/*
 * FSI core driver
 *
 * Copyright (C) IBM Corporation 2016
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 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.
 */

#include <linux/crc4.h>
#include <linux/device.h>
#include <linux/fsi.h>
#include <linux/idr.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/slab.h>
#include <linux/bitops.h>

#include "fsi-master.h"

#define CREATE_TRACE_POINTS
#include <trace/events/fsi.h>

#define FSI_SLAVE_CONF_NEXT_MASK        GENMASK(31, 31)
#define FSI_SLAVE_CONF_SLOTS_MASK       GENMASK(23, 16)
#define FSI_SLAVE_CONF_SLOTS_SHIFT      16
#define FSI_SLAVE_CONF_VERSION_MASK     GENMASK(15, 12)
#define FSI_SLAVE_CONF_VERSION_SHIFT    12
#define FSI_SLAVE_CONF_TYPE_MASK        GENMASK(11, 4)
#define FSI_SLAVE_CONF_TYPE_SHIFT       4
#define FSI_SLAVE_CONF_CRC_SHIFT        4
#define FSI_SLAVE_CONF_CRC_MASK         GENMASK(3, 0)
#define FSI_SLAVE_CONF_DATA_BITS        28

#define FSI_PEEK_BASE                   0x410

static const int engine_page_size = 0x400;

#define FSI_SLAVE_BASE                  0x800

/*
 * FSI slave engine control register offsets
 */
#define FSI_SMODE               0x0     /* R/W: Mode register */
#define FSI_SISC                0x8     /* R/W: Interrupt condition */
#define FSI_SSTAT               0x14    /* R  : Slave status */
#define FSI_LLMODE              0x100   /* R/W: Link layer mode register */

/*
 * SMODE fields
 */
#define FSI_SMODE_WSC           0x80000000      /* Warm start done */
#define FSI_SMODE_ECRC          0x20000000      /* Hw CRC check */
#define FSI_SMODE_SID_SHIFT     24              /* ID shift */
#define FSI_SMODE_SID_MASK      3               /* ID Mask */
#define FSI_SMODE_ED_SHIFT      20              /* Echo delay shift */
#define FSI_SMODE_ED_MASK       0xf             /* Echo delay mask */
#define FSI_SMODE_SD_SHIFT      16              /* Send delay shift */
#define FSI_SMODE_SD_MASK       0xf             /* Send delay mask */
#define FSI_SMODE_LBCRR_SHIFT   8               /* Clk ratio shift */
#define FSI_SMODE_LBCRR_MASK    0xf             /* Clk ratio mask */

/*
 * LLMODE fields
 */
#define FSI_LLMODE_ASYNC        0x1

#define FSI_SLAVE_SIZE_23b              0x800000

static DEFINE_IDA(master_ida);

struct fsi_slave {
        struct device           dev;
        struct fsi_master       *master;
        int                     id;
        int                     link;
        uint32_t                size;   /* size of slave address space */
};

#define to_fsi_master(d) container_of(d, struct fsi_master, dev)
#define to_fsi_slave(d) container_of(d, struct fsi_slave, dev)

static const int slave_retries = 2;
static int discard_errors;

static int fsi_master_read(struct fsi_master *master, int link,
                uint8_t slave_id, uint32_t addr, void *val, size_t size);
static int fsi_master_write(struct fsi_master *master, int link,
                uint8_t slave_id, uint32_t addr, const void *val, size_t size);
static int fsi_master_break(struct fsi_master *master, int link);

/*
 * fsi_device_read() / fsi_device_write() / fsi_device_peek()
 *
 * FSI endpoint-device support
 *
 * Read / write / peek accessors for a client
 *
 * Parameters:
 * dev:  Structure passed to FSI client device drivers on probe().
 * addr: FSI address of given device.  Client should pass in its base address
 *       plus desired offset to access its register space.
 * val:  For read/peek this is the value read at the specified address. For
 *       write this is value to write to the specified address.
 *       The data in val must be FSI bus endian (big endian).
 * size: Size in bytes of the operation.  Sizes supported are 1, 2 and 4 bytes.
 *       Addresses must be aligned on size boundaries or an error will result.
 */
int fsi_device_read(struct fsi_device *dev, uint32_t addr, void *val,
                size_t size)
{
        if (addr > dev->size || size > dev->size || addr > dev->size - size)
                return -EINVAL;

        return fsi_slave_read(dev->slave, dev->addr + addr, val, size);
}
EXPORT_SYMBOL_GPL(fsi_device_read);

int fsi_device_write(struct fsi_device *dev, uint32_t addr, const void *val,
                size_t size)
{
        if (addr > dev->size || size > dev->size || addr > dev->size - size)
                return -EINVAL;

        return fsi_slave_write(dev->slave, dev->addr + addr, val, size);
}
EXPORT_SYMBOL_GPL(fsi_device_write);

int fsi_device_peek(struct fsi_device *dev, void *val)
{
        uint32_t addr = FSI_PEEK_BASE + ((dev->unit - 2) * sizeof(uint32_t));

        return fsi_slave_read(dev->slave, addr, val, sizeof(uint32_t));
}

static void fsi_device_release(struct device *_device)
{
        struct fsi_device *device = to_fsi_dev(_device);

        of_node_put(device->dev.of_node);
        kfree(device);
}

static struct fsi_device *fsi_create_device(struct fsi_slave *slave)
{
        struct fsi_device *dev;

        dev = kzalloc(sizeof(*dev), GFP_KERNEL);
        if (!dev)
                return NULL;

        dev->dev.parent = &slave->dev;
        dev->dev.bus = &fsi_bus_type;
        dev->dev.release = fsi_device_release;

        return dev;
}

/* FSI slave support */
static int fsi_slave_calc_addr(struct fsi_slave *slave, uint32_t *addrp,
                uint8_t *idp)
{
        uint32_t addr = *addrp;
        uint8_t id = *idp;

        if (addr > slave->size)
                return -EINVAL;

        /* For 23 bit addressing, we encode the extra two bits in the slave
         * id (and the slave's actual ID needs to be 0).
         */
        if (addr > 0x1fffff) {
                if (slave->id != 0)
                        return -EINVAL;
                id = (addr >> 21) & 0x3;
                addr &= 0x1fffff;
        }

        *addrp = addr;
        *idp = id;
        return 0;
}

static int fsi_slave_report_and_clear_errors(struct fsi_slave *slave)
{
        struct fsi_master *master = slave->master;
        uint32_t irq, stat;
        int rc, link;
        uint8_t id;

        link = slave->link;
        id = slave->id;

        rc = fsi_master_read(master, link, id, FSI_SLAVE_BASE + FSI_SISC,
                        &irq, sizeof(irq));
        if (rc)
                return rc;

        rc =  fsi_master_read(master, link, id, FSI_SLAVE_BASE + FSI_SSTAT,
                        &stat, sizeof(stat));
        if (rc)
                return rc;

        dev_dbg(&slave->dev, "status: 0x%08x, sisc: 0x%08x\n",
                        be32_to_cpu(stat), be32_to_cpu(irq));

        /* clear interrupts */
        return fsi_master_write(master, link, id, FSI_SLAVE_BASE + FSI_SISC,
                        &irq, sizeof(irq));
}

static int fsi_slave_set_smode(struct fsi_master *master, int link, int id);

static int fsi_slave_handle_error(struct fsi_slave *slave, bool write,
                                  uint32_t addr, size_t size)
{
        struct fsi_master *master = slave->master;
        int rc, link;
        uint32_t reg;
        uint8_t id;

        if (discard_errors)
                return -1;

        link = slave->link;
        id = slave->id;

        dev_dbg(&slave->dev, "handling error on %s to 0x%08x[%zd]",
                        write ? "write" : "read", addr, size);

        /* try a simple clear of error conditions, which may fail if we've lost
         * communication with the slave
         */
        rc = fsi_slave_report_and_clear_errors(slave);
        if (!rc)
                return 0;

        /* send a TERM and retry */
        if (master->term) {
                rc = master->term(master, link, id);
                if (!rc) {
                        rc = fsi_master_read(master, link, id, 0,
                                        &reg, sizeof(reg));
                        if (!rc)
                                rc = fsi_slave_report_and_clear_errors(slave);
                        if (!rc)
                                return 0;
                }
        }

        /* getting serious, reset the slave via BREAK */
        rc = fsi_master_break(master, link);
        if (rc)
                return rc;

        rc = fsi_slave_set_smode(master, link, id);
        if (rc)
                return rc;

        return fsi_slave_report_and_clear_errors(slave);
}

int fsi_slave_read(struct fsi_slave *slave, uint32_t addr,
                        void *val, size_t size)
{
        uint8_t id = slave->id;
        int rc, err_rc, i;

        rc = fsi_slave_calc_addr(slave, &addr, &id);
        if (rc)
                return rc;

        for (i = 0; i < slave_retries; i++) {
                rc = fsi_master_read(slave->master, slave->link,
                                id, addr, val, size);
                if (!rc)
                        break;

                err_rc = fsi_slave_handle_error(slave, false, addr, size);
                if (err_rc)
                        break;
        }

        return rc;
}
EXPORT_SYMBOL_GPL(fsi_slave_read);

int fsi_slave_write(struct fsi_slave *slave, uint32_t addr,
                        const void *val, size_t size)
{
        uint8_t id = slave->id;
        int rc, err_rc, i;

        rc = fsi_slave_calc_addr(slave, &addr, &id);
        if (rc)
                return rc;

        for (i = 0; i < slave_retries; i++) {
                rc = fsi_master_write(slave->master, slave->link,
                                id, addr, val, size);
                if (!rc)
                        break;

                err_rc = fsi_slave_handle_error(slave, true, addr, size);
                if (err_rc)
                        break;
        }

        return rc;
}
EXPORT_SYMBOL_GPL(fsi_slave_write);

extern int fsi_slave_claim_range(struct fsi_slave *slave,
                uint32_t addr, uint32_t size)
{
        if (addr + size < addr)
                return -EINVAL;

        if (addr + size > slave->size)
                return -EINVAL;

        /* todo: check for overlapping claims */
        return 0;
}
EXPORT_SYMBOL_GPL(fsi_slave_claim_range);

extern void fsi_slave_release_range(struct fsi_slave *slave,
                uint32_t addr, uint32_t size)
{
}
EXPORT_SYMBOL_GPL(fsi_slave_release_range);

static bool fsi_device_node_matches(struct device *dev, struct device_node *np,
                uint32_t addr, uint32_t size)
{
        unsigned int len, na, ns;
        const __be32 *prop;
        uint32_t psize;

        na = of_n_addr_cells(np);
        ns = of_n_size_cells(np);

        if (na != 1 || ns != 1)
                return false;

        prop = of_get_property(np, "reg", &len);
        if (!prop || len != 8)
                return false;

        if (of_read_number(prop, 1) != addr)
                return false;

        psize = of_read_number(prop + 1, 1);
        if (psize != size) {
                dev_warn(dev,
                        "node %s matches probed address, but not size (got 0x%x, expected 0x%x)",
                        of_node_full_name(np), psize, size);
        }

        return true;
}

/* Find a matching node for the slave engine at @address, using @size bytes
 * of space. Returns NULL if not found, or a matching node with refcount
 * already incremented.
 */
static struct device_node *fsi_device_find_of_node(struct fsi_device *dev)
{
        struct device_node *parent, *np;

        parent = dev_of_node(&dev->slave->dev);
        if (!parent)
                return NULL;

        for_each_child_of_node(parent, np) {
                if (fsi_device_node_matches(&dev->dev, np,
                                        dev->addr, dev->size))
                        return np;
        }

        return NULL;
}

static int fsi_slave_scan(struct fsi_slave *slave)
{
        uint32_t engine_addr;
        uint32_t conf;
        int rc, i;

        /*
         * scan engines
         *
         * We keep the peek mode and slave engines for the core; so start
         * at the third slot in the configuration table. We also need to
         * skip the chip ID entry at the start of the address space.
         */
        engine_addr = engine_page_size * 3;
        for (i = 2; i < engine_page_size / sizeof(uint32_t); i++) {
                uint8_t slots, version, type, crc;
                struct fsi_device *dev;

                rc = fsi_slave_read(slave, (i + 1) * sizeof(conf),
                                &conf, sizeof(conf));
                if (rc) {
                        dev_warn(&slave->dev,
                                "error reading slave registers\n");
                        return -1;
                }
                conf = be32_to_cpu(conf);

                crc = crc4(0, conf, 32);
                if (crc) {
                        dev_warn(&slave->dev,
                                "crc error in slave register at 0x%04x\n",
                                i);
                        return -1;
                }

                slots = (conf & FSI_SLAVE_CONF_SLOTS_MASK)
                        >> FSI_SLAVE_CONF_SLOTS_SHIFT;
                version = (conf & FSI_SLAVE_CONF_VERSION_MASK)
                        >> FSI_SLAVE_CONF_VERSION_SHIFT;
                type = (conf & FSI_SLAVE_CONF_TYPE_MASK)
                        >> FSI_SLAVE_CONF_TYPE_SHIFT;

                /*
                 * Unused address areas are marked by a zero type value; this
                 * skips the defined address areas
                 */
                if (type != 0 && slots != 0) {

                        /* create device */
                        dev = fsi_create_device(slave);
                        if (!dev)
                                return -ENOMEM;

                        dev->slave = slave;
                        dev->engine_type = type;
                        dev->version = version;
                        dev->unit = i;
                        dev->addr = engine_addr;
                        dev->size = slots * engine_page_size;

                        dev_dbg(&slave->dev,
                        "engine[%i]: type %x, version %x, addr %x size %x\n",
                                        dev->unit, dev->engine_type, version,
                                        dev->addr, dev->size);

                        dev_set_name(&dev->dev, "%02x:%02x:%02x:%02x",
                                        slave->master->idx, slave->link,
                                        slave->id, i - 2);
                        dev->dev.of_node = fsi_device_find_of_node(dev);

                        rc = device_register(&dev->dev);
                        if (rc) {
                                dev_warn(&slave->dev, "add failed: %d\n", rc);
                                put_device(&dev->dev);
                        }
                }

                engine_addr += slots * engine_page_size;

                if (!(conf & FSI_SLAVE_CONF_NEXT_MASK))
                        break;
        }

        return 0;
}

static ssize_t fsi_slave_sysfs_raw_read(struct file *file,
                struct kobject *kobj, struct bin_attribute *attr, char *buf,
                loff_t off, size_t count)
{
        struct fsi_slave *slave = to_fsi_slave(kobj_to_dev(kobj));
        size_t total_len, read_len;
        int rc;

        if (off < 0)
                return -EINVAL;

        if (off > 0xffffffff || count > 0xffffffff || off + count > 0xffffffff)
                return -EINVAL;

        for (total_len = 0; total_len < count; total_len += read_len) {
                read_len = min_t(size_t, count, 4);
                read_len -= off & 0x3;

                rc = fsi_slave_read(slave, off, buf + total_len, read_len);
                if (rc)
                        return rc;

                off += read_len;
        }

        return count;
}

static ssize_t fsi_slave_sysfs_raw_write(struct file *file,
                struct kobject *kobj, struct bin_attribute *attr,
                char *buf, loff_t off, size_t count)
{
        struct fsi_slave *slave = to_fsi_slave(kobj_to_dev(kobj));
        size_t total_len, write_len;
        int rc;

        if (off < 0)
                return -EINVAL;

        if (off > 0xffffffff || count > 0xffffffff || off + count > 0xffffffff)
                return -EINVAL;

        for (total_len = 0; total_len < count; total_len += write_len) {
                write_len = min_t(size_t, count, 4);
                write_len -= off & 0x3;

                rc = fsi_slave_write(slave, off, buf + total_len, write_len);
                if (rc)
                        return rc;

                off += write_len;
        }

        return count;
}

static const struct bin_attribute fsi_slave_raw_attr = {
        .attr = {
                .name = "raw",
                .mode = 0600,
        },
        .size = 0,
        .read = fsi_slave_sysfs_raw_read,
        .write = fsi_slave_sysfs_raw_write,
};

static ssize_t fsi_slave_sysfs_term_write(struct file *file,
                struct kobject *kobj, struct bin_attribute *attr,
                char *buf, loff_t off, size_t count)
{
        struct fsi_slave *slave = to_fsi_slave(kobj_to_dev(kobj));
        struct fsi_master *master = slave->master;

        if (!master->term)
                return -ENODEV;

        master->term(master, slave->link, slave->id);
        return count;
}

static const struct bin_attribute fsi_slave_term_attr = {
        .attr = {
                .name = "term",
                .mode = 0200,
        },
        .size = 0,
        .write = fsi_slave_sysfs_term_write,
};

/* Encode slave local bus echo delay */
static inline uint32_t fsi_smode_echodly(int x)
{
        return (x & FSI_SMODE_ED_MASK) << FSI_SMODE_ED_SHIFT;
}

/* Encode slave local bus send delay */
static inline uint32_t fsi_smode_senddly(int x)
{
        return (x & FSI_SMODE_SD_MASK) << FSI_SMODE_SD_SHIFT;
}

/* Encode slave local bus clock rate ratio */
static inline uint32_t fsi_smode_lbcrr(int x)
{
        return (x & FSI_SMODE_LBCRR_MASK) << FSI_SMODE_LBCRR_SHIFT;
}

/* Encode slave ID */
static inline uint32_t fsi_smode_sid(int x)
{
        return (x & FSI_SMODE_SID_MASK) << FSI_SMODE_SID_SHIFT;
}

static uint32_t fsi_slave_smode(int id)
{
        return FSI_SMODE_WSC | FSI_SMODE_ECRC
                | fsi_smode_sid(id)
                | fsi_smode_echodly(0xf) | fsi_smode_senddly(0xf)
                | fsi_smode_lbcrr(0x8);
}

static int fsi_slave_set_smode(struct fsi_master *master, int link, int id)
{
        uint32_t smode;

        /* set our smode register with the slave ID field to 0; this enables
         * extended slave addressing
         */
        smode = fsi_slave_smode(id);
        smode = cpu_to_be32(smode);

        return fsi_master_write(master, link, id, FSI_SLAVE_BASE + FSI_SMODE,
                        &smode, sizeof(smode));
}

static void fsi_slave_release(struct device *dev)
{
        struct fsi_slave *slave = to_fsi_slave(dev);

        of_node_put(dev->of_node);
        kfree(slave);
}

static bool fsi_slave_node_matches(struct device_node *np,
                int link, uint8_t id)
{
        unsigned int len, na, ns;
        const __be32 *prop;

        na = of_n_addr_cells(np);
        ns = of_n_size_cells(np);

        /* Ensure we have the correct format for addresses and sizes in
         * reg properties
         */
        if (na != 2 || ns != 0)
                return false;

        prop = of_get_property(np, "reg", &len);
        if (!prop || len != 8)
                return false;

        return (of_read_number(prop, 1) == link) &&
                (of_read_number(prop + 1, 1) == id);
}

/* Find a matching node for the slave at (link, id). Returns NULL if none
 * found, or a matching node with refcount already incremented.
 */
static struct device_node *fsi_slave_find_of_node(struct fsi_master *master,
                int link, uint8_t id)
{
        struct device_node *parent, *np;

        parent = dev_of_node(&master->dev);
        if (!parent)
                return NULL;

        for_each_child_of_node(parent, np) {
                if (fsi_slave_node_matches(np, link, id))
                        return np;
        }

        return NULL;
}

static int fsi_slave_init(struct fsi_master *master, int link, uint8_t id)
{
        uint32_t chip_id, llmode;
        struct fsi_slave *slave;
        uint8_t crc;
        int rc;

        /* Currently, we only support single slaves on a link, and use the
         * full 23-bit address range
         */
        if (id != 0)
                return -EINVAL;

        rc = fsi_master_read(master, link, id, 0, &chip_id, sizeof(chip_id));
        if (rc) {
                dev_dbg(&master->dev, "can't read slave %02x:%02x %d\n",
                                link, id, rc);
                return -ENODEV;
        }
        chip_id = be32_to_cpu(chip_id);

        crc = crc4(0, chip_id, 32);
        if (crc) {
                dev_warn(&master->dev, "slave %02x:%02x invalid chip id CRC!\n",
                                link, id);
                return -EIO;
        }

        dev_dbg(&master->dev, "fsi: found chip %08x at %02x:%02x:%02x\n",
                        chip_id, master->idx, link, id);

        rc = fsi_slave_set_smode(master, link, id);
        if (rc) {
                dev_warn(&master->dev,
                                "can't set smode on slave:%02x:%02x %d\n",
                                link, id, rc);
                return -ENODEV;
        }

        /* If we're behind a master that doesn't provide a self-running bus
         * clock, put the slave into async mode
         */
        if (master->flags & FSI_MASTER_FLAG_SWCLOCK) {
                llmode = cpu_to_be32(FSI_LLMODE_ASYNC);
                rc = fsi_master_write(master, link, id,
                                FSI_SLAVE_BASE + FSI_LLMODE,
                                &llmode, sizeof(llmode));
                if (rc)
                        dev_warn(&master->dev,
                                "can't set llmode on slave:%02x:%02x %d\n",
                                link, id, rc);
        }

        /* We can communicate with a slave; create the slave device and
         * register.
         */
        slave = kzalloc(sizeof(*slave), GFP_KERNEL);
        if (!slave)
                return -ENOMEM;

        slave->master = master;
        slave->dev.parent = &master->dev;
        slave->dev.of_node = fsi_slave_find_of_node(master, link, id);
        slave->dev.release = fsi_slave_release;
        slave->link = link;
        slave->id = id;
        slave->size = FSI_SLAVE_SIZE_23b;

        dev_set_name(&slave->dev, "slave@%02x:%02x", link, id);
        rc = device_register(&slave->dev);
        if (rc < 0) {
                dev_warn(&master->dev, "failed to create slave device: %d\n",
                                rc);
                put_device(&slave->dev);
                return rc;
        }

        rc = device_create_bin_file(&slave->dev, &fsi_slave_raw_attr);
        if (rc)
                dev_warn(&slave->dev, "failed to create raw attr: %d\n", rc);

        rc = device_create_bin_file(&slave->dev, &fsi_slave_term_attr);
        if (rc)
                dev_warn(&slave->dev, "failed to create term attr: %d\n", rc);

        rc = fsi_slave_scan(slave);
        if (rc)
                dev_dbg(&master->dev, "failed during slave scan with: %d\n",
                                rc);

        return rc;
}

/* FSI master support */
static int fsi_check_access(uint32_t addr, size_t size)
{
        if (size == 4) {
                if (addr & 0x3)
                        return -EINVAL;
        } else if (size == 2) {
                if (addr & 0x1)
                        return -EINVAL;
        } else if (size != 1)
                return -EINVAL;

        return 0;
}

static int fsi_master_read(struct fsi_master *master, int link,
                uint8_t slave_id, uint32_t addr, void *val, size_t size)
{
        int rc;

        trace_fsi_master_read(master, link, slave_id, addr, size);

        rc = fsi_check_access(addr, size);
        if (!rc)
                rc = master->read(master, link, slave_id, addr, val, size);

        trace_fsi_master_rw_result(master, link, slave_id, addr, size,
                        false, val, rc);

        return rc;
}

static int fsi_master_write(struct fsi_master *master, int link,
                uint8_t slave_id, uint32_t addr, const void *val, size_t size)
{
        int rc;

        trace_fsi_master_write(master, link, slave_id, addr, size, val);

        rc = fsi_check_access(addr, size);
        if (!rc)
                rc = master->write(master, link, slave_id, addr, val, size);

        trace_fsi_master_rw_result(master, link, slave_id, addr, size,
                        true, val, rc);

        return rc;
}

static int fsi_master_link_enable(struct fsi_master *master, int link)
{
        if (master->link_enable)
                return master->link_enable(master, link);

        return 0;
}

/*
 * Issue a break command on this link
 */
static int fsi_master_break(struct fsi_master *master, int link)
{
        trace_fsi_master_break(master, link);

        if (master->send_break)
                return master->send_break(master, link);

        return 0;
}

static int fsi_master_scan(struct fsi_master *master)
{
        int link, rc;

        for (link = 0; link < master->n_links; link++) {
                rc = fsi_master_link_enable(master, link);
                if (rc) {
                        dev_dbg(&master->dev,
                                "enable link %d failed: %d\n", link, rc);
                        continue;
                }
                rc = fsi_master_break(master, link);
                if (rc) {
                        dev_dbg(&master->dev,
                                "break to link %d failed: %d\n", link, rc);
                        continue;
                }

                fsi_slave_init(master, link, 0);
        }

        return 0;
}

static int fsi_slave_remove_device(struct device *dev, void *arg)
{
        device_unregister(dev);
        return 0;
}

static int fsi_master_remove_slave(struct device *dev, void *arg)
{
        device_for_each_child(dev, NULL, fsi_slave_remove_device);
        device_unregister(dev);
        return 0;
}

static void fsi_master_unscan(struct fsi_master *master)
{
        device_for_each_child(&master->dev, NULL, fsi_master_remove_slave);
}

int fsi_master_rescan(struct fsi_master *master)
{
        fsi_master_unscan(master);
        return fsi_master_scan(master);
}
EXPORT_SYMBOL_GPL(fsi_master_rescan);

static ssize_t master_rescan_store(struct device *dev,
                struct device_attribute *attr, const char *buf, size_t count)
{
        struct fsi_master *master = to_fsi_master(dev);
        int rc;

        rc = fsi_master_rescan(master);
        if (rc < 0)
                return rc;

        return count;
}

static DEVICE_ATTR(rescan, 0200, NULL, master_rescan_store);

static ssize_t master_break_store(struct device *dev,
                struct device_attribute *attr, const char *buf, size_t count)
{
        struct fsi_master *master = to_fsi_master(dev);

        fsi_master_break(master, 0);

        return count;
}

static DEVICE_ATTR(break, 0200, NULL, master_break_store);

int fsi_master_register(struct fsi_master *master)
{
        int rc;
        struct device_node *np;

        if (!master)
                return -EINVAL;

        master->idx = ida_simple_get(&master_ida, 0, INT_MAX, GFP_KERNEL);
        dev_set_name(&master->dev, "fsi%d", master->idx);

        rc = device_register(&master->dev);
        if (rc) {
                ida_simple_remove(&master_ida, master->idx);
                return rc;
        }

        rc = device_create_file(&master->dev, &dev_attr_rescan);
        if (rc) {
                device_unregister(&master->dev);
                ida_simple_remove(&master_ida, master->idx);
                return rc;
        }

        rc = device_create_file(&master->dev, &dev_attr_break);
        if (rc) {
                device_unregister(&master->dev);
                ida_simple_remove(&master_ida, master->idx);
                return rc;
        }

        np = dev_of_node(&master->dev);
        if (!of_property_read_bool(np, "no-scan-on-init"))
                fsi_master_scan(master);

        return 0;
}
EXPORT_SYMBOL_GPL(fsi_master_register);

void fsi_master_unregister(struct fsi_master *master)
{
        if (master->idx >= 0) {
                ida_simple_remove(&master_ida, master->idx);
                master->idx = -1;
        }

        fsi_master_unscan(master);
        device_unregister(&master->dev);
}
EXPORT_SYMBOL_GPL(fsi_master_unregister);

/* FSI core & Linux bus type definitions */

static int fsi_bus_match(struct device *dev, struct device_driver *drv)
{
        struct fsi_device *fsi_dev = to_fsi_dev(dev);
        struct fsi_driver *fsi_drv = to_fsi_drv(drv);
        const struct fsi_device_id *id;

        if (!fsi_drv->id_table)
                return 0;

        for (id = fsi_drv->id_table; id->engine_type; id++) {
                if (id->engine_type != fsi_dev->engine_type)
                        continue;
                if (id->version == FSI_VERSION_ANY ||
                                id->version == fsi_dev->version)
                        return 1;
        }

        return 0;
}

int fsi_driver_register(struct fsi_driver *fsi_drv)
{
        if (!fsi_drv)
                return -EINVAL;
        if (!fsi_drv->id_table)
                return -EINVAL;

        return driver_register(&fsi_drv->drv);
}
EXPORT_SYMBOL_GPL(fsi_driver_register);

void fsi_driver_unregister(struct fsi_driver *fsi_drv)
{
        driver_unregister(&fsi_drv->drv);
}
EXPORT_SYMBOL_GPL(fsi_driver_unregister);

struct bus_type fsi_bus_type = {
        .name           = "fsi",
        .match          = fsi_bus_match,
};
EXPORT_SYMBOL_GPL(fsi_bus_type);

static int __init fsi_init(void)
{
        return bus_register(&fsi_bus_type);
}

postcore_initcall(fsi_init);

static void fsi_exit(void)
{
        bus_unregister(&fsi_bus_type);
}
module_exit(fsi_exit);
module_param(discard_errors, int, 0664);
MODULE_LICENSE("GPL");
MODULE_PARM_DESC(discard_errors, "Don't invoke error handling on bus accesses");