/*
 * Designware SPI core controller driver (refer pxa2xx_spi.c)
 *
 * Copyright (c) 2009, Intel Corporation.
 *
 * 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.
 */

#include <linux/dma-mapping.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/highmem.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/spi/spi.h>
#include <linux/gpio.h>

#include "spi-dw.h"

#ifdef CONFIG_DEBUG_FS
#include <linux/debugfs.h>
#endif

/* Slave spi_dev related */
struct chip_data {
        u8 cs;                  /* chip select pin */
        u8 tmode;               /* TR/TO/RO/EEPROM */
        u8 type;                /* SPI/SSP/MicroWire */

        u8 poll_mode;           /* 1 means use poll mode */

        u8 enable_dma;
        u16 clk_div;            /* baud rate divider */
        u32 speed_hz;           /* baud rate */
        void (*cs_control)(u32 command);
};

#ifdef CONFIG_DEBUG_FS
#define SPI_REGS_BUFSIZE        1024
static ssize_t dw_spi_show_regs(struct file *file, char __user *user_buf,
                size_t count, loff_t *ppos)
{
        struct dw_spi *dws = file->private_data;
        char *buf;
        u32 len = 0;
        ssize_t ret;

        buf = kzalloc(SPI_REGS_BUFSIZE, GFP_KERNEL);
        if (!buf)
                return 0;

        len += snprintf(buf + len, SPI_REGS_BUFSIZE - len,
                        "%s registers:\n", dev_name(&dws->master->dev));
        len += snprintf(buf + len, SPI_REGS_BUFSIZE - len,
                        "=================================\n");
        len += snprintf(buf + len, SPI_REGS_BUFSIZE - len,
                        "CTRL0: \t\t0x%08x\n", dw_readl(dws, DW_SPI_CTRL0));
        len += snprintf(buf + len, SPI_REGS_BUFSIZE - len,
                        "CTRL1: \t\t0x%08x\n", dw_readl(dws, DW_SPI_CTRL1));
        len += snprintf(buf + len, SPI_REGS_BUFSIZE - len,
                        "SSIENR: \t0x%08x\n", dw_readl(dws, DW_SPI_SSIENR));
        len += snprintf(buf + len, SPI_REGS_BUFSIZE - len,
                        "SER: \t\t0x%08x\n", dw_readl(dws, DW_SPI_SER));
        len += snprintf(buf + len, SPI_REGS_BUFSIZE - len,
                        "BAUDR: \t\t0x%08x\n", dw_readl(dws, DW_SPI_BAUDR));
        len += snprintf(buf + len, SPI_REGS_BUFSIZE - len,
                        "TXFTLR: \t0x%08x\n", dw_readl(dws, DW_SPI_TXFLTR));
        len += snprintf(buf + len, SPI_REGS_BUFSIZE - len,
                        "RXFTLR: \t0x%08x\n", dw_readl(dws, DW_SPI_RXFLTR));
        len += snprintf(buf + len, SPI_REGS_BUFSIZE - len,
                        "TXFLR: \t\t0x%08x\n", dw_readl(dws, DW_SPI_TXFLR));
        len += snprintf(buf + len, SPI_REGS_BUFSIZE - len,
                        "RXFLR: \t\t0x%08x\n", dw_readl(dws, DW_SPI_RXFLR));
        len += snprintf(buf + len, SPI_REGS_BUFSIZE - len,
                        "SR: \t\t0x%08x\n", dw_readl(dws, DW_SPI_SR));
        len += snprintf(buf + len, SPI_REGS_BUFSIZE - len,
                        "IMR: \t\t0x%08x\n", dw_readl(dws, DW_SPI_IMR));
        len += snprintf(buf + len, SPI_REGS_BUFSIZE - len,
                        "ISR: \t\t0x%08x\n", dw_readl(dws, DW_SPI_ISR));
        len += snprintf(buf + len, SPI_REGS_BUFSIZE - len,
                        "DMACR: \t\t0x%08x\n", dw_readl(dws, DW_SPI_DMACR));
        len += snprintf(buf + len, SPI_REGS_BUFSIZE - len,
                        "DMATDLR: \t0x%08x\n", dw_readl(dws, DW_SPI_DMATDLR));
        len += snprintf(buf + len, SPI_REGS_BUFSIZE - len,
                        "DMARDLR: \t0x%08x\n", dw_readl(dws, DW_SPI_DMARDLR));
        len += snprintf(buf + len, SPI_REGS_BUFSIZE - len,
                        "=================================\n");

        ret = simple_read_from_buffer(user_buf, count, ppos, buf, len);
        kfree(buf);
        return ret;
}

static const struct file_operations dw_spi_regs_ops = {
        .owner          = THIS_MODULE,
        .open           = simple_open,
        .read           = dw_spi_show_regs,
        .llseek         = default_llseek,
};

static int dw_spi_debugfs_init(struct dw_spi *dws)
{
        dws->debugfs = debugfs_create_dir("dw_spi", NULL);
        if (!dws->debugfs)
                return -ENOMEM;

        debugfs_create_file("registers", S_IFREG | S_IRUGO,
                dws->debugfs, (void *)dws, &dw_spi_regs_ops);
        return 0;
}

static void dw_spi_debugfs_remove(struct dw_spi *dws)
{
        debugfs_remove_recursive(dws->debugfs);
}

#else
static inline int dw_spi_debugfs_init(struct dw_spi *dws)
{
        return 0;
}

static inline void dw_spi_debugfs_remove(struct dw_spi *dws)
{
}
#endif /* CONFIG_DEBUG_FS */

static void dw_spi_set_cs(struct spi_device *spi, bool enable)
{
        struct dw_spi *dws = spi_master_get_devdata(spi->master);
        struct chip_data *chip = spi_get_ctldata(spi);

        /* Chip select logic is inverted from spi_set_cs() */
        if (chip && chip->cs_control)
                chip->cs_control(!enable);

        if (!enable)
                dw_writel(dws, DW_SPI_SER, BIT(spi->chip_select));
}

/* Return the max entries we can fill into tx fifo */
static inline u32 tx_max(struct dw_spi *dws)
{
        u32 tx_left, tx_room, rxtx_gap;

        tx_left = (dws->tx_end - dws->tx) / dws->n_bytes;
        tx_room = dws->fifo_len - dw_readl(dws, DW_SPI_TXFLR);

        /*
         * Another concern is about the tx/rx mismatch, we
         * though to use (dws->fifo_len - rxflr - txflr) as
         * one maximum value for tx, but it doesn't cover the
         * data which is out of tx/rx fifo and inside the
         * shift registers. So a control from sw point of
         * view is taken.
         */
        rxtx_gap =  ((dws->rx_end - dws->rx) - (dws->tx_end - dws->tx))
                        / dws->n_bytes;

        return min3(tx_left, tx_room, (u32) (dws->fifo_len - rxtx_gap));
}

/* Return the max entries we should read out of rx fifo */
static inline u32 rx_max(struct dw_spi *dws)
{
        u32 rx_left = (dws->rx_end - dws->rx) / dws->n_bytes;

        return min_t(u32, rx_left, dw_readl(dws, DW_SPI_RXFLR));
}

static void dw_writer(struct dw_spi *dws)
{
        u32 max = tx_max(dws);
        u16 txw = 0;

        while (max--) {
                /* Set the tx word if the transfer's original "tx" is not null */
                if (dws->tx_end - dws->len) {
                        if (dws->n_bytes == 1)
                                txw = *(u8 *)(dws->tx);
                        else
                                txw = *(u16 *)(dws->tx);
                }
                dw_write_io_reg(dws, DW_SPI_DR, txw);
                dws->tx += dws->n_bytes;
        }
}

static void dw_reader(struct dw_spi *dws)
{
        u32 max = rx_max(dws);
        u16 rxw;

        while (max--) {
                rxw = dw_read_io_reg(dws, DW_SPI_DR);
                /* Care rx only if the transfer's original "rx" is not null */
                if (dws->rx_end - dws->len) {
                        if (dws->n_bytes == 1)
                                *(u8 *)(dws->rx) = rxw;
                        else
                                *(u16 *)(dws->rx) = rxw;
                }
                dws->rx += dws->n_bytes;
        }
}

static void int_error_stop(struct dw_spi *dws, const char *msg)
{
        spi_reset_chip(dws);

        dev_err(&dws->master->dev, "%s\n", msg);
        dws->master->cur_msg->status = -EIO;
        spi_finalize_current_transfer(dws->master);
}

static irqreturn_t interrupt_transfer(struct dw_spi *dws)
{
        u16 irq_status = dw_readl(dws, DW_SPI_ISR);

        /* Error handling */
        if (irq_status & (SPI_INT_TXOI | SPI_INT_RXOI | SPI_INT_RXUI)) {
                dw_readl(dws, DW_SPI_ICR);
                int_error_stop(dws, "interrupt_transfer: fifo overrun/underrun");
                return IRQ_HANDLED;
        }

        dw_reader(dws);
        if (dws->rx_end == dws->rx) {
                spi_mask_intr(dws, SPI_INT_TXEI);
                spi_finalize_current_transfer(dws->master);
                return IRQ_HANDLED;
        }
        if (irq_status & SPI_INT_TXEI) {
                spi_mask_intr(dws, SPI_INT_TXEI);
                dw_writer(dws);
                /* Enable TX irq always, it will be disabled when RX finished */
                spi_umask_intr(dws, SPI_INT_TXEI);
        }

        return IRQ_HANDLED;
}

static irqreturn_t dw_spi_irq(int irq, void *dev_id)
{
        struct spi_master *master = dev_id;
        struct dw_spi *dws = spi_master_get_devdata(master);
        u16 irq_status = dw_readl(dws, DW_SPI_ISR) & 0x3f;

        if (!irq_status)
                return IRQ_NONE;

        if (!master->cur_msg) {
                spi_mask_intr(dws, SPI_INT_TXEI);
                return IRQ_HANDLED;
        }

        return dws->transfer_handler(dws);
}

/* Must be called inside pump_transfers() */
static int poll_transfer(struct dw_spi *dws)
{
        do {
                dw_writer(dws);
                dw_reader(dws);
                cpu_relax();
        } while (dws->rx_end > dws->rx);

        return 0;
}

static int dw_spi_transfer_one(struct spi_master *master,
                struct spi_device *spi, struct spi_transfer *transfer)
{
        struct dw_spi *dws = spi_master_get_devdata(master);
        struct chip_data *chip = spi_get_ctldata(spi);
        u8 imask = 0;
        u16 txlevel = 0;
        u16 clk_div;
        u32 cr0;
        int ret;

        dws->dma_mapped = 0;

        dws->tx = (void *)transfer->tx_buf;
        dws->tx_end = dws->tx + transfer->len;
        dws->rx = transfer->rx_buf;
        dws->rx_end = dws->rx + transfer->len;
        dws->len = transfer->len;

        spi_enable_chip(dws, 0);

        /* Handle per transfer options for bpw and speed */
        if (transfer->speed_hz != chip->speed_hz) {
                /* clk_div doesn't support odd number */
                clk_div = (dws->max_freq / transfer->speed_hz + 1) & 0xfffe;

                chip->speed_hz = transfer->speed_hz;
                chip->clk_div = clk_div;

                spi_set_clk(dws, chip->clk_div);
        }
        if (transfer->bits_per_word == 8) {
                dws->n_bytes = 1;
                dws->dma_width = 1;
        } else if (transfer->bits_per_word == 16) {
                dws->n_bytes = 2;
                dws->dma_width = 2;
        } else {
                return -EINVAL;
        }
        /* Default SPI mode is SCPOL = 0, SCPH = 0 */
        cr0 = (transfer->bits_per_word - 1)
                | (chip->type << SPI_FRF_OFFSET)
                | (spi->mode << SPI_MODE_OFFSET)
                | (chip->tmode << SPI_TMOD_OFFSET);

        /*
         * Adjust transfer mode if necessary. Requires platform dependent
         * chipselect mechanism.
         */
        if (chip->cs_control) {
                if (dws->rx && dws->tx)
                        chip->tmode = SPI_TMOD_TR;
                else if (dws->rx)
                        chip->tmode = SPI_TMOD_RO;
                else
                        chip->tmode = SPI_TMOD_TO;

                cr0 &= ~SPI_TMOD_MASK;
                cr0 |= (chip->tmode << SPI_TMOD_OFFSET);
        }

        dw_writel(dws, DW_SPI_CTRL0, cr0);

        /* Check if current transfer is a DMA transaction */
        if (master->can_dma && master->can_dma(master, spi, transfer))
                dws->dma_mapped = master->cur_msg_mapped;

        /* For poll mode just disable all interrupts */
        spi_mask_intr(dws, 0xff);

        /*
         * Interrupt mode
         * we only need set the TXEI IRQ, as TX/RX always happen syncronizely
         */
        if (dws->dma_mapped) {
                ret = dws->dma_ops->dma_setup(dws, transfer);
                if (ret < 0) {
                        spi_enable_chip(dws, 1);
                        return ret;
                }
        } else if (!chip->poll_mode) {
                txlevel = min_t(u16, dws->fifo_len / 2, dws->len / dws->n_bytes);
                dw_writel(dws, DW_SPI_TXFLTR, txlevel);

                /* Set the interrupt mask */
                imask |= SPI_INT_TXEI | SPI_INT_TXOI |
                         SPI_INT_RXUI | SPI_INT_RXOI;
                spi_umask_intr(dws, imask);

                dws->transfer_handler = interrupt_transfer;
        }

        spi_enable_chip(dws, 1);

        if (dws->dma_mapped) {
                ret = dws->dma_ops->dma_transfer(dws, transfer);
                if (ret < 0)
                        return ret;
        }

        if (chip->poll_mode)
                return poll_transfer(dws);

        return 1;
}

static void dw_spi_handle_err(struct spi_master *master,
                struct spi_message *msg)
{
        struct dw_spi *dws = spi_master_get_devdata(master);

        if (dws->dma_mapped)
                dws->dma_ops->dma_stop(dws);

        spi_reset_chip(dws);
}

/* This may be called twice for each spi dev */
static int dw_spi_setup(struct spi_device *spi)
{
        struct dw_spi_chip *chip_info = NULL;
        struct chip_data *chip;
        int ret;

        /* Only alloc on first setup */
        chip = spi_get_ctldata(spi);
        if (!chip) {
                chip = kzalloc(sizeof(struct chip_data), GFP_KERNEL);
                if (!chip)
                        return -ENOMEM;
                spi_set_ctldata(spi, chip);
        }

        /*
         * Protocol drivers may change the chip settings, so...
         * if chip_info exists, use it
         */
        chip_info = spi->controller_data;

        /* chip_info doesn't always exist */
        if (chip_info) {
                if (chip_info->cs_control)
                        chip->cs_control = chip_info->cs_control;

                chip->poll_mode = chip_info->poll_mode;
                chip->type = chip_info->type;
        }

        chip->tmode = SPI_TMOD_TR;

        if (gpio_is_valid(spi->cs_gpio)) {
                ret = gpio_direction_output(spi->cs_gpio,
                                !(spi->mode & SPI_CS_HIGH));
                if (ret)
                        return ret;
        }

        return 0;
}

static void dw_spi_cleanup(struct spi_device *spi)
{
        struct chip_data *chip = spi_get_ctldata(spi);

        kfree(chip);
        spi_set_ctldata(spi, NULL);
}

/* Restart the controller, disable all interrupts, clean rx fifo */
static void spi_hw_init(struct device *dev, struct dw_spi *dws)
{
        spi_reset_chip(dws);

        /*
         * Try to detect the FIFO depth if not set by interface driver,
         * the depth could be from 2 to 256 from HW spec
         */
        if (!dws->fifo_len) {
                u32 fifo;

                for (fifo = 1; fifo < 256; fifo++) {
                        dw_writel(dws, DW_SPI_TXFLTR, fifo);
                        if (fifo != dw_readl(dws, DW_SPI_TXFLTR))
                                break;
                }
                dw_writel(dws, DW_SPI_TXFLTR, 0);

                dws->fifo_len = (fifo == 1) ? 0 : fifo;
                dev_dbg(dev, "Detected FIFO size: %u bytes\n", dws->fifo_len);
        }
}

int dw_spi_add_host(struct device *dev, struct dw_spi *dws)
{
        struct spi_master *master;
        int ret;

        BUG_ON(dws == NULL);

        master = spi_alloc_master(dev, 0);
        if (!master)
                return -ENOMEM;

        dws->master = master;
        dws->type = SSI_MOTO_SPI;
        dws->dma_inited = 0;
        dws->dma_addr = (dma_addr_t)(dws->paddr + DW_SPI_DR);
        snprintf(dws->name, sizeof(dws->name), "dw_spi%d", dws->bus_num);

        ret = request_irq(dws->irq, dw_spi_irq, IRQF_SHARED, dws->name, master);
        if (ret < 0) {
                dev_err(dev, "can not get IRQ\n");
                goto err_free_master;
        }

        master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_LOOP;
        master->bits_per_word_mask = SPI_BPW_MASK(8) | SPI_BPW_MASK(16);
        master->bus_num = dws->bus_num;
        master->num_chipselect = dws->num_cs;
        master->setup = dw_spi_setup;
        master->cleanup = dw_spi_cleanup;
        master->set_cs = dw_spi_set_cs;
        master->transfer_one = dw_spi_transfer_one;
        master->handle_err = dw_spi_handle_err;
        master->max_speed_hz = dws->max_freq;
        master->dev.of_node = dev->of_node;

        /* Basic HW init */
        spi_hw_init(dev, dws);

        if (dws->dma_ops && dws->dma_ops->dma_init) {
                ret = dws->dma_ops->dma_init(dws);
                if (ret) {
                        dev_warn(dev, "DMA init failed\n");
                        dws->dma_inited = 0;
                } else {
                        master->can_dma = dws->dma_ops->can_dma;
                }
        }

        spi_master_set_devdata(master, dws);
        ret = devm_spi_register_master(dev, master);
        if (ret) {
                dev_err(&master->dev, "problem registering spi master\n");
                goto err_dma_exit;
        }

        dw_spi_debugfs_init(dws);
        return 0;

err_dma_exit:
        if (dws->dma_ops && dws->dma_ops->dma_exit)
                dws->dma_ops->dma_exit(dws);
        spi_enable_chip(dws, 0);
        free_irq(dws->irq, master);
err_free_master:
        spi_master_put(master);
        return ret;
}
EXPORT_SYMBOL_GPL(dw_spi_add_host);

void dw_spi_remove_host(struct dw_spi *dws)
{
        dw_spi_debugfs_remove(dws);

        if (dws->dma_ops && dws->dma_ops->dma_exit)
                dws->dma_ops->dma_exit(dws);

        spi_shutdown_chip(dws);

        free_irq(dws->irq, dws->master);
}
EXPORT_SYMBOL_GPL(dw_spi_remove_host);

int dw_spi_suspend_host(struct dw_spi *dws)
{
        int ret;

        ret = spi_master_suspend(dws->master);
        if (ret)
                return ret;

        spi_shutdown_chip(dws);
        return 0;
}
EXPORT_SYMBOL_GPL(dw_spi_suspend_host);

int dw_spi_resume_host(struct dw_spi *dws)
{
        int ret;

        spi_hw_init(&dws->master->dev, dws);
        ret = spi_master_resume(dws->master);
        if (ret)
                dev_err(&dws->master->dev, "fail to start queue (%d)\n", ret);
        return ret;
}
EXPORT_SYMBOL_GPL(dw_spi_resume_host);

MODULE_AUTHOR("Feng Tang <feng.tang@intel.com>");
MODULE_DESCRIPTION("Driver for DesignWare SPI controller core");
MODULE_LICENSE("GPL v2");