// SPDX-License-Identifier: GPL-2.0
/*
 * Greybus SPI library
 *
 * Copyright 2014-2016 Google Inc.
 * Copyright 2014-2016 Linaro Ltd.
 */

#include <linux/bitops.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/greybus.h>
#include <linux/spi/spi.h>

#include "spilib.h"

struct gb_spilib {
        struct gb_connection    *connection;
        struct device           *parent;
        struct spi_transfer     *first_xfer;
        struct spi_transfer     *last_xfer;
        struct spilib_ops       *ops;
        u32                     rx_xfer_offset;
        u32                     tx_xfer_offset;
        u32                     last_xfer_size;
        unsigned int            op_timeout;
        u16                     mode;
        u16                     flags;
        u32                     bits_per_word_mask;
        u8                      num_chipselect;
        u32                     min_speed_hz;
        u32                     max_speed_hz;
};

#define GB_SPI_STATE_MSG_DONE           ((void *)0)
#define GB_SPI_STATE_MSG_IDLE           ((void *)1)
#define GB_SPI_STATE_MSG_RUNNING        ((void *)2)
#define GB_SPI_STATE_OP_READY           ((void *)3)
#define GB_SPI_STATE_OP_DONE            ((void *)4)
#define GB_SPI_STATE_MSG_ERROR          ((void *)-1)

#define XFER_TIMEOUT_TOLERANCE          200

static struct spi_controller *get_controller_from_spi(struct gb_spilib *spi)
{
        return gb_connection_get_data(spi->connection);
}

static int tx_header_fit_operation(u32 tx_size, u32 count, size_t data_max)
{
        size_t headers_size;

        data_max -= sizeof(struct gb_spi_transfer_request);
        headers_size = (count + 1) * sizeof(struct gb_spi_transfer);

        return tx_size + headers_size > data_max ? 0 : 1;
}

static size_t calc_rx_xfer_size(u32 rx_size, u32 *tx_xfer_size, u32 len,
                                size_t data_max)
{
        size_t rx_xfer_size;

        data_max -= sizeof(struct gb_spi_transfer_response);

        if (rx_size + len > data_max)
                rx_xfer_size = data_max - rx_size;
        else
                rx_xfer_size = len;

        /* if this is a write_read, for symmetry read the same as write */
        if (*tx_xfer_size && rx_xfer_size > *tx_xfer_size)
                rx_xfer_size = *tx_xfer_size;
        if (*tx_xfer_size && rx_xfer_size < *tx_xfer_size)
                *tx_xfer_size = rx_xfer_size;

        return rx_xfer_size;
}

static size_t calc_tx_xfer_size(u32 tx_size, u32 count, size_t len,
                                size_t data_max)
{
        size_t headers_size;

        data_max -= sizeof(struct gb_spi_transfer_request);
        headers_size = (count + 1) * sizeof(struct gb_spi_transfer);

        if (tx_size + headers_size + len > data_max)
                return data_max - (tx_size + sizeof(struct gb_spi_transfer));

        return len;
}

static void clean_xfer_state(struct gb_spilib *spi)
{
        spi->first_xfer = NULL;
        spi->last_xfer = NULL;
        spi->rx_xfer_offset = 0;
        spi->tx_xfer_offset = 0;
        spi->last_xfer_size = 0;
        spi->op_timeout = 0;
}

static bool is_last_xfer_done(struct gb_spilib *spi)
{
        struct spi_transfer *last_xfer = spi->last_xfer;

        if ((spi->tx_xfer_offset + spi->last_xfer_size == last_xfer->len) ||
            (spi->rx_xfer_offset + spi->last_xfer_size == last_xfer->len))
                return true;

        return false;
}

static int setup_next_xfer(struct gb_spilib *spi, struct spi_message *msg)
{
        struct spi_transfer *last_xfer = spi->last_xfer;

        if (msg->state != GB_SPI_STATE_OP_DONE)
                return 0;

        /*
         * if we transferred all content of the last transfer, reset values and
         * check if this was the last transfer in the message
         */
        if (is_last_xfer_done(spi)) {
                spi->tx_xfer_offset = 0;
                spi->rx_xfer_offset = 0;
                spi->op_timeout = 0;
                if (last_xfer == list_last_entry(&msg->transfers,
                                                 struct spi_transfer,
                                                 transfer_list))
                        msg->state = GB_SPI_STATE_MSG_DONE;
                else
                        spi->first_xfer = list_next_entry(last_xfer,
                                                          transfer_list);
                return 0;
        }

        spi->first_xfer = last_xfer;
        if (last_xfer->tx_buf)
                spi->tx_xfer_offset += spi->last_xfer_size;

        if (last_xfer->rx_buf)
                spi->rx_xfer_offset += spi->last_xfer_size;

        return 0;
}

static struct spi_transfer *get_next_xfer(struct spi_transfer *xfer,
                                          struct spi_message *msg)
{
        if (xfer == list_last_entry(&msg->transfers, struct spi_transfer,
                                    transfer_list))
                return NULL;

        return list_next_entry(xfer, transfer_list);
}

/* Routines to transfer data */
static struct gb_operation *gb_spi_operation_create(struct gb_spilib *spi,
                struct gb_connection *connection, struct spi_message *msg)
{
        struct gb_spi_transfer_request *request;
        struct spi_device *dev = msg->spi;
        struct spi_transfer *xfer;
        struct gb_spi_transfer *gb_xfer;
        struct gb_operation *operation;
        u32 tx_size = 0, rx_size = 0, count = 0, xfer_len = 0, request_size;
        u32 tx_xfer_size = 0, rx_xfer_size = 0, len;
        u32 total_len = 0;
        unsigned int xfer_timeout;
        size_t data_max;
        void *tx_data;

        data_max = gb_operation_get_payload_size_max(connection);
        xfer = spi->first_xfer;

        /* Find number of transfers queued and tx/rx length in the message */

        while (msg->state != GB_SPI_STATE_OP_READY) {
                msg->state = GB_SPI_STATE_MSG_RUNNING;
                spi->last_xfer = xfer;

                if (!xfer->tx_buf && !xfer->rx_buf) {
                        dev_err(spi->parent,
                                "bufferless transfer, length %u\n", xfer->len);
                        msg->state = GB_SPI_STATE_MSG_ERROR;
                        return NULL;
                }

                tx_xfer_size = 0;
                rx_xfer_size = 0;

                if (xfer->tx_buf) {
                        len = xfer->len - spi->tx_xfer_offset;
                        if (!tx_header_fit_operation(tx_size, count, data_max))
                                break;
                        tx_xfer_size = calc_tx_xfer_size(tx_size, count,
                                                         len, data_max);
                        spi->last_xfer_size = tx_xfer_size;
                }

                if (xfer->rx_buf) {
                        len = xfer->len - spi->rx_xfer_offset;
                        rx_xfer_size = calc_rx_xfer_size(rx_size, &tx_xfer_size,
                                                         len, data_max);
                        spi->last_xfer_size = rx_xfer_size;
                }

                tx_size += tx_xfer_size;
                rx_size += rx_xfer_size;

                total_len += spi->last_xfer_size;
                count++;

                xfer = get_next_xfer(xfer, msg);
                if (!xfer || total_len >= data_max)
                        msg->state = GB_SPI_STATE_OP_READY;
        }

        /*
         * In addition to space for all message descriptors we need
         * to have enough to hold all tx data.
         */
        request_size = sizeof(*request);
        request_size += count * sizeof(*gb_xfer);
        request_size += tx_size;

        /* Response consists only of incoming data */
        operation = gb_operation_create(connection, GB_SPI_TYPE_TRANSFER,
                                        request_size, rx_size, GFP_KERNEL);
        if (!operation)
                return NULL;

        request = operation->request->payload;
        request->count = cpu_to_le16(count);
        request->mode = dev->mode;
        request->chip_select = spi_get_chipselect(dev, 0);

        gb_xfer = &request->transfers[0];
        tx_data = gb_xfer + count;      /* place tx data after last gb_xfer */

        /* Fill in the transfers array */
        xfer = spi->first_xfer;
        while (msg->state != GB_SPI_STATE_OP_DONE) {
                int xfer_delay;

                if (xfer == spi->last_xfer)
                        xfer_len = spi->last_xfer_size;
                else
                        xfer_len = xfer->len;

                /* make sure we do not timeout in a slow transfer */
                xfer_timeout = xfer_len * 8 * MSEC_PER_SEC / xfer->speed_hz;
                xfer_timeout += GB_OPERATION_TIMEOUT_DEFAULT;

                if (xfer_timeout > spi->op_timeout)
                        spi->op_timeout = xfer_timeout;

                gb_xfer->speed_hz = cpu_to_le32(xfer->speed_hz);
                gb_xfer->len = cpu_to_le32(xfer_len);
                xfer_delay = spi_delay_to_ns(&xfer->delay, xfer) / 1000;
                xfer_delay = clamp_t(u16, xfer_delay, 0, U16_MAX);
                gb_xfer->delay_usecs = cpu_to_le16(xfer_delay);
                gb_xfer->cs_change = xfer->cs_change;
                gb_xfer->bits_per_word = xfer->bits_per_word;

                /* Copy tx data */
                if (xfer->tx_buf) {
                        gb_xfer->xfer_flags |= GB_SPI_XFER_WRITE;
                        memcpy(tx_data, xfer->tx_buf + spi->tx_xfer_offset,
                               xfer_len);
                        tx_data += xfer_len;
                }

                if (xfer->rx_buf)
                        gb_xfer->xfer_flags |= GB_SPI_XFER_READ;

                if (xfer == spi->last_xfer) {
                        if (!is_last_xfer_done(spi))
                                gb_xfer->xfer_flags |= GB_SPI_XFER_INPROGRESS;
                        msg->state = GB_SPI_STATE_OP_DONE;
                        continue;
                }

                gb_xfer++;
                xfer = get_next_xfer(xfer, msg);
        }

        msg->actual_length += total_len;

        return operation;
}

static void gb_spi_decode_response(struct gb_spilib *spi,
                                   struct spi_message *msg,
                                   struct gb_spi_transfer_response *response)
{
        struct spi_transfer *xfer = spi->first_xfer;
        void *rx_data = response->data;
        u32 xfer_len;

        while (xfer) {
                /* Copy rx data */
                if (xfer->rx_buf) {
                        if (xfer == spi->first_xfer)
                                xfer_len = xfer->len - spi->rx_xfer_offset;
                        else if (xfer == spi->last_xfer)
                                xfer_len = spi->last_xfer_size;
                        else
                                xfer_len = xfer->len;

                        memcpy(xfer->rx_buf + spi->rx_xfer_offset, rx_data,
                               xfer_len);
                        rx_data += xfer_len;
                }

                if (xfer == spi->last_xfer)
                        break;

                xfer = list_next_entry(xfer, transfer_list);
        }
}

static int gb_spi_transfer_one_message(struct spi_controller *ctlr,
                                       struct spi_message *msg)
{
        struct gb_spilib *spi = spi_controller_get_devdata(ctlr);
        struct gb_connection *connection = spi->connection;
        struct gb_spi_transfer_response *response;
        struct gb_operation *operation;
        int ret = 0;

        spi->first_xfer = list_first_entry_or_null(&msg->transfers,
                                                   struct spi_transfer,
                                                   transfer_list);
        if (!spi->first_xfer) {
                ret = -ENOMEM;
                goto out;
        }

        msg->state = GB_SPI_STATE_MSG_IDLE;

        while (msg->state != GB_SPI_STATE_MSG_DONE &&
               msg->state != GB_SPI_STATE_MSG_ERROR) {
                operation = gb_spi_operation_create(spi, connection, msg);
                if (!operation) {
                        msg->state = GB_SPI_STATE_MSG_ERROR;
                        ret = -EINVAL;
                        continue;
                }

                ret = gb_operation_request_send_sync_timeout(operation,
                                                             spi->op_timeout);
                if (!ret) {
                        response = operation->response->payload;
                        if (response)
                                gb_spi_decode_response(spi, msg, response);
                } else {
                        dev_err(spi->parent,
                                "transfer operation failed: %d\n", ret);
                        msg->state = GB_SPI_STATE_MSG_ERROR;
                }

                gb_operation_put(operation);
                setup_next_xfer(spi, msg);
        }

out:
        msg->status = ret;
        clean_xfer_state(spi);
        spi_finalize_current_message(ctlr);

        return ret;
}

static int gb_spi_prepare_transfer_hardware(struct spi_controller *ctlr)
{
        struct gb_spilib *spi = spi_controller_get_devdata(ctlr);

        return spi->ops->prepare_transfer_hardware(spi->parent);
}

static int gb_spi_unprepare_transfer_hardware(struct spi_controller *ctlr)
{
        struct gb_spilib *spi = spi_controller_get_devdata(ctlr);

        spi->ops->unprepare_transfer_hardware(spi->parent);

        return 0;
}

static int gb_spi_setup(struct spi_device *spi)
{
        /* Nothing to do for now */
        return 0;
}

static void gb_spi_cleanup(struct spi_device *spi)
{
        /* Nothing to do for now */
}

/* Routines to get controller information */

/*
 * Map Greybus spi mode bits/flags/bpw into Linux ones.
 * All bits are same for now and so these macro's return same values.
 */
#define gb_spi_mode_map(mode) mode
#define gb_spi_flags_map(flags) flags

static int gb_spi_get_master_config(struct gb_spilib *spi)
{
        struct gb_spi_master_config_response response;
        u16 mode, flags;
        int ret;

        ret = gb_operation_sync(spi->connection, GB_SPI_TYPE_MASTER_CONFIG,
                                NULL, 0, &response, sizeof(response));
        if (ret < 0)
                return ret;

        mode = le16_to_cpu(response.mode);
        spi->mode = gb_spi_mode_map(mode);

        flags = le16_to_cpu(response.flags);
        spi->flags = gb_spi_flags_map(flags);

        spi->bits_per_word_mask = le32_to_cpu(response.bits_per_word_mask);
        spi->num_chipselect = response.num_chipselect;

        spi->min_speed_hz = le32_to_cpu(response.min_speed_hz);
        spi->max_speed_hz = le32_to_cpu(response.max_speed_hz);

        return 0;
}

static int gb_spi_setup_device(struct gb_spilib *spi, u8 cs)
{
        struct spi_controller *ctlr = get_controller_from_spi(spi);
        struct gb_spi_device_config_request request;
        struct gb_spi_device_config_response response;
        struct spi_board_info spi_board = { {0} };
        struct spi_device *spidev;
        int ret;
        u8 dev_type;

        request.chip_select = cs;

        ret = gb_operation_sync(spi->connection, GB_SPI_TYPE_DEVICE_CONFIG,
                                &request, sizeof(request),
                                &response, sizeof(response));
        if (ret < 0)
                return ret;

        dev_type = response.device_type;

        if (dev_type == GB_SPI_SPI_DEV)
                strscpy(spi_board.modalias, "spidev",
                        sizeof(spi_board.modalias));
        else if (dev_type == GB_SPI_SPI_NOR)
                strscpy(spi_board.modalias, "spi-nor",
                        sizeof(spi_board.modalias));
        else if (dev_type == GB_SPI_SPI_MODALIAS)
                memcpy(spi_board.modalias, response.name,
                       sizeof(spi_board.modalias));
        else
                return -EINVAL;

        spi_board.mode          = le16_to_cpu(response.mode);
        spi_board.bus_num       = ctlr->bus_num;
        spi_board.chip_select   = cs;
        spi_board.max_speed_hz  = le32_to_cpu(response.max_speed_hz);

        spidev = spi_new_device(ctlr, &spi_board);
        if (!spidev)
                return -EINVAL;

        return 0;
}

int gb_spilib_master_init(struct gb_connection *connection, struct device *dev,
                          struct spilib_ops *ops)
{
        struct gb_spilib *spi;
        struct spi_controller *ctlr;
        int ret;
        u8 i;

        /* Allocate host with space for data */
        ctlr = spi_alloc_host(dev, sizeof(*spi));
        if (!ctlr) {
                dev_err(dev, "cannot alloc SPI host\n");
                return -ENOMEM;
        }

        spi = spi_controller_get_devdata(ctlr);
        spi->connection = connection;
        gb_connection_set_data(connection, ctlr);
        spi->parent = dev;
        spi->ops = ops;

        /* get controller configuration */
        ret = gb_spi_get_master_config(spi);
        if (ret)
                goto exit_spi_put;

        ctlr->bus_num = -1; /* Allow spi-core to allocate it dynamically */
        ctlr->num_chipselect = spi->num_chipselect;
        ctlr->mode_bits = spi->mode;
        ctlr->flags = spi->flags;
        ctlr->bits_per_word_mask = spi->bits_per_word_mask;

        /* Attach methods */
        ctlr->cleanup = gb_spi_cleanup;
        ctlr->setup = gb_spi_setup;
        ctlr->transfer_one_message = gb_spi_transfer_one_message;

        if (ops && ops->prepare_transfer_hardware) {
                ctlr->prepare_transfer_hardware =
                        gb_spi_prepare_transfer_hardware;
        }

        if (ops && ops->unprepare_transfer_hardware) {
                ctlr->unprepare_transfer_hardware =
                        gb_spi_unprepare_transfer_hardware;
        }

        ctlr->auto_runtime_pm = true;

        ret = spi_register_controller(ctlr);
        if (ret < 0)
                goto exit_spi_put;

        /* now, fetch the devices configuration */
        for (i = 0; i < spi->num_chipselect; i++) {
                ret = gb_spi_setup_device(spi, i);
                if (ret < 0) {
                        dev_err(dev, "failed to allocate spi device %d: %d\n",
                                i, ret);
                        goto exit_spi_unregister;
                }
        }

        return 0;

exit_spi_put:
        spi_controller_put(ctlr);

        return ret;

exit_spi_unregister:
        spi_unregister_controller(ctlr);

        return ret;
}
EXPORT_SYMBOL_GPL(gb_spilib_master_init);

void gb_spilib_master_exit(struct gb_connection *connection)
{
        struct spi_controller *ctlr = gb_connection_get_data(connection);

        spi_unregister_controller(ctlr);
}
EXPORT_SYMBOL_GPL(gb_spilib_master_exit);

MODULE_DESCRIPTION("Greybus SPI library");
MODULE_LICENSE("GPL v2");