/*
 * driver for channel subsystem
 *
 * Copyright IBM Corp. 2002, 2010
 *
 * Author(s): Arnd Bergmann (arndb@de.ibm.com)
 *            Cornelia Huck (cornelia.huck@de.ibm.com)
 */

#define KMSG_COMPONENT "cio"
#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt

#include <linux/module.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/list.h>
#include <linux/reboot.h>
#include <linux/suspend.h>
#include <linux/proc_fs.h>
#include <asm/isc.h>
#include <asm/crw.h>

#include "css.h"
#include "cio.h"
#include "cio_debug.h"
#include "ioasm.h"
#include "chsc.h"
#include "device.h"
#include "idset.h"
#include "chp.h"

int css_init_done = 0;
int max_ssid;

struct channel_subsystem *channel_subsystems[__MAX_CSSID + 1];
static struct bus_type css_bus_type;

int
for_each_subchannel(int(*fn)(struct subchannel_id, void *), void *data)
{
        struct subchannel_id schid;
        int ret;

        init_subchannel_id(&schid);
        do {
                do {
                        ret = fn(schid, data);
                        if (ret)
                                break;
                } while (schid.sch_no++ < __MAX_SUBCHANNEL);
                schid.sch_no = 0;
        } while (schid.ssid++ < max_ssid);
        return ret;
}

struct cb_data {
        void *data;
        struct idset *set;
        int (*fn_known_sch)(struct subchannel *, void *);
        int (*fn_unknown_sch)(struct subchannel_id, void *);
};

static int call_fn_known_sch(struct device *dev, void *data)
{
        struct subchannel *sch = to_subchannel(dev);
        struct cb_data *cb = data;
        int rc = 0;

        if (cb->set)
                idset_sch_del(cb->set, sch->schid);
        if (cb->fn_known_sch)
                rc = cb->fn_known_sch(sch, cb->data);
        return rc;
}

static int call_fn_unknown_sch(struct subchannel_id schid, void *data)
{
        struct cb_data *cb = data;
        int rc = 0;

        if (idset_sch_contains(cb->set, schid))
                rc = cb->fn_unknown_sch(schid, cb->data);
        return rc;
}

static int call_fn_all_sch(struct subchannel_id schid, void *data)
{
        struct cb_data *cb = data;
        struct subchannel *sch;
        int rc = 0;

        sch = get_subchannel_by_schid(schid);
        if (sch) {
                if (cb->fn_known_sch)
                        rc = cb->fn_known_sch(sch, cb->data);
                put_device(&sch->dev);
        } else {
                if (cb->fn_unknown_sch)
                        rc = cb->fn_unknown_sch(schid, cb->data);
        }

        return rc;
}

int for_each_subchannel_staged(int (*fn_known)(struct subchannel *, void *),
                               int (*fn_unknown)(struct subchannel_id,
                               void *), void *data)
{
        struct cb_data cb;
        int rc;

        cb.data = data;
        cb.fn_known_sch = fn_known;
        cb.fn_unknown_sch = fn_unknown;

        if (fn_known && !fn_unknown) {
                /* Skip idset allocation in case of known-only loop. */
                cb.set = NULL;
                return bus_for_each_dev(&css_bus_type, NULL, &cb,
                                        call_fn_known_sch);
        }

        cb.set = idset_sch_new();
        if (!cb.set)
                /* fall back to brute force scanning in case of oom */
                return for_each_subchannel(call_fn_all_sch, &cb);

        idset_fill(cb.set);

        /* Process registered subchannels. */
        rc = bus_for_each_dev(&css_bus_type, NULL, &cb, call_fn_known_sch);
        if (rc)
                goto out;
        /* Process unregistered subchannels. */
        if (fn_unknown)
                rc = for_each_subchannel(call_fn_unknown_sch, &cb);
out:
        idset_free(cb.set);

        return rc;
}

static void css_sch_todo(struct work_struct *work);

static int css_sch_create_locks(struct subchannel *sch)
{
        sch->lock = kmalloc(sizeof(*sch->lock), GFP_KERNEL);
        if (!sch->lock)
                return -ENOMEM;

        spin_lock_init(sch->lock);
        mutex_init(&sch->reg_mutex);

        return 0;
}

static void css_subchannel_release(struct device *dev)
{
        struct subchannel *sch = to_subchannel(dev);

        sch->config.intparm = 0;
        cio_commit_config(sch);
        kfree(sch->lock);
        kfree(sch);
}

struct subchannel *css_alloc_subchannel(struct subchannel_id schid)
{
        struct subchannel *sch;
        int ret;

        sch = kzalloc(sizeof(*sch), GFP_KERNEL | GFP_DMA);
        if (!sch)
                return ERR_PTR(-ENOMEM);

        ret = cio_validate_subchannel(sch, schid);
        if (ret < 0)
                goto err;

        ret = css_sch_create_locks(sch);
        if (ret)
                goto err;

        INIT_WORK(&sch->todo_work, css_sch_todo);
        sch->dev.release = &css_subchannel_release;
        device_initialize(&sch->dev);
        return sch;

err:
        kfree(sch);
        return ERR_PTR(ret);
}

static int css_sch_device_register(struct subchannel *sch)
{
        int ret;

        mutex_lock(&sch->reg_mutex);
        dev_set_name(&sch->dev, "0.%x.%04x", sch->schid.ssid,
                     sch->schid.sch_no);
        ret = device_add(&sch->dev);
        mutex_unlock(&sch->reg_mutex);
        return ret;
}

/**
 * css_sch_device_unregister - unregister a subchannel
 * @sch: subchannel to be unregistered
 */
void css_sch_device_unregister(struct subchannel *sch)
{
        mutex_lock(&sch->reg_mutex);
        if (device_is_registered(&sch->dev))
                device_unregister(&sch->dev);
        mutex_unlock(&sch->reg_mutex);
}
EXPORT_SYMBOL_GPL(css_sch_device_unregister);

static void ssd_from_pmcw(struct chsc_ssd_info *ssd, struct pmcw *pmcw)
{
        int i;
        int mask;

        memset(ssd, 0, sizeof(struct chsc_ssd_info));
        ssd->path_mask = pmcw->pim;
        for (i = 0; i < 8; i++) {
                mask = 0x80 >> i;
                if (pmcw->pim & mask) {
                        chp_id_init(&ssd->chpid[i]);
                        ssd->chpid[i].id = pmcw->chpid[i];
                }
        }
}

static void ssd_register_chpids(struct chsc_ssd_info *ssd)
{
        int i;
        int mask;

        for (i = 0; i < 8; i++) {
                mask = 0x80 >> i;
                if (ssd->path_mask & mask)
                        if (!chp_is_registered(ssd->chpid[i]))
                                chp_new(ssd->chpid[i]);
        }
}

void css_update_ssd_info(struct subchannel *sch)
{
        int ret;

        ret = chsc_get_ssd_info(sch->schid, &sch->ssd_info);
        if (ret)
                ssd_from_pmcw(&sch->ssd_info, &sch->schib.pmcw);

        ssd_register_chpids(&sch->ssd_info);
}

static ssize_t type_show(struct device *dev, struct device_attribute *attr,
                         char *buf)
{
        struct subchannel *sch = to_subchannel(dev);

        return sprintf(buf, "%01x\n", sch->st);
}

static DEVICE_ATTR(type, 0444, type_show, NULL);

static ssize_t modalias_show(struct device *dev, struct device_attribute *attr,
                             char *buf)
{
        struct subchannel *sch = to_subchannel(dev);

        return sprintf(buf, "css:t%01X\n", sch->st);
}

static DEVICE_ATTR(modalias, 0444, modalias_show, NULL);

static struct attribute *subch_attrs[] = {
        &dev_attr_type.attr,
        &dev_attr_modalias.attr,
        NULL,
};

static struct attribute_group subch_attr_group = {
        .attrs = subch_attrs,
};

static const struct attribute_group *default_subch_attr_groups[] = {
        &subch_attr_group,
        NULL,
};

int css_register_subchannel(struct subchannel *sch)
{
        int ret;

        /* Initialize the subchannel structure */
        sch->dev.parent = &channel_subsystems[0]->device;
        sch->dev.bus = &css_bus_type;
        sch->dev.groups = default_subch_attr_groups;
        /*
         * We don't want to generate uevents for I/O subchannels that don't
         * have a working ccw device behind them since they will be
         * unregistered before they can be used anyway, so we delay the add
         * uevent until after device recognition was successful.
         * Note that we suppress the uevent for all subchannel types;
         * the subchannel driver can decide itself when it wants to inform
         * userspace of its existence.
         */
        dev_set_uevent_suppress(&sch->dev, 1);
        css_update_ssd_info(sch);
        /* make it known to the system */
        ret = css_sch_device_register(sch);
        if (ret) {
                CIO_MSG_EVENT(0, "Could not register sch 0.%x.%04x: %d\n",
                              sch->schid.ssid, sch->schid.sch_no, ret);
                return ret;
        }
        if (!sch->driver) {
                /*
                 * No driver matched. Generate the uevent now so that
                 * a fitting driver module may be loaded based on the
                 * modalias.
                 */
                dev_set_uevent_suppress(&sch->dev, 0);
                kobject_uevent(&sch->dev.kobj, KOBJ_ADD);
        }
        return ret;
}

static int css_probe_device(struct subchannel_id schid)
{
        struct subchannel *sch;
        int ret;

        sch = css_alloc_subchannel(schid);
        if (IS_ERR(sch))
                return PTR_ERR(sch);

        ret = css_register_subchannel(sch);
        if (ret)
                put_device(&sch->dev);

        return ret;
}

static int
check_subchannel(struct device * dev, void * data)
{
        struct subchannel *sch;
        struct subchannel_id *schid = data;

        sch = to_subchannel(dev);
        return schid_equal(&sch->schid, schid);
}

struct subchannel *
get_subchannel_by_schid(struct subchannel_id schid)
{
        struct device *dev;

        dev = bus_find_device(&css_bus_type, NULL,
                              &schid, check_subchannel);

        return dev ? to_subchannel(dev) : NULL;
}

/**
 * css_sch_is_valid() - check if a subchannel is valid
 * @schib: subchannel information block for the subchannel
 */
int css_sch_is_valid(struct schib *schib)
{
        if ((schib->pmcw.st == SUBCHANNEL_TYPE_IO) && !schib->pmcw.dnv)
                return 0;
        if ((schib->pmcw.st == SUBCHANNEL_TYPE_MSG) && !schib->pmcw.w)
                return 0;
        return 1;
}
EXPORT_SYMBOL_GPL(css_sch_is_valid);

static int css_evaluate_new_subchannel(struct subchannel_id schid, int slow)
{
        struct schib schib;

        if (!slow) {
                /* Will be done on the slow path. */
                return -EAGAIN;
        }
        if (stsch(schid, &schib)) {
                /* Subchannel is not provided. */
                return -ENXIO;
        }
        if (!css_sch_is_valid(&schib)) {
                /* Unusable - ignore. */
                return 0;
        }
        CIO_MSG_EVENT(4, "event: sch 0.%x.%04x, new\n", schid.ssid,
                      schid.sch_no);

        return css_probe_device(schid);
}

static int css_evaluate_known_subchannel(struct subchannel *sch, int slow)
{
        int ret = 0;

        if (sch->driver) {
                if (sch->driver->sch_event)
                        ret = sch->driver->sch_event(sch, slow);
                else
                        dev_dbg(&sch->dev,
                                "Got subchannel machine check but "
                                "no sch_event handler provided.\n");
        }
        if (ret != 0 && ret != -EAGAIN) {
                CIO_MSG_EVENT(2, "eval: sch 0.%x.%04x, rc=%d\n",
                              sch->schid.ssid, sch->schid.sch_no, ret);
        }
        return ret;
}

static void css_evaluate_subchannel(struct subchannel_id schid, int slow)
{
        struct subchannel *sch;
        int ret;

        sch = get_subchannel_by_schid(schid);
        if (sch) {
                ret = css_evaluate_known_subchannel(sch, slow);
                put_device(&sch->dev);
        } else
                ret = css_evaluate_new_subchannel(schid, slow);
        if (ret == -EAGAIN)
                css_schedule_eval(schid);
}

/**
 * css_sched_sch_todo - schedule a subchannel operation
 * @sch: subchannel
 * @todo: todo
 *
 * Schedule the operation identified by @todo to be performed on the slow path
 * workqueue. Do nothing if another operation with higher priority is already
 * scheduled. Needs to be called with subchannel lock held.
 */
void css_sched_sch_todo(struct subchannel *sch, enum sch_todo todo)
{
        CIO_MSG_EVENT(4, "sch_todo: sched sch=0.%x.%04x todo=%d\n",
                      sch->schid.ssid, sch->schid.sch_no, todo);
        if (sch->todo >= todo)
                return;
        /* Get workqueue ref. */
        if (!get_device(&sch->dev))
                return;
        sch->todo = todo;
        if (!queue_work(cio_work_q, &sch->todo_work)) {
                /* Already queued, release workqueue ref. */
                put_device(&sch->dev);
        }
}
EXPORT_SYMBOL_GPL(css_sched_sch_todo);

static void css_sch_todo(struct work_struct *work)
{
        struct subchannel *sch;
        enum sch_todo todo;
        int ret;

        sch = container_of(work, struct subchannel, todo_work);
        /* Find out todo. */
        spin_lock_irq(sch->lock);
        todo = sch->todo;
        CIO_MSG_EVENT(4, "sch_todo: sch=0.%x.%04x, todo=%d\n", sch->schid.ssid,
                      sch->schid.sch_no, todo);
        sch->todo = SCH_TODO_NOTHING;
        spin_unlock_irq(sch->lock);
        /* Perform todo. */
        switch (todo) {
        case SCH_TODO_NOTHING:
                break;
        case SCH_TODO_EVAL:
                ret = css_evaluate_known_subchannel(sch, 1);
                if (ret == -EAGAIN) {
                        spin_lock_irq(sch->lock);
                        css_sched_sch_todo(sch, todo);
                        spin_unlock_irq(sch->lock);
                }
                break;
        case SCH_TODO_UNREG:
                css_sch_device_unregister(sch);
                break;
        }
        /* Release workqueue ref. */
        put_device(&sch->dev);
}

static struct idset *slow_subchannel_set;
static spinlock_t slow_subchannel_lock;
static wait_queue_head_t css_eval_wq;
static atomic_t css_eval_scheduled;

static int __init slow_subchannel_init(void)
{
        spin_lock_init(&slow_subchannel_lock);
        atomic_set(&css_eval_scheduled, 0);
        init_waitqueue_head(&css_eval_wq);
        slow_subchannel_set = idset_sch_new();
        if (!slow_subchannel_set) {
                CIO_MSG_EVENT(0, "could not allocate slow subchannel set\n");
                return -ENOMEM;
        }
        return 0;
}

static int slow_eval_known_fn(struct subchannel *sch, void *data)
{
        int eval;
        int rc;

        spin_lock_irq(&slow_subchannel_lock);
        eval = idset_sch_contains(slow_subchannel_set, sch->schid);
        idset_sch_del(slow_subchannel_set, sch->schid);
        spin_unlock_irq(&slow_subchannel_lock);
        if (eval) {
                rc = css_evaluate_known_subchannel(sch, 1);
                if (rc == -EAGAIN)
                        css_schedule_eval(sch->schid);
        }
        return 0;
}

static int slow_eval_unknown_fn(struct subchannel_id schid, void *data)
{
        int eval;
        int rc = 0;

        spin_lock_irq(&slow_subchannel_lock);
        eval = idset_sch_contains(slow_subchannel_set, schid);
        idset_sch_del(slow_subchannel_set, schid);
        spin_unlock_irq(&slow_subchannel_lock);
        if (eval) {
                rc = css_evaluate_new_subchannel(schid, 1);
                switch (rc) {
                case -EAGAIN:
                        css_schedule_eval(schid);
                        rc = 0;
                        break;
                case -ENXIO:
                case -ENOMEM:
                case -EIO:
                        /* These should abort looping */
                        spin_lock_irq(&slow_subchannel_lock);
                        idset_sch_del_subseq(slow_subchannel_set, schid);
                        spin_unlock_irq(&slow_subchannel_lock);
                        break;
                default:
                        rc = 0;
                }
                /* Allow scheduling here since the containing loop might
                 * take a while.  */
                cond_resched();
        }
        return rc;
}

static void css_slow_path_func(struct work_struct *unused)
{
        unsigned long flags;

        CIO_TRACE_EVENT(4, "slowpath");
        for_each_subchannel_staged(slow_eval_known_fn, slow_eval_unknown_fn,
                                   NULL);
        spin_lock_irqsave(&slow_subchannel_lock, flags);
        if (idset_is_empty(slow_subchannel_set)) {
                atomic_set(&css_eval_scheduled, 0);
                wake_up(&css_eval_wq);
        }
        spin_unlock_irqrestore(&slow_subchannel_lock, flags);
}

static DECLARE_DELAYED_WORK(slow_path_work, css_slow_path_func);
struct workqueue_struct *cio_work_q;

void css_schedule_eval(struct subchannel_id schid)
{
        unsigned long flags;

        spin_lock_irqsave(&slow_subchannel_lock, flags);
        idset_sch_add(slow_subchannel_set, schid);
        atomic_set(&css_eval_scheduled, 1);
        queue_delayed_work(cio_work_q, &slow_path_work, 0);
        spin_unlock_irqrestore(&slow_subchannel_lock, flags);
}

void css_schedule_eval_all(void)
{
        unsigned long flags;

        spin_lock_irqsave(&slow_subchannel_lock, flags);
        idset_fill(slow_subchannel_set);
        atomic_set(&css_eval_scheduled, 1);
        queue_delayed_work(cio_work_q, &slow_path_work, 0);
        spin_unlock_irqrestore(&slow_subchannel_lock, flags);
}

static int __unset_registered(struct device *dev, void *data)
{
        struct idset *set = data;
        struct subchannel *sch = to_subchannel(dev);

        idset_sch_del(set, sch->schid);
        return 0;
}

void css_schedule_eval_all_unreg(unsigned long delay)
{
        unsigned long flags;
        struct idset *unreg_set;

        /* Find unregistered subchannels. */
        unreg_set = idset_sch_new();
        if (!unreg_set) {
                /* Fallback. */
                css_schedule_eval_all();
                return;
        }
        idset_fill(unreg_set);
        bus_for_each_dev(&css_bus_type, NULL, unreg_set, __unset_registered);
        /* Apply to slow_subchannel_set. */
        spin_lock_irqsave(&slow_subchannel_lock, flags);
        idset_add_set(slow_subchannel_set, unreg_set);
        atomic_set(&css_eval_scheduled, 1);
        queue_delayed_work(cio_work_q, &slow_path_work, delay);
        spin_unlock_irqrestore(&slow_subchannel_lock, flags);
        idset_free(unreg_set);
}

void css_wait_for_slow_path(void)
{
        flush_workqueue(cio_work_q);
}

/* Schedule reprobing of all unregistered subchannels. */
void css_schedule_reprobe(void)
{
        /* Schedule with a delay to allow merging of subsequent calls. */
        css_schedule_eval_all_unreg(1 * HZ);
}
EXPORT_SYMBOL_GPL(css_schedule_reprobe);

/*
 * Called from the machine check handler for subchannel report words.
 */
static void css_process_crw(struct crw *crw0, struct crw *crw1, int overflow)
{
        struct subchannel_id mchk_schid;
        struct subchannel *sch;

        if (overflow) {
                css_schedule_eval_all();
                return;
        }
        CIO_CRW_EVENT(2, "CRW0 reports slct=%d, oflw=%d, "
                      "chn=%d, rsc=%X, anc=%d, erc=%X, rsid=%X\n",
                      crw0->slct, crw0->oflw, crw0->chn, crw0->rsc, crw0->anc,
                      crw0->erc, crw0->rsid);
        if (crw1)
                CIO_CRW_EVENT(2, "CRW1 reports slct=%d, oflw=%d, "
                              "chn=%d, rsc=%X, anc=%d, erc=%X, rsid=%X\n",
                              crw1->slct, crw1->oflw, crw1->chn, crw1->rsc,
                              crw1->anc, crw1->erc, crw1->rsid);
        init_subchannel_id(&mchk_schid);
        mchk_schid.sch_no = crw0->rsid;
        if (crw1)
                mchk_schid.ssid = (crw1->rsid >> 4) & 3;

        if (crw0->erc == CRW_ERC_PMOD) {
                sch = get_subchannel_by_schid(mchk_schid);
                if (sch) {
                        css_update_ssd_info(sch);
                        put_device(&sch->dev);
                }
        }
        /*
         * Since we are always presented with IPI in the CRW, we have to
         * use stsch() to find out if the subchannel in question has come
         * or gone.
         */
        css_evaluate_subchannel(mchk_schid, 0);
}

static void __init
css_generate_pgid(struct channel_subsystem *css, u32 tod_high)
{
        struct cpuid cpu_id;

        if (css_general_characteristics.mcss) {
                css->global_pgid.pgid_high.ext_cssid.version = 0x80;
                css->global_pgid.pgid_high.ext_cssid.cssid = css->cssid;
        } else {
                css->global_pgid.pgid_high.cpu_addr = stap();
        }
        get_cpu_id(&cpu_id);
        css->global_pgid.cpu_id = cpu_id.ident;
        css->global_pgid.cpu_model = cpu_id.machine;
        css->global_pgid.tod_high = tod_high;
}

static void
channel_subsystem_release(struct device *dev)
{
        struct channel_subsystem *css;

        css = to_css(dev);
        mutex_destroy(&css->mutex);
        if (css->pseudo_subchannel) {
                /* Implies that it has been generated but never registered. */
                css_subchannel_release(&css->pseudo_subchannel->dev);
                css->pseudo_subchannel = NULL;
        }
        kfree(css);
}

static ssize_t
css_cm_enable_show(struct device *dev, struct device_attribute *attr,
                   char *buf)
{
        struct channel_subsystem *css = to_css(dev);
        int ret;

        if (!css)
                return 0;
        mutex_lock(&css->mutex);
        ret = sprintf(buf, "%x\n", css->cm_enabled);
        mutex_unlock(&css->mutex);
        return ret;
}

static ssize_t
css_cm_enable_store(struct device *dev, struct device_attribute *attr,
                    const char *buf, size_t count)
{
        struct channel_subsystem *css = to_css(dev);
        int ret;
        unsigned long val;

        ret = kstrtoul(buf, 16, &val);
        if (ret)
                return ret;
        mutex_lock(&css->mutex);
        switch (val) {
        case 0:
                ret = css->cm_enabled ? chsc_secm(css, 0) : 0;
                break;
        case 1:
                ret = css->cm_enabled ? 0 : chsc_secm(css, 1);
                break;
        default:
                ret = -EINVAL;
        }
        mutex_unlock(&css->mutex);
        return ret < 0 ? ret : count;
}

static DEVICE_ATTR(cm_enable, 0644, css_cm_enable_show, css_cm_enable_store);

static int __init setup_css(int nr)
{
        u32 tod_high;
        int ret;
        struct channel_subsystem *css;

        css = channel_subsystems[nr];
        memset(css, 0, sizeof(struct channel_subsystem));
        css->pseudo_subchannel =
                kzalloc(sizeof(*css->pseudo_subchannel), GFP_KERNEL);
        if (!css->pseudo_subchannel)
                return -ENOMEM;
        css->pseudo_subchannel->dev.parent = &css->device;
        css->pseudo_subchannel->dev.release = css_subchannel_release;
        dev_set_name(&css->pseudo_subchannel->dev, "defunct");
        mutex_init(&css->pseudo_subchannel->reg_mutex);
        ret = css_sch_create_locks(css->pseudo_subchannel);
        if (ret) {
                kfree(css->pseudo_subchannel);
                return ret;
        }
        mutex_init(&css->mutex);
        css->valid = 1;
        css->cssid = nr;
        dev_set_name(&css->device, "css%x", nr);
        css->device.release = channel_subsystem_release;
        tod_high = (u32) (get_tod_clock() >> 32);
        css_generate_pgid(css, tod_high);
        return 0;
}

static int css_reboot_event(struct notifier_block *this,
                            unsigned long event,
                            void *ptr)
{
        int ret, i;

        ret = NOTIFY_DONE;
        for (i = 0; i <= __MAX_CSSID; i++) {
                struct channel_subsystem *css;

                css = channel_subsystems[i];
                mutex_lock(&css->mutex);
                if (css->cm_enabled)
                        if (chsc_secm(css, 0))
                                ret = NOTIFY_BAD;
                mutex_unlock(&css->mutex);
        }

        return ret;
}

static struct notifier_block css_reboot_notifier = {
        .notifier_call = css_reboot_event,
};

/*
 * Since the css devices are neither on a bus nor have a class
 * nor have a special device type, we cannot stop/restart channel
 * path measurements via the normal suspend/resume callbacks, but have
 * to use notifiers.
 */
static int css_power_event(struct notifier_block *this, unsigned long event,
                           void *ptr)
{
        int ret, i;

        switch (event) {
        case PM_HIBERNATION_PREPARE:
        case PM_SUSPEND_PREPARE:
                ret = NOTIFY_DONE;
                for (i = 0; i <= __MAX_CSSID; i++) {
                        struct channel_subsystem *css;

                        css = channel_subsystems[i];
                        mutex_lock(&css->mutex);
                        if (!css->cm_enabled) {
                                mutex_unlock(&css->mutex);
                                continue;
                        }
                        ret = __chsc_do_secm(css, 0);
                        ret = notifier_from_errno(ret);
                        mutex_unlock(&css->mutex);
                }
                break;
        case PM_POST_HIBERNATION:
        case PM_POST_SUSPEND:
                ret = NOTIFY_DONE;
                for (i = 0; i <= __MAX_CSSID; i++) {
                        struct channel_subsystem *css;

                        css = channel_subsystems[i];
                        mutex_lock(&css->mutex);
                        if (!css->cm_enabled) {
                                mutex_unlock(&css->mutex);
                                continue;
                        }
                        ret = __chsc_do_secm(css, 1);
                        ret = notifier_from_errno(ret);
                        mutex_unlock(&css->mutex);
                }
                /* search for subchannels, which appeared during hibernation */
                css_schedule_reprobe();
                break;
        default:
                ret = NOTIFY_DONE;
        }
        return ret;

}
static struct notifier_block css_power_notifier = {
        .notifier_call = css_power_event,
};

/*
 * Now that the driver core is running, we can setup our channel subsystem.
 * The struct subchannel's are created during probing.
 */
static int __init css_bus_init(void)
{
        int ret, i;

        ret = chsc_init();
        if (ret)
                return ret;

        chsc_determine_css_characteristics();
        /* Try to enable MSS. */
        ret = chsc_enable_facility(CHSC_SDA_OC_MSS);
        if (ret)
                max_ssid = 0;
        else /* Success. */
                max_ssid = __MAX_SSID;

        ret = slow_subchannel_init();
        if (ret)
                goto out;

        ret = crw_register_handler(CRW_RSC_SCH, css_process_crw);
        if (ret)
                goto out;

        if ((ret = bus_register(&css_bus_type)))
                goto out;

        /* Setup css structure. */
        for (i = 0; i <= __MAX_CSSID; i++) {
                struct channel_subsystem *css;

                css = kmalloc(sizeof(struct channel_subsystem), GFP_KERNEL);
                if (!css) {
                        ret = -ENOMEM;
                        goto out_unregister;
                }
                channel_subsystems[i] = css;
                ret = setup_css(i);
                if (ret) {
                        kfree(channel_subsystems[i]);
                        goto out_unregister;
                }
                ret = device_register(&css->device);
                if (ret) {
                        put_device(&css->device);
                        goto out_unregister;
                }
                if (css_chsc_characteristics.secm) {
                        ret = device_create_file(&css->device,
                                                 &dev_attr_cm_enable);
                        if (ret)
                                goto out_device;
                }
                ret = device_register(&css->pseudo_subchannel->dev);
                if (ret) {
                        put_device(&css->pseudo_subchannel->dev);
                        goto out_file;
                }
        }
        ret = register_reboot_notifier(&css_reboot_notifier);
        if (ret)
                goto out_unregister;
        ret = register_pm_notifier(&css_power_notifier);
        if (ret) {
                unregister_reboot_notifier(&css_reboot_notifier);
                goto out_unregister;
        }
        css_init_done = 1;

        /* Enable default isc for I/O subchannels. */
        isc_register(IO_SCH_ISC);

        return 0;
out_file:
        if (css_chsc_characteristics.secm)
                device_remove_file(&channel_subsystems[i]->device,
                                   &dev_attr_cm_enable);
out_device:
        device_unregister(&channel_subsystems[i]->device);
out_unregister:
        while (i > 0) {
                struct channel_subsystem *css;

                i--;
                css = channel_subsystems[i];
                device_unregister(&css->pseudo_subchannel->dev);
                css->pseudo_subchannel = NULL;
                if (css_chsc_characteristics.secm)
                        device_remove_file(&css->device,
                                           &dev_attr_cm_enable);
                device_unregister(&css->device);
        }
        bus_unregister(&css_bus_type);
out:
        crw_unregister_handler(CRW_RSC_SCH);
        idset_free(slow_subchannel_set);
        chsc_init_cleanup();
        pr_alert("The CSS device driver initialization failed with "
                 "errno=%d\n", ret);
        return ret;
}

static void __init css_bus_cleanup(void)
{
        struct channel_subsystem *css;
        int i;

        for (i = 0; i <= __MAX_CSSID; i++) {
                css = channel_subsystems[i];
                device_unregister(&css->pseudo_subchannel->dev);
                css->pseudo_subchannel = NULL;
                if (css_chsc_characteristics.secm)

                        device_remove_file(&css->device, &dev_attr_cm_enable);
                device_unregister(&css->device);
        }
        bus_unregister(&css_bus_type);
        crw_unregister_handler(CRW_RSC_SCH);
        idset_free(slow_subchannel_set);
        chsc_init_cleanup();
        isc_unregister(IO_SCH_ISC);
}

static int __init channel_subsystem_init(void)
{
        int ret;

        ret = css_bus_init();
        if (ret)
                return ret;
        cio_work_q = create_singlethread_workqueue("cio");
        if (!cio_work_q) {
                ret = -ENOMEM;
                goto out_bus;
        }
        ret = io_subchannel_init();
        if (ret)
                goto out_wq;

        return ret;
out_wq:
        destroy_workqueue(cio_work_q);
out_bus:
        css_bus_cleanup();
        return ret;
}
subsys_initcall(channel_subsystem_init);

static int css_settle(struct device_driver *drv, void *unused)
{
        struct css_driver *cssdrv = to_cssdriver(drv);

        if (cssdrv->settle)
                return cssdrv->settle();
        return 0;
}

int css_complete_work(void)
{
        int ret;

        /* Wait for the evaluation of subchannels to finish. */
        ret = wait_event_interruptible(css_eval_wq,
                                       atomic_read(&css_eval_scheduled) == 0);
        if (ret)
                return -EINTR;
        flush_workqueue(cio_work_q);
        /* Wait for the subchannel type specific initialization to finish */
        return bus_for_each_drv(&css_bus_type, NULL, NULL, css_settle);
}


/*
 * Wait for the initialization of devices to finish, to make sure we are
 * done with our setup if the search for the root device starts.
 */
static int __init channel_subsystem_init_sync(void)
{
        /* Register subchannels which are already in use. */
        cio_register_early_subchannels();
        /* Start initial subchannel evaluation. */
        css_schedule_eval_all();
        css_complete_work();
        return 0;
}
subsys_initcall_sync(channel_subsystem_init_sync);

void channel_subsystem_reinit(void)
{
        struct channel_path *chp;
        struct chp_id chpid;

        chsc_enable_facility(CHSC_SDA_OC_MSS);
        chp_id_for_each(&chpid) {
                chp = chpid_to_chp(chpid);
                if (chp)
                        chp_update_desc(chp);
        }
        cmf_reactivate();
}

#ifdef CONFIG_PROC_FS
static ssize_t cio_settle_write(struct file *file, const char __user *buf,
                                size_t count, loff_t *ppos)
{
        int ret;

        /* Handle pending CRW's. */
        crw_wait_for_channel_report();
        ret = css_complete_work();

        return ret ? ret : count;
}

static const struct file_operations cio_settle_proc_fops = {
        .open = nonseekable_open,
        .write = cio_settle_write,
        .llseek = no_llseek,
};

static int __init cio_settle_init(void)
{
        struct proc_dir_entry *entry;

        entry = proc_create("cio_settle", S_IWUSR, NULL,
                            &cio_settle_proc_fops);
        if (!entry)
                return -ENOMEM;
        return 0;
}
device_initcall(cio_settle_init);
#endif /*CONFIG_PROC_FS*/

int sch_is_pseudo_sch(struct subchannel *sch)
{
        return sch == to_css(sch->dev.parent)->pseudo_subchannel;
}

static int css_bus_match(struct device *dev, struct device_driver *drv)
{
        struct subchannel *sch = to_subchannel(dev);
        struct css_driver *driver = to_cssdriver(drv);
        struct css_device_id *id;

        for (id = driver->subchannel_type; id->match_flags; id++) {
                if (sch->st == id->type)
                        return 1;
        }

        return 0;
}

static int css_probe(struct device *dev)
{
        struct subchannel *sch;
        int ret;

        sch = to_subchannel(dev);
        sch->driver = to_cssdriver(dev->driver);
        ret = sch->driver->probe ? sch->driver->probe(sch) : 0;
        if (ret)
                sch->driver = NULL;
        return ret;
}

static int css_remove(struct device *dev)
{
        struct subchannel *sch;
        int ret;

        sch = to_subchannel(dev);
        ret = sch->driver->remove ? sch->driver->remove(sch) : 0;
        sch->driver = NULL;
        return ret;
}

static void css_shutdown(struct device *dev)
{
        struct subchannel *sch;

        sch = to_subchannel(dev);
        if (sch->driver && sch->driver->shutdown)
                sch->driver->shutdown(sch);
}

static int css_uevent(struct device *dev, struct kobj_uevent_env *env)
{
        struct subchannel *sch = to_subchannel(dev);
        int ret;

        ret = add_uevent_var(env, "ST=%01X", sch->st);
        if (ret)
                return ret;
        ret = add_uevent_var(env, "MODALIAS=css:t%01X", sch->st);
        return ret;
}

static int css_pm_prepare(struct device *dev)
{
        struct subchannel *sch = to_subchannel(dev);
        struct css_driver *drv;

        if (mutex_is_locked(&sch->reg_mutex))
                return -EAGAIN;
        if (!sch->dev.driver)
                return 0;
        drv = to_cssdriver(sch->dev.driver);
        /* Notify drivers that they may not register children. */
        return drv->prepare ? drv->prepare(sch) : 0;
}

static void css_pm_complete(struct device *dev)
{
        struct subchannel *sch = to_subchannel(dev);
        struct css_driver *drv;

        if (!sch->dev.driver)
                return;
        drv = to_cssdriver(sch->dev.driver);
        if (drv->complete)
                drv->complete(sch);
}

static int css_pm_freeze(struct device *dev)
{
        struct subchannel *sch = to_subchannel(dev);
        struct css_driver *drv;

        if (!sch->dev.driver)
                return 0;
        drv = to_cssdriver(sch->dev.driver);
        return drv->freeze ? drv->freeze(sch) : 0;
}

static int css_pm_thaw(struct device *dev)
{
        struct subchannel *sch = to_subchannel(dev);
        struct css_driver *drv;

        if (!sch->dev.driver)
                return 0;
        drv = to_cssdriver(sch->dev.driver);
        return drv->thaw ? drv->thaw(sch) : 0;
}

static int css_pm_restore(struct device *dev)
{
        struct subchannel *sch = to_subchannel(dev);
        struct css_driver *drv;

        css_update_ssd_info(sch);
        if (!sch->dev.driver)
                return 0;
        drv = to_cssdriver(sch->dev.driver);
        return drv->restore ? drv->restore(sch) : 0;
}

static const struct dev_pm_ops css_pm_ops = {
        .prepare = css_pm_prepare,
        .complete = css_pm_complete,
        .freeze = css_pm_freeze,
        .thaw = css_pm_thaw,
        .restore = css_pm_restore,
};

static struct bus_type css_bus_type = {
        .name     = "css",
        .match    = css_bus_match,
        .probe    = css_probe,
        .remove   = css_remove,
        .shutdown = css_shutdown,
        .uevent   = css_uevent,
        .pm = &css_pm_ops,
};

/**
 * css_driver_register - register a css driver
 * @cdrv: css driver to register
 *
 * This is mainly a wrapper around driver_register that sets name
 * and bus_type in the embedded struct device_driver correctly.
 */
int css_driver_register(struct css_driver *cdrv)
{
        cdrv->drv.bus = &css_bus_type;
        return driver_register(&cdrv->drv);
}
EXPORT_SYMBOL_GPL(css_driver_register);

/**
 * css_driver_unregister - unregister a css driver
 * @cdrv: css driver to unregister
 *
 * This is a wrapper around driver_unregister.
 */
void css_driver_unregister(struct css_driver *cdrv)
{
        driver_unregister(&cdrv->drv);
}
EXPORT_SYMBOL_GPL(css_driver_unregister);

MODULE_LICENSE("GPL");