/*
 *  rar_register.c - An Intel Restricted Access Region register driver
 *
 *  Copyright(c) 2009 Intel Corporation. All rights reserved.
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License as
 *  published by the Free Software Foundation; either version 2 of the
 *  License, or (at your option) any later version.
 *
 *  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., 59 Temple Place - Suite 330, Boston, MA
 *  02111-1307, USA.
 *
 * -------------------------------------------------------------------
 *  20091204 Mark Allyn <mark.a.allyn@intel.com>
 *           Ossama Othman <ossama.othman@intel.com>
 *      Cleanup per feedback from Alan Cox and Arjan Van De Ven
 *
 *  20090806 Ossama Othman <ossama.othman@intel.com>
 *      Return zero high address if upper 22 bits is zero.
 *      Cleaned up checkpatch errors.
 *      Clarified that driver is dealing with bus addresses.
 *
 *  20090702 Ossama Othman <ossama.othman@intel.com>
 *      Removed unnecessary include directives
 *      Cleaned up spinlocks.
 *      Cleaned up logging.
 *      Improved invalid parameter checks.
 *      Fixed and simplified RAR address retrieval and RAR locking
 *      code.
 *
 *  20090626 Mark Allyn <mark.a.allyn@intel.com>
 *      Initial publish
 */

#include <linux/module.h>
#include <linux/pci.h>
#include <linux/spinlock.h>
#include <linux/device.h>
#include <linux/kernel.h>
#include <linux/rar_register.h>

/* === Lincroft Message Bus Interface === */
#define LNC_MCR_OFFSET          0xD0    /* Message Control Register */
#define LNC_MDR_OFFSET          0xD4    /* Message Data Register */

/* Message Opcodes */
#define LNC_MESSAGE_READ_OPCODE 0xD0
#define LNC_MESSAGE_WRITE_OPCODE 0xE0

/* Message Write Byte Enables */
#define LNC_MESSAGE_BYTE_WRITE_ENABLES  0xF

/* B-unit Port */
#define LNC_BUNIT_PORT  0x3

/* === Lincroft B-Unit Registers - Programmed by IA32 firmware === */
#define LNC_BRAR0L      0x10
#define LNC_BRAR0H      0x11
#define LNC_BRAR1L      0x12
#define LNC_BRAR1H      0x13
/* Reserved for SeP */
#define LNC_BRAR2L      0x14
#define LNC_BRAR2H      0x15

/* Moorestown supports three restricted access regions. */
#define MRST_NUM_RAR 3

/* RAR Bus Address Range */
struct rar_addr {
        dma_addr_t low;
        dma_addr_t high;
};

/*
 *      We create one of these for each RAR
 */
struct client {
        int (*callback)(unsigned long data);
        unsigned long driver_priv;
        bool busy;
};

static DEFINE_MUTEX(rar_mutex);
static DEFINE_MUTEX(lnc_reg_mutex);

/*
 *      One per RAR device (currently only one device)
 */
struct rar_device {
        struct rar_addr rar_addr[MRST_NUM_RAR];
        struct pci_dev *rar_dev;
        bool registered;
        bool allocated;
        struct client client[MRST_NUM_RAR];
};

/* Current platforms have only one rar_device for 3 rar regions */
static struct rar_device my_rar_device;

/*
 *      Abstract out multiple device support. Current platforms only
 *      have a single RAR device.
 */

/**
 *      alloc_rar_device        -       return a new RAR structure
 *
 *      Return a new (but not yet ready) RAR device object
 */
static struct rar_device *alloc_rar_device(void)
{
        if (my_rar_device.allocated)
                return NULL;
        my_rar_device.allocated = 1;
        return &my_rar_device;
}

/**
 *      free_rar_device         -       free a RAR object
 *      @rar: the RAR device being freed
 *
 *      Release a RAR object and any attached resources
 */
static void free_rar_device(struct rar_device *rar)
{
        pci_dev_put(rar->rar_dev);
        rar->allocated = 0;
}

/**
 *      _rar_to_device          -       return the device handling this RAR
 *      @rar: RAR number
 *      @off: returned offset
 *
 *      Internal helper for looking up RAR devices. This and alloc are the
 *      two functions that need touching to go to multiple RAR devices.
 */
static struct rar_device *_rar_to_device(int rar, int *off)
{
        if (rar >= 0 && rar < MRST_NUM_RAR) {
                *off = rar;
                return &my_rar_device;
        }
        return NULL;
}

/**
 *      rar_to_device           -       return the device handling this RAR
 *      @rar: RAR number
 *      @off: returned offset
 *
 *      Return the device this RAR maps to if one is present, otherwise
 *      returns NULL. Reports the offset relative to the base of this
 *      RAR device in off.
 */
static struct rar_device *rar_to_device(int rar, int *off)
{
        struct rar_device *rar_dev = _rar_to_device(rar, off);
        if (rar_dev == NULL || !rar_dev->registered)
                return NULL;
        return rar_dev;
}

/**
 *      rar_to_client           -       return the client handling this RAR
 *      @rar: RAR number
 *
 *      Return the client this RAR maps to if a mapping is known, otherwise
 *      returns NULL.
 */
static struct client *rar_to_client(int rar)
{
        int idx;
        struct rar_device *r = _rar_to_device(rar, &idx);
        if (r != NULL)
                return &r->client[idx];
        return NULL;
}

/**
 *      rar_read_addr           -       retrieve a RAR mapping
 *      @pdev: PCI device for the RAR
 *      @offset: offset for message
 *      @addr: returned address
 *
 *      Reads the address of a given RAR register. Returns 0 on success
 *      or an error code on failure.
 */
static int rar_read_addr(struct pci_dev *pdev, int offset, dma_addr_t *addr)
{
        /*
         * ======== The Lincroft Message Bus Interface ========
         * Lincroft registers may be obtained via PCI from
         * the host bridge using the Lincroft Message Bus
         * Interface.  That message bus interface is generally
         * comprised of two registers: a control register (MCR, 0xDO)
         * and a data register (MDR, 0xD4).
         *
         * The MCR (message control register) format is the following:
         *   1.  [31:24]: Opcode
         *   2.  [23:16]: Port
         *   3.  [15:8]: Register Offset
         *   4.  [7:4]: Byte Enables (use 0xF to set all of these bits
         *              to 1)
         *   5.  [3:0]: reserved
         *
         *  Read (0xD0) and write (0xE0) opcodes are written to the
         *  control register when reading and writing to Lincroft
         *  registers, respectively.
         *
         *  We're interested in registers found in the Lincroft
         *  B-unit.  The B-unit port is 0x3.
         *
         *  The six B-unit RAR register offsets we use are listed
         *  earlier in this file.
         *
         *  Lastly writing to the MCR register requires the "Byte
         *  enables" bits to be set to 1.  This may be achieved by
         *  writing 0xF at bit 4.
         *
         * The MDR (message data register) format is the following:
         *   1. [31:0]: Read/Write Data
         *
         *  Data being read from this register is only available after
         *  writing the appropriate control message to the MCR
         *  register.
         *
         *  Data being written to this register must be written before
         *  writing the appropriate control message to the MCR
         *  register.
        */

        int result;
        u32 addr32;

        /* Construct control message */
        u32 const message =
                 (LNC_MESSAGE_READ_OPCODE << 24)
                 | (LNC_BUNIT_PORT << 16)
                 | (offset << 8)
                 | (LNC_MESSAGE_BYTE_WRITE_ENABLES << 4);

        dev_dbg(&pdev->dev, "Offset for 'get' LNC MSG is %x\n", offset);

        /*
        * We synchronize access to the Lincroft MCR and MDR registers
        * until BOTH the command is issued through the MCR register
        * and the corresponding data is read from the MDR register.
        * Otherwise a race condition would exist between accesses to
        * both registers.
        */

        mutex_lock(&lnc_reg_mutex);

        /* Send the control message */
        result = pci_write_config_dword(pdev, LNC_MCR_OFFSET, message);
        if (!result) {
                /* Read back the address as a 32bit value */
                result = pci_read_config_dword(pdev, LNC_MDR_OFFSET, &addr32);
                *addr = (dma_addr_t)addr32;
        }
        mutex_unlock(&lnc_reg_mutex);
        return result;
}

/**
 *      rar_set_addr            -       Set a RAR mapping
 *      @pdev: PCI device for the RAR
 *      @offset: offset for message
 *      @addr: address to set
 *
 *      Sets the address of a given RAR register. Returns 0 on success
 *      or an error code on failure.
 */
static int rar_set_addr(struct pci_dev *pdev,
        int offset,
        dma_addr_t addr)
{
        /*
        * Data being written to this register must be written before
        * writing the appropriate control message to the MCR
        * register.
        * See rar_get_addrs() for a description of the
        * message bus interface being used here.
        */

        int result;

        /* Construct control message */
        u32 const message = (LNC_MESSAGE_WRITE_OPCODE << 24)
                | (LNC_BUNIT_PORT << 16)
                | (offset << 8)
                | (LNC_MESSAGE_BYTE_WRITE_ENABLES << 4);

        /*
        * We synchronize access to the Lincroft MCR and MDR registers
        * until BOTH the command is issued through the MCR register
        * and the corresponding data is read from the MDR register.
        * Otherwise a race condition would exist between accesses to
        * both registers.
        */

        mutex_lock(&lnc_reg_mutex);

        /* Send the control message */
        result = pci_write_config_dword(pdev, LNC_MDR_OFFSET, addr);
        if (!result)
                /* And address */
                result = pci_write_config_dword(pdev, LNC_MCR_OFFSET, message);

        mutex_unlock(&lnc_reg_mutex);
        return result;
}

/*
 *      rar_init_params         -       Initialize RAR parameters
 *      @rar: RAR device to initialise
 *
 *      Initialize RAR parameters, such as bus addresses, etc. Returns 0
 *      on success, or an error code on failure.
 */
static int init_rar_params(struct rar_device *rar)
{
        struct pci_dev *pdev = rar->rar_dev;
        unsigned int i;
        int result = 0;
        int offset = 0x10;      /* RAR 0 to 2 in order low/high/low/high/... */

        /* Retrieve RAR start and end bus addresses.
        * Access the RAR registers through the Lincroft Message Bus
        * Interface on PCI device: 00:00.0 Host bridge.
        */

        for (i = 0; i < MRST_NUM_RAR; ++i) {
                struct rar_addr *addr = &rar->rar_addr[i];

                result = rar_read_addr(pdev, offset++, &addr->low);
                if (result != 0)
                        return result;

                result = rar_read_addr(pdev, offset++, &addr->high);
                if (result != 0)
                        return result;


                /*
                * Only the upper 22 bits of the RAR addresses are
                * stored in their corresponding RAR registers so we
                * must set the lower 10 bits accordingly.

                * The low address has its lower 10 bits cleared, and
                * the high address has all its lower 10 bits set,
                * e.g.:
                * low = 0x2ffffc00
                */

                addr->low &= (dma_addr_t)0xfffffc00u;

                /*
                * Set bits 9:0 on uppser address if bits 31:10 are non
                * zero; otherwize clear all bits
                */

                if ((addr->high & 0xfffffc00u) == 0)
                        addr->high = 0;
                else
                        addr->high |= 0x3ffu;
        }
        /* Done accessing the device. */

        if (result == 0) {
                for (i = 0; i != MRST_NUM_RAR; ++i) {
                        /*
                        * "BRAR" refers to the RAR registers in the
                        * Lincroft B-unit.
                        */
                        dev_info(&pdev->dev, "BRAR[%u] bus address range = "
                          "[%lx, %lx]\n", i,
                          (unsigned long)rar->rar_addr[i].low,
                          (unsigned long)rar->rar_addr[i].high);
                }
        }
        return result;
}

/**
 *      rar_get_address         -       get the bus address in a RAR
 *      @start: return value of start address of block
 *      @end: return value of end address of block
 *
 *      The rar_get_address function is used by other device drivers
 *      to obtain RAR address information on a RAR. It takes three
 *      parameters:
 *
 *      The function returns a 0 upon success or an error if there is no RAR
 *      facility on this system.
 */
int rar_get_address(int rar_index, dma_addr_t *start, dma_addr_t *end)
{
        int idx;
        struct rar_device *rar = rar_to_device(rar_index, &idx);

        if (rar == NULL) {
                WARN_ON(1);
                return -ENODEV;
        }

        *start = rar->rar_addr[idx].low;
        *end = rar->rar_addr[idx].high;
        return 0;
}
EXPORT_SYMBOL(rar_get_address);

/**
 *      rar_lock        -       lock a RAR register
 *      @rar_index: RAR to lock (0-2)
 *
 *      The rar_lock function is ued by other device drivers to lock an RAR.
 *      once a RAR is locked, it stays locked until the next system reboot.
 *
 *      The function returns a 0 upon success or an error if there is no RAR
 *      facility on this system, or the locking fails
 */
int rar_lock(int rar_index)
{
        struct rar_device *rar;
        int result;
        int idx;
        dma_addr_t low, high;

        rar = rar_to_device(rar_index, &idx);

        if (rar == NULL) {
                WARN_ON(1);
                return -EINVAL;
        }

        low = rar->rar_addr[idx].low & 0xfffffc00u;
        high = rar->rar_addr[idx].high & 0xfffffc00u;

        /*
        * Only allow I/O from the graphics and Langwell;
        * not from the x86 processor
        */

        if (rar_index == RAR_TYPE_VIDEO) {
                low |= 0x00000009;
                high |= 0x00000015;
        } else if (rar_index == RAR_TYPE_AUDIO) {
                /* Only allow I/O from Langwell; nothing from x86 */
                low |= 0x00000008;
                high |= 0x00000018;
        } else
                /* Read-only from all agents */
                high |= 0x00000018;

        /*
        * Now program the register using the Lincroft message
        * bus interface.
        */
        result = rar_set_addr(rar->rar_dev,
                                2 * idx, low);

        if (result == 0)
                result = rar_set_addr(rar->rar_dev,
                                2 * idx + 1, high);

        return result;
}
EXPORT_SYMBOL(rar_lock);

/**
 *      register_rar            -       register a RAR handler
 *      @num: RAR we wish to register for
 *      @callback: function to call when RAR support is available
 *      @data: data to pass to this function
 *
 *      The register_rar function is to used by other device drivers
 *      to ensure that this driver is ready. As we cannot be sure of
 *      the compile/execute order of drivers in the kernel, it is
 *      best to give this driver a callback function to call when
 *      it is ready to give out addresses. The callback function
 *      would have those steps that continue the initialization of
 *      a driver that do require a valid RAR address. One of those
 *      steps would be to call rar_get_address()
 *
 *      This function return 0 on success or an error code on failure.
 */
int register_rar(int num, int (*callback)(unsigned long data),
                                                        unsigned long data)
{
        /* For now we hardcode a single RAR device */
        struct rar_device *rar;
        struct client *c;
        int idx;
        int retval = 0;

        mutex_lock(&rar_mutex);

        /* Do we have a client mapping for this RAR number ? */
        c = rar_to_client(num);
        if (c == NULL) {
                retval = -ERANGE;
                goto done;
        }
        /* Is it claimed ? */
        if (c->busy) {
                retval = -EBUSY;
                goto done;
        }
        c->busy = 1;

        /* See if we have a handler for this RAR yet, if we do then fire it */
        rar = rar_to_device(num, &idx);

        if (rar) {
                /*
                * if the driver already registered, then we can simply
                * call the callback right now
                */
                (*callback)(data);
                goto done;
        }

        /* Arrange to be called back when the hardware is found */
        c->callback = callback;
        c->driver_priv = data;
done:
        mutex_unlock(&rar_mutex);
        return retval;
}
EXPORT_SYMBOL(register_rar);

/**
 *      unregister_rar  -       release a RAR allocation
 *      @num: RAR number
 *
 *      Releases a RAR allocation, or pending allocation. If a callback is
 *      pending then this function will either complete before the unregister
 *      returns or not at all.
 */

void unregister_rar(int num)
{
        struct client *c;

        mutex_lock(&rar_mutex);
        c = rar_to_client(num);
        if (c == NULL || !c->busy)
                WARN_ON(1);
        else
                c->busy = 0;
        mutex_unlock(&rar_mutex);
}
EXPORT_SYMBOL(unregister_rar);

/**
 *      rar_callback            -       Process callbacks
 *      @rar: new RAR device
 *
 *      Process the callbacks for a newly found RAR device.
 */

static void rar_callback(struct rar_device *rar)
{
        struct client *c = &rar->client[0];
        int i;

        mutex_lock(&rar_mutex);

        rar->registered = 1;    /* Ensure no more callbacks queue */

        for (i = 0; i < MRST_NUM_RAR; i++) {
                if (c->callback && c->busy) {
                        c->callback(c->driver_priv);
                        c->callback = NULL;
                }
                c++;
        }
        mutex_unlock(&rar_mutex);
}

/**
 *      rar_probe               -       PCI probe callback
 *      @dev: PCI device
 *      @id: matching entry in the match table
 *
 *      A RAR device has been discovered. Initialise it and if successful
 *      process any pending callbacks that can now be completed.
 */
static int rar_probe(struct pci_dev *dev, const struct pci_device_id *id)
{
        int error;
        struct rar_device *rar;

        dev_dbg(&dev->dev, "PCI probe starting\n");

        rar = alloc_rar_device();
        if (rar == NULL)
                return -EBUSY;

        /* Enable the device */
        error = pci_enable_device(dev);
        if (error) {
                dev_err(&dev->dev,
                        "Error enabling RAR register PCI device\n");
                goto end_function;
        }

        /* Fill in the rar_device structure */
        rar->rar_dev = pci_dev_get(dev);
        pci_set_drvdata(dev, rar);

        /*
         * Initialize the RAR parameters, which have to be retrieved
         * via the message bus interface.
         */
        error = init_rar_params(rar);
        if (error) {
                pci_disable_device(dev);
                dev_err(&dev->dev, "Error retrieving RAR addresses\n");
                goto end_function;
        }
        /* now call anyone who has registered (using callbacks) */
        rar_callback(rar);
        return 0;
end_function:
        free_rar_device(rar);
        return error;
}

static DEFINE_PCI_DEVICE_TABLE(rar_pci_id_tbl) = {
        { PCI_VDEVICE(INTEL, 0x4110) },
        { 0 }
};

MODULE_DEVICE_TABLE(pci, rar_pci_id_tbl);

/* field for registering driver to PCI device */
static struct pci_driver rar_pci_driver = {
        .name = "rar_register_driver",
        .id_table = rar_pci_id_tbl,
        .probe = rar_probe,
        /* Cannot be unplugged - no remove */
};

static int __init rar_init_handler(void)
{
        return pci_register_driver(&rar_pci_driver);
}

static void __exit rar_exit_handler(void)
{
        pci_unregister_driver(&rar_pci_driver);
}

module_init(rar_init_handler);
module_exit(rar_exit_handler);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Intel Restricted Access Region Register Driver");