// SPDX-License-Identifier: GPL-2.0-only
/*
 * FSI core driver
 *
 * Copyright (C) IBM Corporation 2016
 *
 * TODO:
 *  - Rework topology
 *  - s/chip_id/chip_loc
 *  - s/cfam/chip (cfam_id -> chip_id etc...)
 */

#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/of_address.h>
#include <linux/of_device.h>
#include <linux/slab.h>
#include <linux/bitops.h>
#include <linux/cdev.h>
#include <linux/fs.h>
#include <linux/uaccess.h>

#include "fsi-master.h"
#include "fsi-slave.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_SLBUS               0x30    /* W  : LBUS Ownership */
#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 */

/*
 * SLBUS fields
 */
#define FSI_SLBUS_FORCE         0x80000000      /* Force LBUS ownership */

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

#define FSI_SLAVE_SIZE_23b              0x800000

static DEFINE_IDA(master_ida);

static const int slave_retries = 2;
static int discard_errors;

static dev_t fsi_base_dev;
static DEFINE_IDA(fsi_minor_ida);
#define FSI_CHAR_MAX_DEVICES    0x1000

/* Legacy /dev numbering: 4 devices per chip, 16 chips */
#define FSI_CHAR_LEGACY_TOP     64

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 core & Linux bus type definitions */

static int fsi_bus_match(struct device *dev, const struct device_driver *drv)
{
        struct fsi_device *fsi_dev = to_fsi_dev(dev);
        const 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) {
                        if (drv->of_match_table) {
                                if (of_driver_match_device(dev, drv))
                                        return 1;
                        } else {
                                return 1;
                        }
                }
        }

        return 0;
}

static int fsi_probe(struct device *dev)
{
        struct fsi_device *fsidev = to_fsi_dev(dev);
        struct fsi_driver *fsidrv = to_fsi_drv(dev->driver);

        if (fsidrv->probe)
                return fsidrv->probe(fsidev);
        else
                return 0;
}

static void fsi_remove(struct device *dev)
{
        struct fsi_device *fsidev = to_fsi_dev(dev);
        struct fsi_driver *fsidrv = to_fsi_drv(dev->driver);

        if (fsidrv->remove)
                fsidrv->remove(fsidev);
}

static const struct bus_type fsi_bus_type = {
        .name = "fsi",
        .match = fsi_bus_match,
        .probe = fsi_probe,
        .remove = fsi_remove,
};

/*
 * 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_obj(*dev);
        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;
        __be32 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));
}

/* 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, u8 t_senddly, u8 t_echodly)
{
        return FSI_SMODE_WSC | FSI_SMODE_ECRC
                | fsi_smode_sid(id)
                | fsi_smode_echodly(t_echodly - 1) | fsi_smode_senddly(t_senddly - 1)
                | fsi_smode_lbcrr(0x8);
}

static int fsi_slave_set_smode(struct fsi_slave *slave)
{
        uint32_t smode;
        __be32 data;

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

        return fsi_master_write(slave->master, slave->link, slave->id,
                                FSI_SLAVE_BASE + FSI_SMODE,
                                &data, sizeof(data));
}

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, send_delay, echo_delay;

        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;
                }
        }

        send_delay = slave->t_send_delay;
        echo_delay = slave->t_echo_delay;

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

        slave->t_send_delay = send_delay;
        slave->t_echo_delay = echo_delay;

        rc = fsi_slave_set_smode(slave);
        if (rc)
                return rc;

        if (master->link_config)
                master->link_config(master, link,
                                    slave->t_send_delay,
                                    slave->t_echo_delay);

        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);

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);

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)
{
        u64 paddr, psize;

        if (of_property_read_reg(np, 0, &paddr, &psize))
                return false;

        if (paddr != addr)
                return false;

        if (psize != size) {
                dev_warn(dev,
                        "node %pOF matches probed address, but not size (got 0x%llx, expected 0x%x)",
                        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;
        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;
                uint32_t conf;
                __be32 data;

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

                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;

                        trace_fsi_dev_init(dev);

                        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 unsigned long aligned_access_size(size_t offset, size_t count)
{
        unsigned long offset_unit, count_unit;

        /* Criteria:
         *
         * 1. Access size must be less than or equal to the maximum access
         *    width or the highest power-of-two factor of offset
         * 2. Access size must be less than or equal to the amount specified by
         *    count
         *
         * The access width is optimal if we can calculate 1 to be strictly
         * equal while still satisfying 2.
         */

        /* Find 1 by the bottom bit of offset (with a 4 byte access cap) */
        offset_unit = BIT(__builtin_ctzl(offset | 4));

        /* Find 2 by the top bit of count */
        count_unit = BIT(8 * sizeof(unsigned long) - 1 - __builtin_clzl(count));

        /* Constrain the maximum access width to the minimum of both criteria */
        return BIT(__builtin_ctzl(offset_unit | count_unit));
}

static ssize_t fsi_slave_sysfs_raw_read(struct file *file,
                struct kobject *kobj, const 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 = aligned_access_size(off, count - total_len);

                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, const 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 = aligned_access_size(off, count - total_len);

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

        fsi_free_minor(slave->dev.devt);
        of_node_put(dev->of_node);
        kfree(slave);
}

static bool fsi_slave_node_matches(struct device_node *np,
                int link, uint8_t id)
{
        u64 addr;

        if (of_property_read_reg(np, 0, &addr, NULL))
                return false;

        return addr == (((u64)link << 32) | 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 ssize_t cfam_read(struct file *filep, char __user *buf, size_t count,
                         loff_t *offset)
{
        struct fsi_slave *slave = filep->private_data;
        size_t total_len, read_len;
        loff_t off = *offset;
        ssize_t 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) {
                __be32 data;

                read_len = min_t(size_t, count, 4);
                read_len -= off & 0x3;

                rc = fsi_slave_read(slave, off, &data, read_len);
                if (rc)
                        goto fail;
                rc = copy_to_user(buf + total_len, &data, read_len);
                if (rc) {
                        rc = -EFAULT;
                        goto fail;
                }
                off += read_len;
        }
        rc = count;
 fail:
        *offset = off;
        return rc;
}

static ssize_t cfam_write(struct file *filep, const char __user *buf,
                          size_t count, loff_t *offset)
{
        struct fsi_slave *slave = filep->private_data;
        size_t total_len, write_len;
        loff_t off = *offset;
        ssize_t 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) {
                __be32 data;

                write_len = min_t(size_t, count, 4);
                write_len -= off & 0x3;

                rc = copy_from_user(&data, buf + total_len, write_len);
                if (rc) {
                        rc = -EFAULT;
                        goto fail;
                }
                rc = fsi_slave_write(slave, off, &data, write_len);
                if (rc)
                        goto fail;
                off += write_len;
        }
        rc = count;
 fail:
        *offset = off;
        return rc;
}

static loff_t cfam_llseek(struct file *file, loff_t offset, int whence)
{
        switch (whence) {
        case SEEK_CUR:
                break;
        case SEEK_SET:
                file->f_pos = offset;
                break;
        default:
                return -EINVAL;
        }

        return offset;
}

static int cfam_open(struct inode *inode, struct file *file)
{
        struct fsi_slave *slave = container_of(inode->i_cdev, struct fsi_slave, cdev);

        file->private_data = slave;

        return 0;
}

static const struct file_operations cfam_fops = {
        .owner          = THIS_MODULE,
        .open           = cfam_open,
        .llseek         = cfam_llseek,
        .read           = cfam_read,
        .write          = cfam_write,
};

static ssize_t send_term_store(struct device *dev,
                               struct device_attribute *attr,
                               const char *buf, size_t count)
{
        struct fsi_slave *slave = to_fsi_slave(dev);
        struct fsi_master *master = slave->master;

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

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

static DEVICE_ATTR_WO(send_term);

static ssize_t slave_send_echo_show(struct device *dev,
                                    struct device_attribute *attr,
                                    char *buf)
{
        struct fsi_slave *slave = to_fsi_slave(dev);

        return sprintf(buf, "%u\n", slave->t_send_delay);
}

static ssize_t slave_send_echo_store(struct device *dev,
                struct device_attribute *attr, const char *buf, size_t count)
{
        struct fsi_slave *slave = to_fsi_slave(dev);
        struct fsi_master *master = slave->master;
        unsigned long val;
        int rc;

        if (kstrtoul(buf, 0, &val) < 0)
                return -EINVAL;

        if (val < 1 || val > 16)
                return -EINVAL;

        if (!master->link_config)
                return -ENXIO;

        /* Current HW mandates that send and echo delay are identical */
        slave->t_send_delay = val;
        slave->t_echo_delay = val;

        rc = fsi_slave_set_smode(slave);
        if (rc < 0)
                return rc;
        if (master->link_config)
                master->link_config(master, slave->link,
                                    slave->t_send_delay,
                                    slave->t_echo_delay);

        return count;
}

static DEVICE_ATTR(send_echo_delays, 0600,
                   slave_send_echo_show, slave_send_echo_store);

static ssize_t chip_id_show(struct device *dev,
                            struct device_attribute *attr,
                            char *buf)
{
        struct fsi_slave *slave = to_fsi_slave(dev);

        return sprintf(buf, "%d\n", slave->chip_id);
}

static DEVICE_ATTR_RO(chip_id);

static ssize_t cfam_id_show(struct device *dev,
                            struct device_attribute *attr,
                            char *buf)
{
        struct fsi_slave *slave = to_fsi_slave(dev);

        return sprintf(buf, "0x%x\n", slave->cfam_id);
}

static DEVICE_ATTR_RO(cfam_id);

static struct attribute *cfam_attr[] = {
        &dev_attr_send_echo_delays.attr,
        &dev_attr_chip_id.attr,
        &dev_attr_cfam_id.attr,
        &dev_attr_send_term.attr,
        NULL,
};

static const struct attribute_group cfam_attr_group = {
        .attrs = cfam_attr,
};

static const struct attribute_group *cfam_attr_groups[] = {
        &cfam_attr_group,
        NULL,
};

static char *cfam_devnode(const struct device *dev, umode_t *mode,
                          kuid_t *uid, kgid_t *gid)
{
        const struct fsi_slave *slave = to_fsi_slave(dev);

#ifdef CONFIG_FSI_NEW_DEV_NODE
        return kasprintf(GFP_KERNEL, "fsi/cfam%d", slave->cdev_idx);
#else
        return kasprintf(GFP_KERNEL, "cfam%d", slave->cdev_idx);
#endif
}

static const struct device_type cfam_type = {
        .name = "cfam",
        .devnode = cfam_devnode,
        .groups = cfam_attr_groups
};

static char *fsi_cdev_devnode(const struct device *dev, umode_t *mode,
                              kuid_t *uid, kgid_t *gid)
{
#ifdef CONFIG_FSI_NEW_DEV_NODE
        return kasprintf(GFP_KERNEL, "fsi/%s", dev_name(dev));
#else
        return kasprintf(GFP_KERNEL, "%s", dev_name(dev));
#endif
}

const struct device_type fsi_cdev_type = {
        .name = "fsi-cdev",
        .devnode = fsi_cdev_devnode,
};
EXPORT_SYMBOL_GPL(fsi_cdev_type);

/* Backward compatible /dev/ numbering in "old style" mode */
static int fsi_adjust_index(int index)
{
#ifdef CONFIG_FSI_NEW_DEV_NODE
        return index;
#else
        return index + 1;
#endif
}

static int __fsi_get_new_minor(struct fsi_slave *slave, enum fsi_dev_type type,
                               dev_t *out_dev, int *out_index)
{
        int cid = slave->chip_id;
        int id;

        /* Check if we qualify for legacy numbering */
        if (cid >= 0 && cid < 16 && type < 4) {
                /*
                 * Try reserving the legacy number, which has 0 - 0x3f reserved
                 * in the ida range. cid goes up to 0xf and type contains two
                 * bits, so construct the id with the below two bit shift.
                 */
                id = (cid << 2) | type;
                id = ida_alloc_range(&fsi_minor_ida, id, id, GFP_KERNEL);
                if (id >= 0) {
                        *out_index = fsi_adjust_index(cid);
                        *out_dev = fsi_base_dev + id;
                        return 0;
                }
                /* Other failure */
                if (id != -ENOSPC)
                        return id;
                /* Fallback to non-legacy allocation */
        }
        id = ida_alloc_range(&fsi_minor_ida, FSI_CHAR_LEGACY_TOP,
                             FSI_CHAR_MAX_DEVICES - 1, GFP_KERNEL);
        if (id < 0)
                return id;
        *out_index = fsi_adjust_index(id);
        *out_dev = fsi_base_dev + id;
        return 0;
}

static const char *const fsi_dev_type_names[] = {
        "cfam",
        "sbefifo",
        "scom",
        "occ",
};

int fsi_get_new_minor(struct fsi_device *fdev, enum fsi_dev_type type,
                      dev_t *out_dev, int *out_index)
{
        if (fdev->dev.of_node) {
                int aid = of_alias_get_id(fdev->dev.of_node, fsi_dev_type_names[type]);

                if (aid >= 0) {
                        /* Use the same scheme as the legacy numbers. */
                        int id = (aid << 2) | type;

                        id = ida_alloc_range(&fsi_minor_ida, id, id, GFP_KERNEL);
                        if (id >= 0) {
                                *out_index = aid;
                                *out_dev = fsi_base_dev + id;
                                return 0;
                        }

                        if (id != -ENOSPC)
                                return id;
                }
        }

        return __fsi_get_new_minor(fdev->slave, type, out_dev, out_index);
}
EXPORT_SYMBOL_GPL(fsi_get_new_minor);

void fsi_free_minor(dev_t dev)
{
        ida_free(&fsi_minor_ida, MINOR(dev));
}
EXPORT_SYMBOL_GPL(fsi_free_minor);

static int fsi_slave_init(struct fsi_master *master, int link, uint8_t id)
{
        uint32_t cfam_id;
        struct fsi_slave *slave;
        uint8_t crc;
        __be32 data, llmode, slbus;
        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, &data, sizeof(data));
        if (rc) {
                dev_dbg(&master->dev, "can't read slave %02x:%02x %d\n",
                                link, id, rc);
                return -ENODEV;
        }
        cfam_id = be32_to_cpu(data);

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

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

        /* 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_obj(*slave);
        if (!slave)
                return -ENOMEM;

        dev_set_name(&slave->dev, "slave@%02x:%02x", link, id);
        slave->dev.type = &cfam_type;
        slave->dev.parent = &master->dev;
        slave->dev.of_node = fsi_slave_find_of_node(master, link, id);
        slave->dev.release = fsi_slave_release;
        device_initialize(&slave->dev);
        slave->cfam_id = cfam_id;
        slave->master = master;
        slave->link = link;
        slave->id = id;
        slave->size = FSI_SLAVE_SIZE_23b;
        slave->t_send_delay = 16;
        slave->t_echo_delay = 16;

        /* Get chip ID if any */
        slave->chip_id = -1;
        if (slave->dev.of_node) {
                uint32_t prop;
                if (!of_property_read_u32(slave->dev.of_node, "chip-id", &prop))
                        slave->chip_id = prop;

        }

        slbus = cpu_to_be32(FSI_SLBUS_FORCE);
        rc = fsi_master_write(master, link, id, FSI_SLAVE_BASE + FSI_SLBUS,
                              &slbus, sizeof(slbus));
        if (rc)
                dev_warn(&master->dev,
                         "can't set slbus on slave:%02x:%02x %d\n", link, id,
                         rc);

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

        /* Allocate a minor in the FSI space */
        rc = __fsi_get_new_minor(slave, fsi_dev_cfam, &slave->dev.devt,
                                 &slave->cdev_idx);
        if (rc)
                goto err_free;

        trace_fsi_slave_init(slave);

        /* Create chardev for userspace access */
        cdev_init(&slave->cdev, &cfam_fops);
        rc = cdev_device_add(&slave->cdev, &slave->dev);
        if (rc) {
                dev_err(&slave->dev, "Error %d creating slave device\n", rc);
                goto err_free_ida;
        }

        /* Now that we have the cdev registered with the core, any fatal
         * failures beyond this point will need to clean up through
         * cdev_device_del(). Fortunately though, nothing past here is fatal.
         */

        if (master->link_config)
                master->link_config(master, link,
                                    slave->t_send_delay,
                                    slave->t_echo_delay);

        /* Legacy raw file -> to be removed */
        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 = fsi_slave_scan(slave);
        if (rc)
                dev_dbg(&master->dev, "failed during slave scan with: %d\n",
                                rc);

        return 0;

err_free_ida:
        fsi_free_minor(slave->dev.devt);
err_free:
        of_node_put(slave->dev.of_node);
        kfree(slave);
        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_disable(struct fsi_master *master, int link)
{
        if (master->link_enable)
                return master->link_enable(master, link, false);

        return 0;
}

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

        return 0;
}

/*
 * Issue a break command on this link
 */
static int fsi_master_break(struct fsi_master *master, int link)
{
        int rc = 0;

        trace_fsi_master_break(master, link);

        if (master->send_break)
                rc = master->send_break(master, link);
        if (master->link_config)
                master->link_config(master, link, 16, 16);

        return rc;
}

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

        trace_fsi_master_scan(master, true);
        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) {
                        fsi_master_link_disable(master, link);
                        dev_dbg(&master->dev,
                                "break to link %d failed: %d\n", link, rc);
                        continue;
                }

                rc = fsi_slave_init(master, link, 0);
                if (rc)
                        fsi_master_link_disable(master, link);
        }

        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)
{
        struct fsi_slave *slave = to_fsi_slave(dev);

        device_for_each_child(dev, NULL, fsi_slave_remove_device);
        cdev_device_del(&slave->cdev, &slave->dev);
        put_device(dev);
        return 0;
}

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

int fsi_master_rescan(struct fsi_master *master)
{
        int rc;

        mutex_lock(&master->scan_lock);
        fsi_master_unscan(master);
        rc = fsi_master_scan(master);
        mutex_unlock(&master->scan_lock);

        return rc;
}
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);

static struct attribute *master_attrs[] = {
        &dev_attr_break.attr,
        &dev_attr_rescan.attr,
        NULL
};

ATTRIBUTE_GROUPS(master);

static struct class fsi_master_class = {
        .name = "fsi-master",
        .dev_groups = master_groups,
};

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

        mutex_init(&master->scan_lock);

        /* Alloc the requested index if it's non-zero */
        if (master->idx) {
                master->idx = ida_alloc_range(&master_ida, master->idx,
                                              master->idx, GFP_KERNEL);
        } else {
                master->idx = ida_alloc(&master_ida, GFP_KERNEL);
        }

        if (master->idx < 0)
                return master->idx;

        if (!dev_name(&master->dev))
                dev_set_name(&master->dev, "fsi%d", master->idx);

        master->dev.class = &fsi_master_class;

        mutex_lock(&master->scan_lock);
        rc = device_register(&master->dev);
        if (rc) {
                ida_free(&master_ida, master->idx);
                goto out;
        }

        np = dev_of_node(&master->dev);
        if (!of_property_read_bool(np, "no-scan-on-init")) {
                fsi_master_scan(master);
        }
out:
        mutex_unlock(&master->scan_lock);
        return rc;
}
EXPORT_SYMBOL_GPL(fsi_master_register);

void fsi_master_unregister(struct fsi_master *master)
{
        int idx = master->idx;

        trace_fsi_master_unregister(master);

        mutex_lock(&master->scan_lock);
        fsi_master_unscan(master);
        master->n_links = 0;
        mutex_unlock(&master->scan_lock);

        device_unregister(&master->dev);
        ida_free(&master_ida, idx);
}
EXPORT_SYMBOL_GPL(fsi_master_unregister);

static int fsi_legacy_probe(struct fsi_device *fsidev)
{
        struct device *dev = &fsidev->dev;
        struct device_driver *driver = dev->driver;

        return driver->probe(dev);
}

static void fsi_legacy_remove(struct fsi_device *fsidev)
{
        struct device *dev = &fsidev->dev;
        struct device_driver *driver = dev->driver;
        int ret;

        ret = driver->remove(dev);
        if (unlikely(ret))
                dev_warn(dev, "Ignoring return value of remove callback (%pe)\n", ERR_PTR(ret));
}

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

        fsi_drv->drv.bus = &fsi_bus_type;

        /*
         * This driver needs updating. Note that driver_register() warns about
         * this, so we're not adding another warning here.
         */
        if (!fsi_drv->probe && fsi_drv->drv.probe)
                fsi_drv->probe = fsi_legacy_probe;
        if (!fsi_drv->remove && fsi_drv->drv.remove)
                fsi_drv->remove = fsi_legacy_remove;

        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);

static int __init fsi_init(void)
{
        int rc;

        rc = alloc_chrdev_region(&fsi_base_dev, 0, FSI_CHAR_MAX_DEVICES, "fsi");
        if (rc)
                return rc;
        rc = bus_register(&fsi_bus_type);
        if (rc)
                goto fail_bus;

        rc = class_register(&fsi_master_class);
        if (rc)
                goto fail_class;

        return 0;

 fail_class:
        bus_unregister(&fsi_bus_type);
 fail_bus:
        unregister_chrdev_region(fsi_base_dev, FSI_CHAR_MAX_DEVICES);
        return rc;
}
postcore_initcall(fsi_init);

static void fsi_exit(void)
{
        class_unregister(&fsi_master_class);
        bus_unregister(&fsi_bus_type);
        unregister_chrdev_region(fsi_base_dev, FSI_CHAR_MAX_DEVICES);
        ida_destroy(&fsi_minor_ida);
}
module_exit(fsi_exit);
module_param(discard_errors, int, 0664);
MODULE_DESCRIPTION("FSI core driver");
MODULE_LICENSE("GPL");
MODULE_PARM_DESC(discard_errors, "Don't invoke error handling on bus accesses");