/*
 * Copyright (C) 2013  Intel Corporation. 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 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, write to the Free Software Foundation, Inc.,
 * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
 *
 */

#define pr_fmt(fmt) "nci_spi: %s: " fmt, __func__

#include <linux/module.h>

#include <linux/export.h>
#include <linux/spi/spi.h>
#include <linux/crc-ccitt.h>
#include <net/nfc/nci_core.h>

#define NCI_SPI_ACK_SHIFT               6
#define NCI_SPI_MSB_PAYLOAD_MASK        0x3F

#define NCI_SPI_SEND_TIMEOUT    (NCI_CMD_TIMEOUT > NCI_DATA_TIMEOUT ? \
                                        NCI_CMD_TIMEOUT : NCI_DATA_TIMEOUT)

#define NCI_SPI_DIRECT_WRITE    0x01
#define NCI_SPI_DIRECT_READ     0x02

#define ACKNOWLEDGE_NONE        0
#define ACKNOWLEDGE_ACK         1
#define ACKNOWLEDGE_NACK        2

#define CRC_INIT                0xFFFF

static int __nci_spi_send(struct nci_spi *nspi, struct sk_buff *skb,
                          int cs_change)
{
        struct spi_message m;
        struct spi_transfer t;

        memset(&t, 0, sizeof(struct spi_transfer));
        /* a NULL skb means we just want the SPI chip select line to raise */
        if (skb) {
                t.tx_buf = skb->data;
                t.len = skb->len;
        } else {
                /* still set tx_buf non NULL to make the driver happy */
                t.tx_buf = &t;
                t.len = 0;
        }
        t.cs_change = cs_change;
        t.delay_usecs = nspi->xfer_udelay;
        t.speed_hz = nspi->xfer_speed_hz;

        spi_message_init(&m);
        spi_message_add_tail(&t, &m);

        return spi_sync(nspi->spi, &m);
}

int nci_spi_send(struct nci_spi *nspi,
                 struct completion *write_handshake_completion,
                 struct sk_buff *skb)
{
        unsigned int payload_len = skb->len;
        unsigned char *hdr;
        int ret;
        long completion_rc;

        /* add the NCI SPI header to the start of the buffer */
        hdr = skb_push(skb, NCI_SPI_HDR_LEN);
        hdr[0] = NCI_SPI_DIRECT_WRITE;
        hdr[1] = nspi->acknowledge_mode;
        hdr[2] = payload_len >> 8;
        hdr[3] = payload_len & 0xFF;

        if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
                u16 crc;

                crc = crc_ccitt(CRC_INIT, skb->data, skb->len);
                skb_put_u8(skb, crc >> 8);
                skb_put_u8(skb, crc & 0xFF);
        }

        if (write_handshake_completion) {
                /* Trick SPI driver to raise chip select */
                ret = __nci_spi_send(nspi, NULL, 1);
                if (ret)
                        goto done;

                /* wait for NFC chip hardware handshake to complete */
                if (wait_for_completion_timeout(write_handshake_completion,
                                                msecs_to_jiffies(1000)) == 0) {
                        ret = -ETIME;
                        goto done;
                }
        }

        ret = __nci_spi_send(nspi, skb, 0);
        if (ret != 0 || nspi->acknowledge_mode == NCI_SPI_CRC_DISABLED)
                goto done;

        reinit_completion(&nspi->req_completion);
        completion_rc = wait_for_completion_interruptible_timeout(
                                                        &nspi->req_completion,
                                                        NCI_SPI_SEND_TIMEOUT);

        if (completion_rc <= 0 || nspi->req_result == ACKNOWLEDGE_NACK)
                ret = -EIO;

done:
        kfree_skb(skb);

        return ret;
}
EXPORT_SYMBOL_GPL(nci_spi_send);

/* ---- Interface to NCI SPI drivers ---- */

/**
 * nci_spi_allocate_spi - allocate a new nci spi
 *
 * @spi: SPI device
 * @acknowledge_mode: Acknowledge mode used by the NFC device
 * @delay: delay between transactions in us
 * @ndev: nci dev to send incoming nci frames to
 */
struct nci_spi *nci_spi_allocate_spi(struct spi_device *spi,
                                     u8 acknowledge_mode, unsigned int delay,
                                     struct nci_dev *ndev)
{
        struct nci_spi *nspi;

        nspi = devm_kzalloc(&spi->dev, sizeof(struct nci_spi), GFP_KERNEL);
        if (!nspi)
                return NULL;

        nspi->acknowledge_mode = acknowledge_mode;
        nspi->xfer_udelay = delay;
        /* Use controller max SPI speed by default */
        nspi->xfer_speed_hz = 0;
        nspi->spi = spi;
        nspi->ndev = ndev;
        init_completion(&nspi->req_completion);

        return nspi;
}
EXPORT_SYMBOL_GPL(nci_spi_allocate_spi);

static int send_acknowledge(struct nci_spi *nspi, u8 acknowledge)
{
        struct sk_buff *skb;
        unsigned char *hdr;
        u16 crc;
        int ret;

        skb = nci_skb_alloc(nspi->ndev, 0, GFP_KERNEL);

        /* add the NCI SPI header to the start of the buffer */
        hdr = skb_push(skb, NCI_SPI_HDR_LEN);
        hdr[0] = NCI_SPI_DIRECT_WRITE;
        hdr[1] = NCI_SPI_CRC_ENABLED;
        hdr[2] = acknowledge << NCI_SPI_ACK_SHIFT;
        hdr[3] = 0;

        crc = crc_ccitt(CRC_INIT, skb->data, skb->len);
        skb_put_u8(skb, crc >> 8);
        skb_put_u8(skb, crc & 0xFF);

        ret = __nci_spi_send(nspi, skb, 0);

        kfree_skb(skb);

        return ret;
}

static struct sk_buff *__nci_spi_read(struct nci_spi *nspi)
{
        struct sk_buff *skb;
        struct spi_message m;
        unsigned char req[2], resp_hdr[2];
        struct spi_transfer tx, rx;
        unsigned short rx_len = 0;
        int ret;

        spi_message_init(&m);

        memset(&tx, 0, sizeof(struct spi_transfer));
        req[0] = NCI_SPI_DIRECT_READ;
        req[1] = nspi->acknowledge_mode;
        tx.tx_buf = req;
        tx.len = 2;
        tx.cs_change = 0;
        tx.speed_hz = nspi->xfer_speed_hz;
        spi_message_add_tail(&tx, &m);

        memset(&rx, 0, sizeof(struct spi_transfer));
        rx.rx_buf = resp_hdr;
        rx.len = 2;
        rx.cs_change = 1;
        rx.speed_hz = nspi->xfer_speed_hz;
        spi_message_add_tail(&rx, &m);

        ret = spi_sync(nspi->spi, &m);
        if (ret)
                return NULL;

        if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED)
                rx_len = ((resp_hdr[0] & NCI_SPI_MSB_PAYLOAD_MASK) << 8) +
                                resp_hdr[1] + NCI_SPI_CRC_LEN;
        else
                rx_len = (resp_hdr[0] << 8) | resp_hdr[1];

        skb = nci_skb_alloc(nspi->ndev, rx_len, GFP_KERNEL);
        if (!skb)
                return NULL;

        spi_message_init(&m);

        memset(&rx, 0, sizeof(struct spi_transfer));
        rx.rx_buf = skb_put(skb, rx_len);
        rx.len = rx_len;
        rx.cs_change = 0;
        rx.delay_usecs = nspi->xfer_udelay;
        rx.speed_hz = nspi->xfer_speed_hz;
        spi_message_add_tail(&rx, &m);

        ret = spi_sync(nspi->spi, &m);
        if (ret)
                goto receive_error;

        if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
                *(u8 *)skb_push(skb, 1) = resp_hdr[1];
                *(u8 *)skb_push(skb, 1) = resp_hdr[0];
        }

        return skb;

receive_error:
        kfree_skb(skb);

        return NULL;
}

static int nci_spi_check_crc(struct sk_buff *skb)
{
        u16 crc_data = (skb->data[skb->len - 2] << 8) |
                        skb->data[skb->len - 1];
        int ret;

        ret = (crc_ccitt(CRC_INIT, skb->data, skb->len - NCI_SPI_CRC_LEN)
                        == crc_data);

        skb_trim(skb, skb->len - NCI_SPI_CRC_LEN);

        return ret;
}

static u8 nci_spi_get_ack(struct sk_buff *skb)
{
        u8 ret;

        ret = skb->data[0] >> NCI_SPI_ACK_SHIFT;

        /* Remove NFCC part of the header: ACK, NACK and MSB payload len */
        skb_pull(skb, 2);

        return ret;
}

/**
 * nci_spi_read - read frame from NCI SPI drivers
 *
 * @nspi: The nci spi
 * Context: can sleep
 *
 * This call may only be used from a context that may sleep.  The sleep
 * is non-interruptible, and has no timeout.
 *
 * It returns an allocated skb containing the frame on success, or NULL.
 */
struct sk_buff *nci_spi_read(struct nci_spi *nspi)
{
        struct sk_buff *skb;

        /* Retrieve frame from SPI */
        skb = __nci_spi_read(nspi);
        if (!skb)
                goto done;

        if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
                if (!nci_spi_check_crc(skb)) {
                        send_acknowledge(nspi, ACKNOWLEDGE_NACK);
                        goto done;
                }

                /* In case of acknowledged mode: if ACK or NACK received,
                 * unblock completion of latest frame sent.
                 */
                nspi->req_result = nci_spi_get_ack(skb);
                if (nspi->req_result)
                        complete(&nspi->req_completion);
        }

        /* If there is no payload (ACK/NACK only frame),
         * free the socket buffer
         */
        if (!skb->len) {
                kfree_skb(skb);
                skb = NULL;
                goto done;
        }

        if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED)
                send_acknowledge(nspi, ACKNOWLEDGE_ACK);

done:

        return skb;
}
EXPORT_SYMBOL_GPL(nci_spi_read);

MODULE_LICENSE("GPL");