css.c

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/*
 * driver for channel subsystem
 *
 * Copyright IBM Corp. 2002, 2010
 *
 * Author(s): Arnd Bergmann ([email protected])
 *        Cornelia Huck ([email protected])
 */

#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);
    ret = -ENODEV;
    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;

    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;

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

    sch = kmalloc (sizeof (*sch), GFP_KERNEL | GFP_DMA);
    if (sch == NULL)
        return ERR_PTR(-ENOMEM);
    ret = cio_validate_subchannel (sch, schid);
    if (ret < 0) {
        kfree(sch);
        return ERR_PTR(ret);
    }
    INIT_WORK(&sch->todo_work, css_sch_todo);
    return sch;
}

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

    sch = to_subchannel(dev);
    if (!cio_is_console(sch->schid)) {
        /* Reset intparm to zeroes. */
        sch->config.intparm = 0;
        cio_commit_config(sch);
        kfree(sch->lock);
        kfree(sch);
    }
}

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_register(&sch->dev);
    mutex_unlock(&sch->reg_mutex);
    return ret;
}

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;

    if (cio_is_console(sch->schid)) {
        /* Console is initialized too early for functions requiring
         * memory allocation. */
        ssd_from_pmcw(&sch->ssd_info, &sch->schib.pmcw);
    } else {
        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,
};

static 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.release = &css_subchannel_release;
    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;
}

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

    if (cio_is_console(schid))
        sch = cio_get_console_subchannel();
    else {
        sch = css_alloc_subchannel(schid);
        if (IS_ERR(sch))
            return PTR_ERR(sch);
    }
    ret = css_register_subchannel(sch);
    if (ret) {
        if (!cio_is_console(schid))
            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;
}

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_err(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);
}

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 */
            idset_sch_del_subseq(slow_subchannel_set, schid);
            break;
        default:
            rc = 0;
        }
    }
    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_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_work(cio_work_q, &slow_path_work);
    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_work(cio_work_q, &slow_path_work);
    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;
}

static void css_schedule_eval_all_unreg(void)
{
    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_work(cio_work_q, &slow_path_work);
    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)
{
    css_schedule_eval_all_unreg();
}
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 {
#ifdef CONFIG_SMP
        css->global_pgid.pgid_high.cpu_addr = stap();
#else
        css->global_pgid.pgid_high.cpu_addr = 0;
#endif
    }
    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 = strict_strtoul(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 = cio_create_sch_lock(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_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 (except for the
 * static console subchannel).
 */
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)
{
    /* 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)
            continue;
        chsc_determine_base_channel_path_desc(chpid, &chp->desc);
    }
}

#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,
};

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);

void css_driver_unregister(struct css_driver *cdrv)
{
    driver_unregister(&cdrv->drv);
}
EXPORT_SYMBOL_GPL(css_driver_unregister);

MODULE_LICENSE("GPL");