// SPDX-License-Identifier: GPL-2.0-only
/*
 * HCI based Driver for Inside Secure microread NFC Chip - i2c layer
 *
 * Copyright (C) 2013 Intel Corporation. All rights reserved.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/gpio.h>

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

#include "microread.h"

#define MICROREAD_I2C_DRIVER_NAME "microread"

#define MICROREAD_I2C_FRAME_HEADROOM 1
#define MICROREAD_I2C_FRAME_TAILROOM 1

/* framing in HCI mode */
#define MICROREAD_I2C_LLC_LEN           1
#define MICROREAD_I2C_LLC_CRC           1
#define MICROREAD_I2C_LLC_LEN_CRC       (MICROREAD_I2C_LLC_LEN + \
                                        MICROREAD_I2C_LLC_CRC)
#define MICROREAD_I2C_LLC_MIN_SIZE      (1 + MICROREAD_I2C_LLC_LEN_CRC)
#define MICROREAD_I2C_LLC_MAX_PAYLOAD   29
#define MICROREAD_I2C_LLC_MAX_SIZE      (MICROREAD_I2C_LLC_LEN_CRC + 1 + \
                                        MICROREAD_I2C_LLC_MAX_PAYLOAD)

struct microread_i2c_phy {
        struct i2c_client *i2c_dev;
        struct nfc_hci_dev *hdev;

        int hard_fault;         /*
                                 * < 0 if hardware error occured (e.g. i2c err)
                                 * and prevents normal operation.
                                 */
};

#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)

static void microread_i2c_add_len_crc(struct sk_buff *skb)
{
        int i;
        u8 crc = 0;
        int len;

        len = skb->len;
        *(u8 *)skb_push(skb, 1) = len;

        for (i = 0; i < skb->len; i++)
                crc = crc ^ skb->data[i];

        skb_put_u8(skb, crc);
}

static void microread_i2c_remove_len_crc(struct sk_buff *skb)
{
        skb_pull(skb, MICROREAD_I2C_FRAME_HEADROOM);
        skb_trim(skb, MICROREAD_I2C_FRAME_TAILROOM);
}

static int check_crc(const struct sk_buff *skb)
{
        int i;
        u8 crc = 0;

        for (i = 0; i < skb->len - 1; i++)
                crc = crc ^ skb->data[i];

        if (crc != skb->data[skb->len-1]) {
                pr_err("CRC error 0x%x != 0x%x\n", crc, skb->data[skb->len-1]);
                pr_info("%s: BAD CRC\n", __func__);
                return -EPERM;
        }

        return 0;
}

static int microread_i2c_enable(void *phy_id)
{
        return 0;
}

static void microread_i2c_disable(void *phy_id)
{
        return;
}

static int microread_i2c_write(void *phy_id, struct sk_buff *skb)
{
        int r;
        struct microread_i2c_phy *phy = phy_id;
        struct i2c_client *client = phy->i2c_dev;

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

        usleep_range(3000, 6000);

        microread_i2c_add_len_crc(skb);

        I2C_DUMP_SKB("i2c frame written", skb);

        r = i2c_master_send(client, skb->data, skb->len);

        if (r == -EREMOTEIO) {  /* Retry, chip was in standby */
                usleep_range(6000, 10000);
                r = i2c_master_send(client, skb->data, skb->len);
        }

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

        microread_i2c_remove_len_crc(skb);

        return r;
}


static int microread_i2c_read(struct microread_i2c_phy *phy,
                              struct sk_buff **skb)
{
        int r;
        u8 len;
        u8 tmp[MICROREAD_I2C_LLC_MAX_SIZE - 1];
        struct i2c_client *client = phy->i2c_dev;

        r = i2c_master_recv(client, &len, 1);
        if (r != 1) {
                nfc_err(&client->dev, "cannot read len byte\n");
                return -EREMOTEIO;
        }

        if ((len < MICROREAD_I2C_LLC_MIN_SIZE) ||
            (len > MICROREAD_I2C_LLC_MAX_SIZE)) {
                nfc_err(&client->dev, "invalid len byte\n");
                r = -EBADMSG;
                goto flush;
        }

        *skb = alloc_skb(1 + len, GFP_KERNEL);
        if (*skb == NULL) {
                r = -ENOMEM;
                goto flush;
        }

        skb_put_u8(*skb, len);

        r = i2c_master_recv(client, skb_put(*skb, len), len);
        if (r != len) {
                kfree_skb(*skb);
                return -EREMOTEIO;
        }

        I2C_DUMP_SKB("cc frame read", *skb);

        r = check_crc(*skb);
        if (r != 0) {
                kfree_skb(*skb);
                r = -EBADMSG;
                goto flush;
        }

        skb_pull(*skb, 1);
        skb_trim(*skb, (*skb)->len - MICROREAD_I2C_FRAME_TAILROOM);

        usleep_range(3000, 6000);

        return 0;

flush:
        if (i2c_master_recv(client, tmp, sizeof(tmp)) < 0)
                r = -EREMOTEIO;

        usleep_range(3000, 6000);

        return r;
}

static irqreturn_t microread_i2c_irq_thread_fn(int irq, void *phy_id)
{
        struct microread_i2c_phy *phy = phy_id;
        struct sk_buff *skb = NULL;
        int r;

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

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

        r = microread_i2c_read(phy, &skb);
        if (r == -EREMOTEIO) {
                phy->hard_fault = r;

                nfc_hci_recv_frame(phy->hdev, NULL);

                return IRQ_HANDLED;
        } else if ((r == -ENOMEM) || (r == -EBADMSG)) {
                return IRQ_HANDLED;
        }

        nfc_hci_recv_frame(phy->hdev, skb);

        return IRQ_HANDLED;
}

static const struct nfc_phy_ops i2c_phy_ops = {
        .write = microread_i2c_write,
        .enable = microread_i2c_enable,
        .disable = microread_i2c_disable,
};

static int microread_i2c_probe(struct i2c_client *client,
                               const struct i2c_device_id *id)
{
        struct microread_i2c_phy *phy;
        int r;

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

        phy = devm_kzalloc(&client->dev, sizeof(struct microread_i2c_phy),
                           GFP_KERNEL);
        if (!phy)
                return -ENOMEM;

        i2c_set_clientdata(client, phy);
        phy->i2c_dev = client;

        r = request_threaded_irq(client->irq, NULL, microread_i2c_irq_thread_fn,
                                 IRQF_TRIGGER_RISING | IRQF_ONESHOT,
                                 MICROREAD_I2C_DRIVER_NAME, phy);
        if (r) {
                nfc_err(&client->dev, "Unable to register IRQ handler\n");
                return r;
        }

        r = microread_probe(phy, &i2c_phy_ops, LLC_SHDLC_NAME,
                            MICROREAD_I2C_FRAME_HEADROOM,
                            MICROREAD_I2C_FRAME_TAILROOM,
                            MICROREAD_I2C_LLC_MAX_PAYLOAD, &phy->hdev);
        if (r < 0)
                goto err_irq;

        nfc_info(&client->dev, "Probed\n");

        return 0;

err_irq:
        free_irq(client->irq, phy);

        return r;
}

static int microread_i2c_remove(struct i2c_client *client)
{
        struct microread_i2c_phy *phy = i2c_get_clientdata(client);

        microread_remove(phy->hdev);

        free_irq(client->irq, phy);

        return 0;
}

static const struct i2c_device_id microread_i2c_id[] = {
        { MICROREAD_I2C_DRIVER_NAME, 0},
        { }
};
MODULE_DEVICE_TABLE(i2c, microread_i2c_id);

static struct i2c_driver microread_i2c_driver = {
        .driver = {
                .name = MICROREAD_I2C_DRIVER_NAME,
        },
        .probe          = microread_i2c_probe,
        .remove         = microread_i2c_remove,
        .id_table       = microread_i2c_id,
};

module_i2c_driver(microread_i2c_driver);

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