// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2012, The Linux Foundation. All rights reserved.
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/device.h>
#include <linux/io.h>
#include <linux/err.h>
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/mutex.h>
#include <linux/clk.h>
#include <linux/coresight.h>
#include <linux/of_platform.h>
#include <linux/delay.h>
#include <linux/pm_runtime.h>

#include "coresight-priv.h"

static DEFINE_MUTEX(coresight_mutex);

/**
 * struct coresight_node - elements of a path, from source to sink
 * @csdev:      Address of an element.
 * @link:       hook to the list.
 */
struct coresight_node {
        struct coresight_device *csdev;
        struct list_head link;
};

/*
 * When operating Coresight drivers from the sysFS interface, only a single
 * path can exist from a tracer (associated to a CPU) to a sink.
 */
static DEFINE_PER_CPU(struct list_head *, tracer_path);

/*
 * As of this writing only a single STM can be found in CS topologies.  Since
 * there is no way to know if we'll ever see more and what kind of
 * configuration they will enact, for the time being only define a single path
 * for STM.
 */
static struct list_head *stm_path;

/*
 * When losing synchronisation a new barrier packet needs to be inserted at the
 * beginning of the data collected in a buffer.  That way the decoder knows that
 * it needs to look for another sync sequence.
 */
const u32 barrier_pkt[5] = {0x7fffffff, 0x7fffffff,
                            0x7fffffff, 0x7fffffff, 0x0};

static int coresight_id_match(struct device *dev, void *data)
{
        int trace_id, i_trace_id;
        struct coresight_device *csdev, *i_csdev;

        csdev = data;
        i_csdev = to_coresight_device(dev);

        /*
         * No need to care about oneself and components that are not
         * sources or not enabled
         */
        if (i_csdev == csdev || !i_csdev->enable ||
            i_csdev->type != CORESIGHT_DEV_TYPE_SOURCE)
                return 0;

        /* Get the source ID for both compoment */
        trace_id = source_ops(csdev)->trace_id(csdev);
        i_trace_id = source_ops(i_csdev)->trace_id(i_csdev);

        /* All you need is one */
        if (trace_id == i_trace_id)
                return 1;

        return 0;
}

static int coresight_source_is_unique(struct coresight_device *csdev)
{
        int trace_id = source_ops(csdev)->trace_id(csdev);

        /* this shouldn't happen */
        if (trace_id < 0)
                return 0;

        return !bus_for_each_dev(&coresight_bustype, NULL,
                                 csdev, coresight_id_match);
}

static int coresight_find_link_inport(struct coresight_device *csdev,
                                      struct coresight_device *parent)
{
        int i;
        struct coresight_connection *conn;

        for (i = 0; i < parent->nr_outport; i++) {
                conn = &parent->conns[i];
                if (conn->child_dev == csdev)
                        return conn->child_port;
        }

        dev_err(&csdev->dev, "couldn't find inport, parent: %s, child: %s\n",
                dev_name(&parent->dev), dev_name(&csdev->dev));

        return 0;
}

static int coresight_find_link_outport(struct coresight_device *csdev,
                                       struct coresight_device *child)
{
        int i;
        struct coresight_connection *conn;

        for (i = 0; i < csdev->nr_outport; i++) {
                conn = &csdev->conns[i];
                if (conn->child_dev == child)
                        return conn->outport;
        }

        dev_err(&csdev->dev, "couldn't find outport, parent: %s, child: %s\n",
                dev_name(&csdev->dev), dev_name(&child->dev));

        return 0;
}

static int coresight_enable_sink(struct coresight_device *csdev, u32 mode)
{
        int ret;

        if (!csdev->enable) {
                if (sink_ops(csdev)->enable) {
                        ret = sink_ops(csdev)->enable(csdev, mode);
                        if (ret)
                                return ret;
                }
                csdev->enable = true;
        }

        atomic_inc(csdev->refcnt);

        return 0;
}

static void coresight_disable_sink(struct coresight_device *csdev)
{
        if (atomic_dec_return(csdev->refcnt) == 0) {
                if (sink_ops(csdev)->disable) {
                        sink_ops(csdev)->disable(csdev);
                        csdev->enable = false;
                }
        }
}

static int coresight_enable_link(struct coresight_device *csdev,
                                 struct coresight_device *parent,
                                 struct coresight_device *child)
{
        int ret;
        int link_subtype;
        int refport, inport, outport;

        if (!parent || !child)
                return -EINVAL;

        inport = coresight_find_link_inport(csdev, parent);
        outport = coresight_find_link_outport(csdev, child);
        link_subtype = csdev->subtype.link_subtype;

        if (link_subtype == CORESIGHT_DEV_SUBTYPE_LINK_MERG)
                refport = inport;
        else if (link_subtype == CORESIGHT_DEV_SUBTYPE_LINK_SPLIT)
                refport = outport;
        else
                refport = 0;

        if (atomic_inc_return(&csdev->refcnt[refport]) == 1) {
                if (link_ops(csdev)->enable) {
                        ret = link_ops(csdev)->enable(csdev, inport, outport);
                        if (ret)
                                return ret;
                }
        }

        csdev->enable = true;

        return 0;
}

static void coresight_disable_link(struct coresight_device *csdev,
                                   struct coresight_device *parent,
                                   struct coresight_device *child)
{
        int i, nr_conns;
        int link_subtype;
        int refport, inport, outport;

        if (!parent || !child)
                return;

        inport = coresight_find_link_inport(csdev, parent);
        outport = coresight_find_link_outport(csdev, child);
        link_subtype = csdev->subtype.link_subtype;

        if (link_subtype == CORESIGHT_DEV_SUBTYPE_LINK_MERG) {
                refport = inport;
                nr_conns = csdev->nr_inport;
        } else if (link_subtype == CORESIGHT_DEV_SUBTYPE_LINK_SPLIT) {
                refport = outport;
                nr_conns = csdev->nr_outport;
        } else {
                refport = 0;
                nr_conns = 1;
        }

        if (atomic_dec_return(&csdev->refcnt[refport]) == 0) {
                if (link_ops(csdev)->disable)
                        link_ops(csdev)->disable(csdev, inport, outport);
        }

        for (i = 0; i < nr_conns; i++)
                if (atomic_read(&csdev->refcnt[i]) != 0)
                        return;

        csdev->enable = false;
}

static int coresight_enable_source(struct coresight_device *csdev, u32 mode)
{
        int ret;

        if (!coresight_source_is_unique(csdev)) {
                dev_warn(&csdev->dev, "traceID %d not unique\n",
                         source_ops(csdev)->trace_id(csdev));
                return -EINVAL;
        }

        if (!csdev->enable) {
                if (source_ops(csdev)->enable) {
                        ret = source_ops(csdev)->enable(csdev, NULL, mode);
                        if (ret)
                                return ret;
                }
                csdev->enable = true;
        }

        atomic_inc(csdev->refcnt);

        return 0;
}

/**
 *  coresight_disable_source - Drop the reference count by 1 and disable
 *  the device if there are no users left.
 *
 *  @csdev - The coresight device to disable
 *
 *  Returns true if the device has been disabled.
 */
static bool coresight_disable_source(struct coresight_device *csdev)
{
        if (atomic_dec_return(csdev->refcnt) == 0) {
                if (source_ops(csdev)->disable)
                        source_ops(csdev)->disable(csdev, NULL);
                csdev->enable = false;
        }
        return !csdev->enable;
}

void coresight_disable_path(struct list_head *path)
{
        u32 type;
        struct coresight_node *nd;
        struct coresight_device *csdev, *parent, *child;

        list_for_each_entry(nd, path, link) {
                csdev = nd->csdev;
                type = csdev->type;

                /*
                 * ETF devices are tricky... They can be a link or a sink,
                 * depending on how they are configured.  If an ETF has been
                 * "activated" it will be configured as a sink, otherwise
                 * go ahead with the link configuration.
                 */
                if (type == CORESIGHT_DEV_TYPE_LINKSINK)
                        type = (csdev == coresight_get_sink(path)) ?
                                                CORESIGHT_DEV_TYPE_SINK :
                                                CORESIGHT_DEV_TYPE_LINK;

                switch (type) {
                case CORESIGHT_DEV_TYPE_SINK:
                        coresight_disable_sink(csdev);
                        break;
                case CORESIGHT_DEV_TYPE_SOURCE:
                        /* sources are disabled from either sysFS or Perf */
                        break;
                case CORESIGHT_DEV_TYPE_LINK:
                        parent = list_prev_entry(nd, link)->csdev;
                        child = list_next_entry(nd, link)->csdev;
                        coresight_disable_link(csdev, parent, child);
                        break;
                default:
                        break;
                }
        }
}

int coresight_enable_path(struct list_head *path, u32 mode)
{

        int ret = 0;
        u32 type;
        struct coresight_node *nd;
        struct coresight_device *csdev, *parent, *child;

        list_for_each_entry_reverse(nd, path, link) {
                csdev = nd->csdev;
                type = csdev->type;

                /*
                 * ETF devices are tricky... They can be a link or a sink,
                 * depending on how they are configured.  If an ETF has been
                 * "activated" it will be configured as a sink, otherwise
                 * go ahead with the link configuration.
                 */
                if (type == CORESIGHT_DEV_TYPE_LINKSINK)
                        type = (csdev == coresight_get_sink(path)) ?
                                                CORESIGHT_DEV_TYPE_SINK :
                                                CORESIGHT_DEV_TYPE_LINK;

                switch (type) {
                case CORESIGHT_DEV_TYPE_SINK:
                        ret = coresight_enable_sink(csdev, mode);
                        if (ret)
                                goto err;
                        break;
                case CORESIGHT_DEV_TYPE_SOURCE:
                        /* sources are enabled from either sysFS or Perf */
                        break;
                case CORESIGHT_DEV_TYPE_LINK:
                        parent = list_prev_entry(nd, link)->csdev;
                        child = list_next_entry(nd, link)->csdev;
                        ret = coresight_enable_link(csdev, parent, child);
                        if (ret)
                                goto err;
                        break;
                default:
                        goto err;
                }
        }

out:
        return ret;
err:
        coresight_disable_path(path);
        goto out;
}

struct coresight_device *coresight_get_sink(struct list_head *path)
{
        struct coresight_device *csdev;

        if (!path)
                return NULL;

        csdev = list_last_entry(path, struct coresight_node, link)->csdev;
        if (csdev->type != CORESIGHT_DEV_TYPE_SINK &&
            csdev->type != CORESIGHT_DEV_TYPE_LINKSINK)
                return NULL;

        return csdev;
}

static int coresight_enabled_sink(struct device *dev, const void *data)
{
        const bool *reset = data;
        struct coresight_device *csdev = to_coresight_device(dev);

        if ((csdev->type == CORESIGHT_DEV_TYPE_SINK ||
             csdev->type == CORESIGHT_DEV_TYPE_LINKSINK) &&
             csdev->activated) {
                /*
                 * Now that we have a handle on the sink for this session,
                 * disable the sysFS "enable_sink" flag so that possible
                 * concurrent perf session that wish to use another sink don't
                 * trip on it.  Doing so has no ramification for the current
                 * session.
                 */
                if (*reset)
                        csdev->activated = false;

                return 1;
        }

        return 0;
}

/**
 * coresight_get_enabled_sink - returns the first enabled sink found on the bus
 * @deactivate: Whether the 'enable_sink' flag should be reset
 *
 * When operated from perf the deactivate parameter should be set to 'true'.
 * That way the "enabled_sink" flag of the sink that was selected can be reset,
 * allowing for other concurrent perf sessions to choose a different sink.
 *
 * When operated from sysFS users have full control and as such the deactivate
 * parameter should be set to 'false', hence mandating users to explicitly
 * clear the flag.
 */
struct coresight_device *coresight_get_enabled_sink(bool deactivate)
{
        struct device *dev = NULL;

        dev = bus_find_device(&coresight_bustype, NULL, &deactivate,
                              coresight_enabled_sink);

        return dev ? to_coresight_device(dev) : NULL;
}

/**
 * _coresight_build_path - recursively build a path from a @csdev to a sink.
 * @csdev:      The device to start from.
 * @path:       The list to add devices to.
 *
 * The tree of Coresight device is traversed until an activated sink is
 * found.  From there the sink is added to the list along with all the
 * devices that led to that point - the end result is a list from source
 * to sink. In that list the source is the first device and the sink the
 * last one.
 */
static int _coresight_build_path(struct coresight_device *csdev,
                                 struct coresight_device *sink,
                                 struct list_head *path)
{
        int i;
        bool found = false;
        struct coresight_node *node;

        /* An activated sink has been found.  Enqueue the element */
        if (csdev == sink)
                goto out;

        /* Not a sink - recursively explore each port found on this element */
        for (i = 0; i < csdev->nr_outport; i++) {
                struct coresight_device *child_dev = csdev->conns[i].child_dev;

                if (child_dev &&
                    _coresight_build_path(child_dev, sink, path) == 0) {
                        found = true;
                        break;
                }
        }

        if (!found)
                return -ENODEV;

out:
        /*
         * A path from this element to a sink has been found.  The elements
         * leading to the sink are already enqueued, all that is left to do
         * is tell the PM runtime core we need this element and add a node
         * for it.
         */
        node = kzalloc(sizeof(struct coresight_node), GFP_KERNEL);
        if (!node)
                return -ENOMEM;

        node->csdev = csdev;
        list_add(&node->link, path);
        pm_runtime_get_sync(csdev->dev.parent);

        return 0;
}

struct list_head *coresight_build_path(struct coresight_device *source,
                                       struct coresight_device *sink)
{
        struct list_head *path;
        int rc;

        if (!sink)
                return ERR_PTR(-EINVAL);

        path = kzalloc(sizeof(struct list_head), GFP_KERNEL);
        if (!path)
                return ERR_PTR(-ENOMEM);

        INIT_LIST_HEAD(path);

        rc = _coresight_build_path(source, sink, path);
        if (rc) {
                kfree(path);
                return ERR_PTR(rc);
        }

        return path;
}

/**
 * coresight_release_path - release a previously built path.
 * @path:       the path to release.
 *
 * Go through all the elements of a path and 1) removed it from the list and
 * 2) free the memory allocated for each node.
 */
void coresight_release_path(struct list_head *path)
{
        struct coresight_device *csdev;
        struct coresight_node *nd, *next;

        list_for_each_entry_safe(nd, next, path, link) {
                csdev = nd->csdev;

                pm_runtime_put_sync(csdev->dev.parent);
                list_del(&nd->link);
                kfree(nd);
        }

        kfree(path);
        path = NULL;
}

/** coresight_validate_source - make sure a source has the right credentials
 *  @csdev:     the device structure for a source.
 *  @function:  the function this was called from.
 *
 * Assumes the coresight_mutex is held.
 */
static int coresight_validate_source(struct coresight_device *csdev,
                                     const char *function)
{
        u32 type, subtype;

        type = csdev->type;
        subtype = csdev->subtype.source_subtype;

        if (type != CORESIGHT_DEV_TYPE_SOURCE) {
                dev_err(&csdev->dev, "wrong device type in %s\n", function);
                return -EINVAL;
        }

        if (subtype != CORESIGHT_DEV_SUBTYPE_SOURCE_PROC &&
            subtype != CORESIGHT_DEV_SUBTYPE_SOURCE_SOFTWARE) {
                dev_err(&csdev->dev, "wrong device subtype in %s\n", function);
                return -EINVAL;
        }

        return 0;
}

int coresight_enable(struct coresight_device *csdev)
{
        int cpu, ret = 0;
        struct coresight_device *sink;
        struct list_head *path;
        enum coresight_dev_subtype_source subtype;

        subtype = csdev->subtype.source_subtype;

        mutex_lock(&coresight_mutex);

        ret = coresight_validate_source(csdev, __func__);
        if (ret)
                goto out;

        if (csdev->enable) {
                /*
                 * There could be multiple applications driving the software
                 * source. So keep the refcount for each such user when the
                 * source is already enabled.
                 */
                if (subtype == CORESIGHT_DEV_SUBTYPE_SOURCE_SOFTWARE)
                        atomic_inc(csdev->refcnt);
                goto out;
        }

        /*
         * Search for a valid sink for this session but don't reset the
         * "enable_sink" flag in sysFS.  Users get to do that explicitly.
         */
        sink = coresight_get_enabled_sink(false);
        if (!sink) {
                ret = -EINVAL;
                goto out;
        }

        path = coresight_build_path(csdev, sink);
        if (IS_ERR(path)) {
                pr_err("building path(s) failed\n");
                ret = PTR_ERR(path);
                goto out;
        }

        ret = coresight_enable_path(path, CS_MODE_SYSFS);
        if (ret)
                goto err_path;

        ret = coresight_enable_source(csdev, CS_MODE_SYSFS);
        if (ret)
                goto err_source;

        switch (subtype) {
        case CORESIGHT_DEV_SUBTYPE_SOURCE_PROC:
                /*
                 * When working from sysFS it is important to keep track
                 * of the paths that were created so that they can be
                 * undone in 'coresight_disable()'.  Since there can only
                 * be a single session per tracer (when working from sysFS)
                 * a per-cpu variable will do just fine.
                 */
                cpu = source_ops(csdev)->cpu_id(csdev);
                per_cpu(tracer_path, cpu) = path;
                break;
        case CORESIGHT_DEV_SUBTYPE_SOURCE_SOFTWARE:
                stm_path = path;
                break;
        default:
                /* We can't be here */
                break;
        }

out:
        mutex_unlock(&coresight_mutex);
        return ret;

err_source:
        coresight_disable_path(path);

err_path:
        coresight_release_path(path);
        goto out;
}
EXPORT_SYMBOL_GPL(coresight_enable);

void coresight_disable(struct coresight_device *csdev)
{
        int cpu, ret;
        struct list_head *path = NULL;

        mutex_lock(&coresight_mutex);

        ret = coresight_validate_source(csdev, __func__);
        if (ret)
                goto out;

        if (!csdev->enable || !coresight_disable_source(csdev))
                goto out;

        switch (csdev->subtype.source_subtype) {
        case CORESIGHT_DEV_SUBTYPE_SOURCE_PROC:
                cpu = source_ops(csdev)->cpu_id(csdev);
                path = per_cpu(tracer_path, cpu);
                per_cpu(tracer_path, cpu) = NULL;
                break;
        case CORESIGHT_DEV_SUBTYPE_SOURCE_SOFTWARE:
                path = stm_path;
                stm_path = NULL;
                break;
        default:
                /* We can't be here */
                break;
        }

        coresight_disable_path(path);
        coresight_release_path(path);

out:
        mutex_unlock(&coresight_mutex);
}
EXPORT_SYMBOL_GPL(coresight_disable);

static ssize_t enable_sink_show(struct device *dev,
                                struct device_attribute *attr, char *buf)
{
        struct coresight_device *csdev = to_coresight_device(dev);

        return scnprintf(buf, PAGE_SIZE, "%u\n", csdev->activated);
}

static ssize_t enable_sink_store(struct device *dev,
                                 struct device_attribute *attr,
                                 const char *buf, size_t size)
{
        int ret;
        unsigned long val;
        struct coresight_device *csdev = to_coresight_device(dev);

        ret = kstrtoul(buf, 10, &val);
        if (ret)
                return ret;

        if (val)
                csdev->activated = true;
        else
                csdev->activated = false;

        return size;

}
static DEVICE_ATTR_RW(enable_sink);

static ssize_t enable_source_show(struct device *dev,
                                  struct device_attribute *attr, char *buf)
{
        struct coresight_device *csdev = to_coresight_device(dev);

        return scnprintf(buf, PAGE_SIZE, "%u\n", csdev->enable);
}

static ssize_t enable_source_store(struct device *dev,
                                   struct device_attribute *attr,
                                   const char *buf, size_t size)
{
        int ret = 0;
        unsigned long val;
        struct coresight_device *csdev = to_coresight_device(dev);

        ret = kstrtoul(buf, 10, &val);
        if (ret)
                return ret;

        if (val) {
                ret = coresight_enable(csdev);
                if (ret)
                        return ret;
        } else {
                coresight_disable(csdev);
        }

        return size;
}
static DEVICE_ATTR_RW(enable_source);

static struct attribute *coresight_sink_attrs[] = {
        &dev_attr_enable_sink.attr,
        NULL,
};
ATTRIBUTE_GROUPS(coresight_sink);

static struct attribute *coresight_source_attrs[] = {
        &dev_attr_enable_source.attr,
        NULL,
};
ATTRIBUTE_GROUPS(coresight_source);

static struct device_type coresight_dev_type[] = {
        {
                .name = "none",
        },
        {
                .name = "sink",
                .groups = coresight_sink_groups,
        },
        {
                .name = "link",
        },
        {
                .name = "linksink",
                .groups = coresight_sink_groups,
        },
        {
                .name = "source",
                .groups = coresight_source_groups,
        },
};

static void coresight_device_release(struct device *dev)
{
        struct coresight_device *csdev = to_coresight_device(dev);

        kfree(csdev->conns);
        kfree(csdev->refcnt);
        kfree(csdev);
}

static int coresight_orphan_match(struct device *dev, void *data)
{
        int i;
        bool still_orphan = false;
        struct coresight_device *csdev, *i_csdev;
        struct coresight_connection *conn;

        csdev = data;
        i_csdev = to_coresight_device(dev);

        /* No need to check oneself */
        if (csdev == i_csdev)
                return 0;

        /* Move on to another component if no connection is orphan */
        if (!i_csdev->orphan)
                return 0;
        /*
         * Circle throuch all the connection of that component.  If we find
         * an orphan connection whose name matches @csdev, link it.
         */
        for (i = 0; i < i_csdev->nr_outport; i++) {
                conn = &i_csdev->conns[i];

                /* We have found at least one orphan connection */
                if (conn->child_dev == NULL) {
                        /* Does it match this newly added device? */
                        if (conn->child_name &&
                            !strcmp(dev_name(&csdev->dev), conn->child_name)) {
                                conn->child_dev = csdev;
                        } else {
                                /* This component still has an orphan */
                                still_orphan = true;
                        }
                }
        }

        i_csdev->orphan = still_orphan;

        /*
         * Returning '0' ensures that all known component on the
         * bus will be checked.
         */
        return 0;
}

static void coresight_fixup_orphan_conns(struct coresight_device *csdev)
{
        /*
         * No need to check for a return value as orphan connection(s)
         * are hooked-up with each newly added component.
         */
        bus_for_each_dev(&coresight_bustype, NULL,
                         csdev, coresight_orphan_match);
}


static void coresight_fixup_device_conns(struct coresight_device *csdev)
{
        int i;

        for (i = 0; i < csdev->nr_outport; i++) {
                struct coresight_connection *conn = &csdev->conns[i];
                struct device *dev = NULL;

                if (conn->child_name)
                        dev = bus_find_device_by_name(&coresight_bustype, NULL,
                                                      conn->child_name);
                if (dev) {
                        conn->child_dev = to_coresight_device(dev);
                        /* and put reference from 'bus_find_device()' */
                        put_device(dev);
                } else {
                        csdev->orphan = true;
                        conn->child_dev = NULL;
                }
        }
}

static int coresight_remove_match(struct device *dev, void *data)
{
        int i;
        struct coresight_device *csdev, *iterator;
        struct coresight_connection *conn;

        csdev = data;
        iterator = to_coresight_device(dev);

        /* No need to check oneself */
        if (csdev == iterator)
                return 0;

        /*
         * Circle throuch all the connection of that component.  If we find
         * a connection whose name matches @csdev, remove it.
         */
        for (i = 0; i < iterator->nr_outport; i++) {
                conn = &iterator->conns[i];

                if (conn->child_dev == NULL)
                        continue;

                if (!strcmp(dev_name(&csdev->dev), conn->child_name)) {
                        iterator->orphan = true;
                        conn->child_dev = NULL;
                        /* No need to continue */
                        break;
                }
        }

        /*
         * Returning '0' ensures that all known component on the
         * bus will be checked.
         */
        return 0;
}

static void coresight_remove_conns(struct coresight_device *csdev)
{
        bus_for_each_dev(&coresight_bustype, NULL,
                         csdev, coresight_remove_match);
}

/**
 * coresight_timeout - loop until a bit has changed to a specific state.
 * @addr: base address of the area of interest.
 * @offset: address of a register, starting from @addr.
 * @position: the position of the bit of interest.
 * @value: the value the bit should have.
 *
 * Return: 0 as soon as the bit has taken the desired state or -EAGAIN if
 * TIMEOUT_US has elapsed, which ever happens first.
 */

int coresight_timeout(void __iomem *addr, u32 offset, int position, int value)
{
        int i;
        u32 val;

        for (i = TIMEOUT_US; i > 0; i--) {
                val = __raw_readl(addr + offset);
                /* waiting on the bit to go from 0 to 1 */
                if (value) {
                        if (val & BIT(position))
                                return 0;
                /* waiting on the bit to go from 1 to 0 */
                } else {
                        if (!(val & BIT(position)))
                                return 0;
                }

                /*
                 * Delay is arbitrary - the specification doesn't say how long
                 * we are expected to wait.  Extra check required to make sure
                 * we don't wait needlessly on the last iteration.
                 */
                if (i - 1)
                        udelay(1);
        }

        return -EAGAIN;
}

struct bus_type coresight_bustype = {
        .name   = "coresight",
};

static int __init coresight_init(void)
{
        return bus_register(&coresight_bustype);
}
postcore_initcall(coresight_init);

struct coresight_device *coresight_register(struct coresight_desc *desc)
{
        int i;
        int ret;
        int link_subtype;
        int nr_refcnts = 1;
        atomic_t *refcnts = NULL;
        struct coresight_device *csdev;
        struct coresight_connection *conns = NULL;

        csdev = kzalloc(sizeof(*csdev), GFP_KERNEL);
        if (!csdev) {
                ret = -ENOMEM;
                goto err_kzalloc_csdev;
        }

        if (desc->type == CORESIGHT_DEV_TYPE_LINK ||
            desc->type == CORESIGHT_DEV_TYPE_LINKSINK) {
                link_subtype = desc->subtype.link_subtype;

                if (link_subtype == CORESIGHT_DEV_SUBTYPE_LINK_MERG)
                        nr_refcnts = desc->pdata->nr_inport;
                else if (link_subtype == CORESIGHT_DEV_SUBTYPE_LINK_SPLIT)
                        nr_refcnts = desc->pdata->nr_outport;
        }

        refcnts = kcalloc(nr_refcnts, sizeof(*refcnts), GFP_KERNEL);
        if (!refcnts) {
                ret = -ENOMEM;
                goto err_kzalloc_refcnts;
        }

        csdev->refcnt = refcnts;

        csdev->nr_inport = desc->pdata->nr_inport;
        csdev->nr_outport = desc->pdata->nr_outport;

        /* Initialise connections if there is at least one outport */
        if (csdev->nr_outport) {
                conns = kcalloc(csdev->nr_outport, sizeof(*conns), GFP_KERNEL);
                if (!conns) {
                        ret = -ENOMEM;
                        goto err_kzalloc_conns;
                }

                for (i = 0; i < csdev->nr_outport; i++) {

                        conns[i].outport = desc->pdata->outports[i];
                        conns[i].child_name = desc->pdata->child_names[i];
                        conns[i].child_port = desc->pdata->child_ports[i];
                }
        }

        csdev->conns = conns;

        csdev->type = desc->type;
        csdev->subtype = desc->subtype;
        csdev->ops = desc->ops;
        csdev->orphan = false;

        csdev->dev.type = &coresight_dev_type[desc->type];
        csdev->dev.groups = desc->groups;
        csdev->dev.parent = desc->dev;
        csdev->dev.release = coresight_device_release;
        csdev->dev.bus = &coresight_bustype;
        dev_set_name(&csdev->dev, "%s", desc->pdata->name);

        ret = device_register(&csdev->dev);
        if (ret) {
                put_device(&csdev->dev);
                goto err_kzalloc_csdev;
        }

        mutex_lock(&coresight_mutex);

        coresight_fixup_device_conns(csdev);
        coresight_fixup_orphan_conns(csdev);

        mutex_unlock(&coresight_mutex);

        return csdev;

err_kzalloc_conns:
        kfree(refcnts);
err_kzalloc_refcnts:
        kfree(csdev);
err_kzalloc_csdev:
        return ERR_PTR(ret);
}
EXPORT_SYMBOL_GPL(coresight_register);

void coresight_unregister(struct coresight_device *csdev)
{
        /* Remove references of that device in the topology */
        coresight_remove_conns(csdev);
        device_unregister(&csdev->dev);
}
EXPORT_SYMBOL_GPL(coresight_unregister);