct i2c_client *client,
                                  const struct i2c_device_id *id)
{
        struct st21nfca_i2c_phy *phy;
        struct st21nfca_nfc_platform_data *pdata;
        int r;

        dev_dbg(&client->dev, "%s\n", __func__);
        dev_dbg(&client->dev, "IRQ: %d\n", client->irq);

        if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
                nfc_err(&client->dev, "Need I2C_FUNC_I2C\n");
                return -ENODEV;
        }

        phy = devm_kzalloc(&client->dev, sizeof(struct st21nfca_i2c_phy),
                           GFP_KERNEL);
        if (!phy) {
                nfc_err(&client->dev,
                        "Cannot allocate memory for st21nfca i2c phy.\n");
                return -ENOMEM;
        }

        phy->i2c_dev = client;
        phy->pending_skb = alloc_skb(ST21NFCA_HCI_LLC_MAX_SIZE * 2, GFP_KERNEL);
        if (phy->pending_skb == NULL)
                return -ENOMEM;

        phy->current_read_len = 0;
        phy->crc_trials = 0;
        mutex_init(&phy->phy_lock);
        i2c_set_clientdata(client, phy);

        pdata = client->dev.platform_data;
        if (!pdata && client->dev.of_node) {
                r = st21nfca_hci_i2c_of_request_resources(client);
                if (r) {
                        nfc_err(&client->dev, "No platform data\n");
                        return r;
                }
        } else if (pdata) {
                r = st21nfca_hci_i2c_request_resources(client);
                if (r) {
                        nfc_err(&client->dev, "Cannot get platform resources\n");
                        return r;
                }
        } else {
                nfc_err(&client->dev, "st21nfca platform resources not available\n");
                return -ENODEV;
        }

        r = st21nfca_hci_platform_init(phy);
        if (r < 0) {
                nfc_err(&client->dev, "Unable to reboot st21nfca\n");
                return r;
        }

        r = devm_request_threaded_irq(&client->dev, client->irq, NULL,
                                st21nfca_hci_irq_thread_fn,
                                phy->irq_polarity | IRQF_ONESHOT,
                                ST21NFCA_HCI_DRIVER_NAME, phy);
        if (r < 0) {
                nfc_err(&client->dev, "Unable to register IRQ handler\n");
                return r;
        }

        return st21nfca_hci_probe(phy, &i2c_phy_ops, LLC_SHDLC_NAME,
                               ST21NFCA_FRAME_HEADROOM, ST21NFCA_FRAME_TAILROOM,
                               ST21NFCA_HCI_LLC_MAX_PAYLOAD, &phy->hdev);
}

static int st21nfca_hci_i2c_remove(struct i2c_client *client)
{
        struct st21nfca_i2c_phy *phy = i2c_get_clientdata(client);

        dev_dbg(&client->dev, "%s\n", __func__);

        st21nfca_hci_remove(phy->hdev);

        if (phy->powered)
                st21nfca_hci_i2c_disable(phy);

        return 0;
}

#ifdef CONFIG_OF
static const struct of_device_id of_st21nfca_i2c_match[] = {
        { .compatible = "st,st21nfca_i2c", },
        {}
};
MODULE_DEVICE_TABLE(of, of_st21nfca_i2c_match);
#endif

static struct i2c_driver st21nfca_hci_i2c_driver = {
        .driver = {
                .owner = THIS_MODULE,
                .name = ST21NFCA_HCI_I2C_DRIVER_NAME,
                .of_match_table = of_match_ptr(of_st21nfca_i2c_match),
        },
        .probe = st21nfca_hci_i2c_probe,
        .id_table = st21nfca_hci_i2c_id_table,
        .remove = st21nfca_hci_i2c_remove,
};

module_i2c_driver(st21nfca_hci_i2c_driver);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION(DRIVER_DESC);