/*
 * This file is provided under a dual BSD/GPLv2 license.  When using or
 * redistributing this file, you may do so under either license.
 *
 * Copyright(c) 2012 Intel Corporation. All rights reserved.
 *
 * GPL LICENSE SUMMARY
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License 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, write to the Free Software
 * Foundation, Inc., 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
 * The full GNU General Public License is included in this distribution
 * in the file called LICENSE.GPL.
 *
 * BSD LICENSE
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   * Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in
 *     the documentation and/or other materials provided with the
 *     distribution.
 *   * Neither the name of Intel Corporation nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 *  Supports the SMBus Message Transport (SMT) in the Intel Atom Processor
 *  S12xx Product Family.
 *
 *  Features supported by this driver:
 *  Hardware PEC                     yes
 *  Block buffer                     yes
 *  Block process call transaction   no
 *  Slave mode                       no
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/pci.h>
#include <linux/kernel.h>
#include <linux/stddef.h>
#include <linux/completion.h>
#include <linux/dma-mapping.h>
#include <linux/i2c.h>
#include <linux/acpi.h>
#include <linux/interrupt.h>

#include <asm-generic/io-64-nonatomic-lo-hi.h>

/* PCI Address Constants */
#define SMBBAR          0

/* PCI DIDs for the Intel SMBus Message Transport (SMT) Devices */
#define PCI_DEVICE_ID_INTEL_S1200_SMT0  0x0c59
#define PCI_DEVICE_ID_INTEL_S1200_SMT1  0x0c5a
#define PCI_DEVICE_ID_INTEL_AVOTON_SMT  0x1f15

#define ISMT_DESC_ENTRIES       32      /* number of descriptor entries */
#define ISMT_MAX_RETRIES        3       /* number of SMBus retries to attempt */

/* Hardware Descriptor Constants - Control Field */
#define ISMT_DESC_CWRL  0x01    /* Command/Write Length */
#define ISMT_DESC_BLK   0X04    /* Perform Block Transaction */
#define ISMT_DESC_FAIR  0x08    /* Set fairness flag upon successful arbit. */
#define ISMT_DESC_PEC   0x10    /* Packet Error Code */
#define ISMT_DESC_I2C   0x20    /* I2C Enable */
#define ISMT_DESC_INT   0x40    /* Interrupt */
#define ISMT_DESC_SOE   0x80    /* Stop On Error */

/* Hardware Descriptor Constants - Status Field */
#define ISMT_DESC_SCS   0x01    /* Success */
#define ISMT_DESC_DLTO  0x04    /* Data Low Time Out */
#define ISMT_DESC_NAK   0x08    /* NAK Received */
#define ISMT_DESC_CRC   0x10    /* CRC Error */
#define ISMT_DESC_CLTO  0x20    /* Clock Low Time Out */
#define ISMT_DESC_COL   0x40    /* Collisions */
#define ISMT_DESC_LPR   0x80    /* Large Packet Received */

/* Macros */
#define ISMT_DESC_ADDR_RW(addr, rw) (((addr) << 1) | (rw))

/* iSMT General Register address offsets (SMBBAR + <addr>) */
#define ISMT_GR_GCTRL           0x000   /* General Control */
#define ISMT_GR_SMTICL          0x008   /* SMT Interrupt Cause Location */
#define ISMT_GR_ERRINTMSK       0x010   /* Error Interrupt Mask */
#define ISMT_GR_ERRAERMSK       0x014   /* Error AER Mask */
#define ISMT_GR_ERRSTS          0x018   /* Error Status */
#define ISMT_GR_ERRINFO         0x01c   /* Error Information */

/* iSMT Master Registers */
#define ISMT_MSTR_MDBA          0x100   /* Master Descriptor Base Address */
#define ISMT_MSTR_MCTRL         0x108   /* Master Control */
#define ISMT_MSTR_MSTS          0x10c   /* Master Status */
#define ISMT_MSTR_MDS           0x110   /* Master Descriptor Size */
#define ISMT_MSTR_RPOLICY       0x114   /* Retry Policy */

/* iSMT Miscellaneous Registers */
#define ISMT_SPGT       0x300   /* SMBus PHY Global Timing */

/* General Control Register (GCTRL) bit definitions */
#define ISMT_GCTRL_TRST 0x04    /* Target Reset */
#define ISMT_GCTRL_KILL 0x08    /* Kill */
#define ISMT_GCTRL_SRST 0x40    /* Soft Reset */

/* Master Control Register (MCTRL) bit definitions */
#define ISMT_MCTRL_SS   0x01            /* Start/Stop */
#define ISMT_MCTRL_MEIE 0x10            /* Master Error Interrupt Enable */
#define ISMT_MCTRL_FMHP 0x00ff0000      /* Firmware Master Head Ptr (FMHP) */

/* Master Status Register (MSTS) bit definitions */
#define ISMT_MSTS_HMTP  0xff0000        /* HW Master Tail Pointer (HMTP) */
#define ISMT_MSTS_MIS   0x20            /* Master Interrupt Status (MIS) */
#define ISMT_MSTS_MEIS  0x10            /* Master Error Int Status (MEIS) */
#define ISMT_MSTS_IP    0x01            /* In Progress */

/* Master Descriptor Size (MDS) bit definitions */
#define ISMT_MDS_MASK   0xff    /* Master Descriptor Size mask (MDS) */

/* SMBus PHY Global Timing Register (SPGT) bit definitions */
#define ISMT_SPGT_SPD_MASK      0xc0000000      /* SMBus Speed mask */
#define ISMT_SPGT_SPD_80K       0x00            /* 80 kHz */
#define ISMT_SPGT_SPD_100K      (0x1 << 30)     /* 100 kHz */
#define ISMT_SPGT_SPD_400K      (0x2 << 30)     /* 400 kHz */
#define ISMT_SPGT_SPD_1M        (0x3 << 30)     /* 1 MHz */


/* MSI Control Register (MSICTL) bit definitions */
#define ISMT_MSICTL_MSIE        0x01    /* MSI Enable */

/* iSMT Hardware Descriptor */
struct ismt_desc {
        u8 tgtaddr_rw;  /* target address & r/w bit */
        u8 wr_len_cmd;  /* write length in bytes or a command */
        u8 rd_len;      /* read length */
        u8 control;     /* control bits */
        u8 status;      /* status bits */
        u8 retry;       /* collision retry and retry count */
        u8 rxbytes;     /* received bytes */
        u8 txbytes;     /* transmitted bytes */
        u32 dptr_low;   /* lower 32 bit of the data pointer */
        u32 dptr_high;  /* upper 32 bit of the data pointer */
} __packed;

struct ismt_priv {
        struct i2c_adapter adapter;
        void *smba;                             /* PCI BAR */
        struct pci_dev *pci_dev;
        struct ismt_desc *hw;                   /* descriptor virt base addr */
        dma_addr_t io_rng_dma;                  /* descriptor HW base addr */
        u8 head;                                /* ring buffer head pointer */
        struct completion cmp;                  /* interrupt completion */
        u8 dma_buffer[I2C_SMBUS_BLOCK_MAX + 1]; /* temp R/W data buffer */
        bool using_msi;                         /* type of interrupt flag */
};

/**
 * ismt_ids - PCI device IDs supported by this driver
 */
static DEFINE_PCI_DEVICE_TABLE(ismt_ids) = {
        { PCI_DEVICE(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_S1200_SMT0) },
        { PCI_DEVICE(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_S1200_SMT1) },
        { PCI_DEVICE(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_AVOTON_SMT) },
        { 0, }
};

MODULE_DEVICE_TABLE(pci, ismt_ids);

/* Bus speed control bits for slow debuggers - refer to the docs for usage */
static unsigned int bus_speed;
module_param(bus_speed, uint, S_IRUGO);
MODULE_PARM_DESC(bus_speed, "Bus Speed in kHz (0 = BIOS default)");

/**
 * __ismt_desc_dump() - dump the contents of a specific descriptor
 */
static void __ismt_desc_dump(struct device *dev, const struct ismt_desc *desc)
{

        dev_dbg(dev, "Descriptor struct:  %p\n", desc);
        dev_dbg(dev, "\ttgtaddr_rw=0x%02X\n", desc->tgtaddr_rw);
        dev_dbg(dev, "\twr_len_cmd=0x%02X\n", desc->wr_len_cmd);
        dev_dbg(dev, "\trd_len=    0x%02X\n", desc->rd_len);
        dev_dbg(dev, "\tcontrol=   0x%02X\n", desc->control);
        dev_dbg(dev, "\tstatus=    0x%02X\n", desc->status);
        dev_dbg(dev, "\tretry=     0x%02X\n", desc->retry);
        dev_dbg(dev, "\trxbytes=   0x%02X\n", desc->rxbytes);
        dev_dbg(dev, "\ttxbytes=   0x%02X\n", desc->txbytes);
        dev_dbg(dev, "\tdptr_low=  0x%08X\n", desc->dptr_low);
        dev_dbg(dev, "\tdptr_high= 0x%08X\n", desc->dptr_high);
}
/**
 * ismt_desc_dump() - dump the contents of a descriptor for debug purposes
 * @priv: iSMT private data
 */
static void ismt_desc_dump(struct ismt_priv *priv)
{
        struct device *dev = &priv->pci_dev->dev;
        struct ismt_desc *desc = &priv->hw[priv->head];

        dev_dbg(dev, "Dump of the descriptor struct:  0x%X\n", priv->head);
        __ismt_desc_dump(dev, desc);
}

/**
 * ismt_gen_reg_dump() - dump the iSMT General Registers
 * @priv: iSMT private data
 */
static void ismt_gen_reg_dump(struct ismt_priv *priv)
{
        struct device *dev = &priv->pci_dev->dev;

        dev_dbg(dev, "Dump of the iSMT General Registers\n");
        dev_dbg(dev, "  GCTRL.... : (0x%p)=0x%X\n",
                priv->smba + ISMT_GR_GCTRL,
                readl(priv->smba + ISMT_GR_GCTRL));
        dev_dbg(dev, "  SMTICL... : (0x%p)=0x%016llX\n",
                priv->smba + ISMT_GR_SMTICL,
                (long long unsigned int)readq(priv->smba + ISMT_GR_SMTICL));
        dev_dbg(dev, "  ERRINTMSK : (0x%p)=0x%X\n",
                priv->smba + ISMT_GR_ERRINTMSK,
                readl(priv->smba + ISMT_GR_ERRINTMSK));
        dev_dbg(dev, "  ERRAERMSK : (0x%p)=0x%X\n",
                priv->smba + ISMT_GR_ERRAERMSK,
                readl(priv->smba + ISMT_GR_ERRAERMSK));
        dev_dbg(dev, "  ERRSTS... : (0x%p)=0x%X\n",
                priv->smba + ISMT_GR_ERRSTS,
                readl(priv->smba + ISMT_GR_ERRSTS));
        dev_dbg(dev, "  ERRINFO.. : (0x%p)=0x%X\n",
                priv->smba + ISMT_GR_ERRINFO,
                readl(priv->smba + ISMT_GR_ERRINFO));
}

/**
 * ismt_mstr_reg_dump() - dump the iSMT Master Registers
 * @priv: iSMT private data
 */
static void ismt_mstr_reg_dump(struct ismt_priv *priv)
{
        struct device *dev = &priv->pci_dev->dev;

        dev_dbg(dev, "Dump of the iSMT Master Registers\n");
        dev_dbg(dev, "  MDBA..... : (0x%p)=0x%016llX\n",
                priv->smba + ISMT_MSTR_MDBA,
                (long long unsigned int)readq(priv->smba + ISMT_MSTR_MDBA));
        dev_dbg(dev, "  MCTRL.... : (0x%p)=0x%X\n",
                priv->smba + ISMT_MSTR_MCTRL,
                readl(priv->smba + ISMT_MSTR_MCTRL));
        dev_dbg(dev, "  MSTS..... : (0x%p)=0x%X\n",
                priv->smba + ISMT_MSTR_MSTS,
                readl(priv->smba + ISMT_MSTR_MSTS));
        dev_dbg(dev, "  MDS...... : (0x%p)=0x%X\n",
                priv->smba + ISMT_MSTR_MDS,
                readl(priv->smba + ISMT_MSTR_MDS));
        dev_dbg(dev, "  RPOLICY.. : (0x%p)=0x%X\n",
                priv->smba + ISMT_MSTR_RPOLICY,
                readl(priv->smba + ISMT_MSTR_RPOLICY));
        dev_dbg(dev, "  SPGT..... : (0x%p)=0x%X\n",
                priv->smba + ISMT_SPGT,
                readl(priv->smba + ISMT_SPGT));
}

/**
 * ismt_submit_desc() - add a descriptor to the ring
 * @priv: iSMT private data
 */
static void ismt_submit_desc(struct ismt_priv *priv)
{
        uint fmhp;
        uint val;

        ismt_desc_dump(priv);
        ismt_gen_reg_dump(priv);
        ismt_mstr_reg_dump(priv);

        /* Set the FMHP (Firmware Master Head Pointer)*/
        fmhp = ((priv->head + 1) % ISMT_DESC_ENTRIES) << 16;
        val = readl(priv->smba + ISMT_MSTR_MCTRL);
        writel((val & ~ISMT_MCTRL_FMHP) | fmhp,
               priv->smba + ISMT_MSTR_MCTRL);

        /* Set the start bit */
        val = readl(priv->smba + ISMT_MSTR_MCTRL);
        writel(val | ISMT_MCTRL_SS,
               priv->smba + ISMT_MSTR_MCTRL);
}

/**
 * ismt_process_desc() - handle the completion of the descriptor
 * @desc: the iSMT hardware descriptor
 * @data: data buffer from the upper layer
 * @priv: ismt_priv struct holding our dma buffer
 * @size: SMBus transaction type
 * @read_write: flag to indicate if this is a read or write
 */
static int ismt_process_desc(const struct ismt_desc *desc,
                             union i2c_smbus_data *data,
                             struct ismt_priv *priv, int size,
                             char read_write)
{
        u8 *dma_buffer = priv->dma_buffer;

        dev_dbg(&priv->pci_dev->dev, "Processing completed descriptor\n");
        __ismt_desc_dump(&priv->pci_dev->dev, desc);

        if (desc->status & ISMT_DESC_SCS) {
                if (read_write == I2C_SMBUS_WRITE &&
                    size != I2C_SMBUS_PROC_CALL)
                        return 0;

                switch (size) {
                case I2C_SMBUS_BYTE:
                case I2C_SMBUS_BYTE_DATA:
                        data->byte = dma_buffer[0];
                        break;
                case I2C_SMBUS_WORD_DATA:
                case I2C_SMBUS_PROC_CALL:
                        data->word = dma_buffer[0] | (dma_buffer[1] << 8);
                        break;
                case I2C_SMBUS_BLOCK_DATA:
                        memcpy(&data->block[1], dma_buffer, desc->rxbytes);
                        data->block[0] = desc->rxbytes;
                        break;
                }
                return 0;
        }

        if (likely(desc->status & ISMT_DESC_NAK))
                return -ENXIO;

        if (desc->status & ISMT_DESC_CRC)
                return -EBADMSG;

        if (desc->status & ISMT_DESC_COL)
                return -EAGAIN;

        if (desc->status & ISMT_DESC_LPR)
                return -EPROTO;

        if (desc->status & (ISMT_DESC_DLTO | ISMT_DESC_CLTO))
                return -ETIMEDOUT;

        return -EIO;
}

/**
 * ismt_access() - process an SMBus command
 * @adap: the i2c host adapter
 * @addr: address of the i2c/SMBus target
 * @flags: command options
 * @read_write: read from or write to device
 * @command: the i2c/SMBus command to issue
 * @size: SMBus transaction type
 * @data: read/write data buffer
 */
static int ismt_access(struct i2c_adapter *adap, u16 addr,
                       unsigned short flags, char read_write, u8 command,
                       int size, union i2c_smbus_data *data)
{
        int ret;
        dma_addr_t dma_addr = 0; /* address of the data buffer */
        u8 dma_size = 0;
        enum dma_data_direction dma_direction = 0;
        struct ismt_desc *desc;
        struct ismt_priv *priv = i2c_get_adapdata(adap);
        struct device *dev = &priv->pci_dev->dev;

        desc = &priv->hw[priv->head];

        /* Initialize the DMA buffer */
        memset(priv->dma_buffer, 0, sizeof(priv->dma_buffer));

        /* Initialize the descriptor */
        memset(desc, 0, sizeof(struct ismt_desc));
        desc->tgtaddr_rw = ISMT_DESC_ADDR_RW(addr, read_write);

        /* Initialize common control bits */
        if (likely(priv->using_msi))
                desc->control = ISMT_DESC_INT | ISMT_DESC_FAIR;
        else
                desc->control = ISMT_DESC_FAIR;

        if ((flags & I2C_CLIENT_PEC) && (size != I2C_SMBUS_QUICK)
            && (size != I2C_SMBUS_I2C_BLOCK_DATA))
                desc->control |= ISMT_DESC_PEC;

        switch (size) {
        case I2C_SMBUS_QUICK:
                dev_dbg(dev, "I2C_SMBUS_QUICK\n");
                break;

        case I2C_SMBUS_BYTE:
                if (read_write == I2C_SMBUS_WRITE) {
                        /*
                         * Send Byte
                         * The command field contains the write data
                         */
                        dev_dbg(dev, "I2C_SMBUS_BYTE:  WRITE\n");
                        desc->control |= ISMT_DESC_CWRL;
                        desc->wr_len_cmd = command;
                } else {
                        /* Receive Byte */
                        dev_dbg(dev, "I2C_SMBUS_BYTE:  READ\n");
                        dma_size = 1;
                        dma_direction = DMA_FROM_DEVICE;
                        desc->rd_len = 1;
                }
                break;

        case I2C_SMBUS_BYTE_DATA:
                if (read_write == I2C_SMBUS_WRITE) {
                        /*
                         * Write Byte
                         * Command plus 1 data byte
                         */
                        dev_dbg(dev, "I2C_SMBUS_BYTE_DATA:  WRITE\n");
                        desc->wr_len_cmd = 2;
                        dma_size = 2;
                        dma_direction = DMA_TO_DEVICE;
                        priv->dma_buffer[0] = command;
                        priv->dma_buffer[1] = data->byte;
                } else {
                        /* Read Byte */
                        dev_dbg(dev, "I2C_SMBUS_BYTE_DATA:  READ\n");
                        desc->control |= ISMT_DESC_CWRL;
                        desc->wr_len_cmd = command;
                        desc->rd_len = 1;
                        dma_size = 1;
                        dma_direction = DMA_FROM_DEVICE;
                }
                break;

        case I2C_SMBUS_WORD_DATA:
                if (read_write == I2C_SMBUS_WRITE) {
                        /* Write Word */
                        dev_dbg(dev, "I2C_SMBUS_WORD_DATA:  WRITE\n");
                        desc->wr_len_cmd = 3;
                        dma_size = 3;
                        dma_direction = DMA_TO_DEVICE;
                        priv->dma_buffer[0] = command;
                        priv->dma_buffer[1] = data->word & 0xff;
                        priv->dma_buffer[2] = data->word >> 8;
                } else {
                        /* Read Word */
                        dev_dbg(dev, "I2C_SMBUS_WORD_DATA:  READ\n");
                        desc->wr_len_cmd = command;
                        desc->control |= ISMT_DESC_CWRL;
                        desc->rd_len = 2;
                        dma_size = 2;
                        dma_direction = DMA_FROM_DEVICE;
                }
                break;

        case I2C_SMBUS_PROC_CALL:
                dev_dbg(dev, "I2C_SMBUS_PROC_CALL\n");
                desc->wr_len_cmd = 3;
                desc->rd_len = 2;
                dma_size = 3;
                dma_direction = DMA_BIDIRECTIONAL;
                priv->dma_buffer[0] = command;
                priv->dma_buffer[1] = data->word & 0xff;
                priv->dma_buffer[2] = data->word >> 8;
                break;

        case I2C_SMBUS_BLOCK_DATA:
                if (read_write == I2C_SMBUS_WRITE) {
                        /* Block Write */
                        dev_dbg(dev, "I2C_SMBUS_BLOCK_DATA:  WRITE\n");
                        dma_size = data->block[0] + 1;
                        dma_direction = DMA_TO_DEVICE;
                        desc->wr_len_cmd = dma_size;
                        desc->control |= ISMT_DESC_BLK;
                        priv->dma_buffer[0] = command;
                        memcpy(&priv->dma_buffer[1], &data->block[1], dma_size);
                } else {
                        /* Block Read */
                        dev_dbg(dev, "I2C_SMBUS_BLOCK_DATA:  READ\n");
                        dma_size = I2C_SMBUS_BLOCK_MAX;
                        dma_direction = DMA_FROM_DEVICE;
                        desc->rd_len = dma_size;
                        desc->wr_len_cmd = command;
                        desc->control |= (ISMT_DESC_BLK | ISMT_DESC_CWRL);
                }
                break;

        default:
                dev_err(dev, "Unsupported transaction %d\n",
                        size);
                return -EOPNOTSUPP;
        }

        /* map the data buffer */
        if (dma_size != 0) {
                dev_dbg(dev, " dev=%p\n", dev);
                dev_dbg(dev, " data=%p\n", data);
                dev_dbg(dev, " dma_buffer=%p\n", priv->dma_buffer);
                dev_dbg(dev, " dma_size=%d\n", dma_size);
                dev_dbg(dev, " dma_direction=%d\n", dma_direction);

                dma_addr = dma_map_single(dev,
                                      priv->dma_buffer,
                                      dma_size,
                                      dma_direction);

                if (dma_mapping_error(dev, dma_addr)) {
                        dev_err(dev, "Error in mapping dma buffer %p\n",
                                priv->dma_buffer);
                        return -EIO;
                }

                dev_dbg(dev, " dma_addr = 0x%016llX\n",
                        (unsigned long long)dma_addr);

                desc->dptr_low = lower_32_bits(dma_addr);
                desc->dptr_high = upper_32_bits(dma_addr);
        }

        INIT_COMPLETION(priv->cmp);

        /* Add the descriptor */
        ismt_submit_desc(priv);

        /* Now we wait for interrupt completion, 1s */
        ret = wait_for_completion_timeout(&priv->cmp, HZ*1);

        /* unmap the data buffer */
        if (dma_size != 0)
                dma_unmap_single(&adap->dev, dma_addr, dma_size, dma_direction);

        if (unlikely(!ret)) {
                dev_err(dev, "completion wait timed out\n");
                ret = -ETIMEDOUT;
                goto out;
        }

        /* do any post processing of the descriptor here */
        ret = ismt_process_desc(desc, data, priv, size, read_write);

out:
        /* Update the ring pointer */
        priv->head++;
        priv->head %= ISMT_DESC_ENTRIES;

        return ret;
}

/**
 * ismt_func() - report which i2c commands are supported by this adapter
 * @adap: the i2c host adapter
 */
static u32 ismt_func(struct i2c_adapter *adap)
{
        return I2C_FUNC_SMBUS_QUICK             |
               I2C_FUNC_SMBUS_BYTE              |
               I2C_FUNC_SMBUS_BYTE_DATA         |
               I2C_FUNC_SMBUS_WORD_DATA         |
               I2C_FUNC_SMBUS_PROC_CALL         |
               I2C_FUNC_SMBUS_BLOCK_DATA        |
               I2C_FUNC_SMBUS_PEC;
}

/**
 * smbus_algorithm - the adapter algorithm and supported functionality
 * @smbus_xfer: the adapter algorithm
 * @functionality: functionality supported by the adapter
 */
static const struct i2c_algorithm smbus_algorithm = {
        .smbus_xfer     = ismt_access,
        .functionality  = ismt_func,
};

/**
 * ismt_handle_isr() - interrupt handler bottom half
 * @priv: iSMT private data
 */
static irqreturn_t ismt_handle_isr(struct ismt_priv *priv)
{
        complete(&priv->cmp);

        return IRQ_HANDLED;
}


/**
 * ismt_do_interrupt() - IRQ interrupt handler
 * @vec: interrupt vector
 * @data: iSMT private data
 */
static irqreturn_t ismt_do_interrupt(int vec, void *data)
{
        u32 val;
        struct ismt_priv *priv = data;

        /*
         * check to see it's our interrupt, return IRQ_NONE if not ours
         * since we are sharing interrupt
         */
        val = readl(priv->smba + ISMT_MSTR_MSTS);

        if (!(val & (ISMT_MSTS_MIS | ISMT_MSTS_MEIS)))
                return IRQ_NONE;
        else
                writel(val | ISMT_MSTS_MIS | ISMT_MSTS_MEIS,
                       priv->smba + ISMT_MSTR_MSTS);

        return ismt_handle_isr(priv);
}

/**
 * ismt_do_msi_interrupt() - MSI interrupt handler
 * @vec: interrupt vector
 * @data: iSMT private data
 */
static irqreturn_t ismt_do_msi_interrupt(int vec, void *data)
{
        return ismt_handle_isr(data);
}

/**
 * ismt_hw_init() - initialize the iSMT hardware
 * @priv: iSMT private data
 */
static void ismt_hw_init(struct ismt_priv *priv)
{
        u32 val;
        struct device *dev = &priv->pci_dev->dev;

        /* initialize the Master Descriptor Base Address (MDBA) */
        writeq(priv->io_rng_dma, priv->smba + ISMT_MSTR_MDBA);

        /* initialize the Master Control Register (MCTRL) */
        writel(ISMT_MCTRL_MEIE, priv->smba + ISMT_MSTR_MCTRL);

        /* initialize the Master Status Register (MSTS) */
        writel(0, priv->smba + ISMT_MSTR_MSTS);

        /* initialize the Master Descriptor Size (MDS) */
        val = readl(priv->smba + ISMT_MSTR_MDS);
        writel((val & ~ISMT_MDS_MASK) | (ISMT_DESC_ENTRIES - 1),
                priv->smba + ISMT_MSTR_MDS);

        /*
         * Set the SMBus speed (could use this for slow HW debuggers)
         */

        val = readl(priv->smba + ISMT_SPGT);

        switch (bus_speed) {
        case 0:
                break;

        case 80:
                dev_dbg(dev, "Setting SMBus clock to 80 kHz\n");
                writel(((val & ~ISMT_SPGT_SPD_MASK) | ISMT_SPGT_SPD_80K),
                        priv->smba + ISMT_SPGT);
                break;

        case 100:
                dev_dbg(dev, "Setting SMBus clock to 100 kHz\n");
                writel(((val & ~ISMT_SPGT_SPD_MASK) | ISMT_SPGT_SPD_100K),
                        priv->smba + ISMT_SPGT);
                break;

        case 400:
                dev_dbg(dev, "Setting SMBus clock to 400 kHz\n");
                writel(((val & ~ISMT_SPGT_SPD_MASK) | ISMT_SPGT_SPD_400K),
                        priv->smba + ISMT_SPGT);
                break;

        case 1000:
                dev_dbg(dev, "Setting SMBus clock to 1000 kHz\n");
                writel(((val & ~ISMT_SPGT_SPD_MASK) | ISMT_SPGT_SPD_1M),
                        priv->smba + ISMT_SPGT);
                break;

        default:
                dev_warn(dev, "Invalid SMBus clock speed, only 0, 80, 100, 400, and 1000 are valid\n");
                break;
        }

        val = readl(priv->smba + ISMT_SPGT);

        switch (val & ISMT_SPGT_SPD_MASK) {
        case ISMT_SPGT_SPD_80K:
                bus_speed = 80;
                break;
        case ISMT_SPGT_SPD_100K:
                bus_speed = 100;
                break;
        case ISMT_SPGT_SPD_400K:
                bus_speed = 400;
                break;
        case ISMT_SPGT_SPD_1M:
                bus_speed = 1000;
                break;
        }
        dev_dbg(dev, "SMBus clock is running at %d kHz\n", bus_speed);
}

/**
 * ismt_dev_init() - initialize the iSMT data structures
 * @priv: iSMT private data
 */
static int ismt_dev_init(struct ismt_priv *priv)
{
        /* allocate memory for the descriptor */
        priv->hw = dmam_alloc_coherent(&priv->pci_dev->dev,
                                       (ISMT_DESC_ENTRIES
                                               * sizeof(struct ismt_desc)),
                                       &priv->io_rng_dma,
                                       GFP_KERNEL);
        if (!priv->hw)
                return -ENOMEM;

        memset(priv->hw, 0, (ISMT_DESC_ENTRIES * sizeof(struct ismt_desc)));

        priv->head = 0;
        init_completion(&priv->cmp);

        return 0;
}

/**
 * ismt_int_init() - initialize interrupts
 * @priv: iSMT private data
 */
static int ismt_int_init(struct ismt_priv *priv)
{
        int err;

        /* Try using MSI interrupts */
        err = pci_enable_msi(priv->pci_dev);
        if (err) {
                dev_warn(&priv->pci_dev->dev,
                         "Unable to use MSI interrupts, falling back to legacy\n");
                goto intx;
        }

        err = devm_request_irq(&priv->pci_dev->dev,
                               priv->pci_dev->irq,
                               ismt_do_msi_interrupt,
                               0,
                               "ismt-msi",
                               priv);
        if (err) {
                pci_disable_msi(priv->pci_dev);
                goto intx;
        }

        priv->using_msi = true;
        goto done;

        /* Try using legacy interrupts */
intx:
        err = devm_request_irq(&priv->pci_dev->dev,
                               priv->pci_dev->irq,
                               ismt_do_interrupt,
                               IRQF_SHARED,
                               "ismt-intx",
                               priv);
        if (err) {
                dev_err(&priv->pci_dev->dev, "no usable interrupts\n");
                return -ENODEV;
        }

        priv->using_msi = false;

done:
        return 0;
}

static struct pci_driver ismt_driver;

/**
 * ismt_probe() - probe for iSMT devices
 * @pdev: PCI-Express device
 * @id: PCI-Express device ID
 */
static int
ismt_probe(struct pci_dev *pdev, const struct pci_device_id *id)
{
        int err;
        struct ismt_priv *priv;
        unsigned long start, len;

        priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
        if (!priv)
                return -ENOMEM;

        pci_set_drvdata(pdev, priv);
        i2c_set_adapdata(&priv->adapter, priv);
        priv->adapter.owner = THIS_MODULE;

        priv->adapter.class = I2C_CLASS_HWMON;

        priv->adapter.algo = &smbus_algorithm;

        /* set up the sysfs linkage to our parent device */
        priv->adapter.dev.parent = &pdev->dev;

        /* number of retries on lost arbitration */
        priv->adapter.retries = ISMT_MAX_RETRIES;

        priv->pci_dev = pdev;

        err = pcim_enable_device(pdev);
        if (err) {
                dev_err(&pdev->dev, "Failed to enable SMBus PCI device (%d)\n",
                        err);
                return err;
        }

        /* enable bus mastering */
        pci_set_master(pdev);

        /* Determine the address of the SMBus area */
        start = pci_resource_start(pdev, SMBBAR);
        len = pci_resource_len(pdev, SMBBAR);
        if (!start || !len) {
                dev_err(&pdev->dev,
                        "SMBus base address uninitialized, upgrade BIOS\n");
                return -ENODEV;
        }

        snprintf(priv->adapter.name, sizeof(priv->adapter.name),
                 "SMBus iSMT adapter at %lx", start);

        dev_dbg(&priv->pci_dev->dev, " start=0x%lX\n", start);
        dev_dbg(&priv->pci_dev->dev, " len=0x%lX\n", len);

        err = acpi_check_resource_conflict(&pdev->resource[SMBBAR]);
        if (err) {
                dev_err(&pdev->dev, "ACPI resource conflict!\n");
                return err;
        }

        err = pci_request_region(pdev, SMBBAR, ismt_driver.name);
        if (err) {
                dev_err(&pdev->dev,
                        "Failed to request SMBus region 0x%lx-0x%lx\n",
                        start, start + len);
                return err;
        }

        priv->smba = pcim_iomap(pdev, SMBBAR, len);
        if (!priv->smba) {
                dev_err(&pdev->dev, "Unable to ioremap SMBus BAR\n");
                err = -ENODEV;
                goto fail;
        }

        if ((pci_set_dma_mask(pdev, DMA_BIT_MASK(64)) != 0) ||
            (pci_set_consistent_dma_mask(pdev, DMA_BIT_MASK(64)) != 0)) {
                if ((pci_set_dma_mask(pdev, DMA_BIT_MASK(32)) != 0) ||
                    (pci_set_consistent_dma_mask(pdev,
                                                 DMA_BIT_MASK(32)) != 0)) {
                        dev_err(&pdev->dev, "pci_set_dma_mask fail %p\n",
                                pdev);
                        err = -ENODEV;
                        goto fail;
                }
        }

        err = ismt_dev_init(priv);
        if (err)
                goto fail;

        ismt_hw_init(priv);

        err = ismt_int_init(priv);
        if (err)
                goto fail;

        err = i2c_add_adapter(&priv->adapter);
        if (err) {
                dev_err(&pdev->dev, "Failed to add SMBus iSMT adapter\n");
                err = -ENODEV;
                goto fail;
        }
        return 0;

fail:
        pci_release_region(pdev, SMBBAR);
        return err;
}

/**
 * ismt_remove() - release driver resources
 * @pdev: PCI-Express device
 */
static void ismt_remove(struct pci_dev *pdev)
{
        struct ismt_priv *priv = pci_get_drvdata(pdev);

        i2c_del_adapter(&priv->adapter);
        pci_release_region(pdev, SMBBAR);
}

/**
 * ismt_suspend() - place the device in suspend
 * @pdev: PCI-Express device
 * @mesg: PM message
 */
#ifdef CONFIG_PM
static int ismt_suspend(struct pci_dev *pdev, pm_message_t mesg)
{
        pci_save_state(pdev);
        pci_set_power_state(pdev, pci_choose_state(pdev, mesg));
        return 0;
}

/**
 * ismt_resume() - PCI resume code
 * @pdev: PCI-Express device
 */
static int ismt_resume(struct pci_dev *pdev)
{
        pci_set_power_state(pdev, PCI_D0);
        pci_restore_state(pdev);
        return pci_enable_device(pdev);
}

#else

#define ismt_suspend NULL
#define ismt_resume NULL

#endif

static struct pci_driver ismt_driver = {
        .name = "ismt_smbus",
        .id_table = ismt_ids,
        .probe = ismt_probe,
        .remove = ismt_remove,
        .suspend = ismt_suspend,
        .resume = ismt_resume,
};

module_pci_driver(ismt_driver);

MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("Bill E. Brown <bill.e.brown@intel.com>");
MODULE_DESCRIPTION("Intel SMBus Message Transport (iSMT) driver");