sclp.c

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/*
 * core function to access sclp interface
 *
 * Copyright IBM Corp. 1999, 2009
 *
 * Author(s): Martin Peschke <[email protected]>
 *        Martin Schwidefsky <[email protected]>
 */

#include <linux/kernel_stat.h>
#include <linux/module.h>
#include <linux/err.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/timer.h>
#include <linux/reboot.h>
#include <linux/jiffies.h>
#include <linux/init.h>
#include <linux/suspend.h>
#include <linux/completion.h>
#include <linux/platform_device.h>
#include <asm/types.h>
#include <asm/irq.h>

#include "sclp.h"

#define SCLP_HEADER     "sclp: "

/* Lock to protect internal data consistency. */
static DEFINE_SPINLOCK(sclp_lock);

/* Mask of events that we can send to the sclp interface. */
static sccb_mask_t sclp_receive_mask;

/* Mask of events that we can receive from the sclp interface. */
static sccb_mask_t sclp_send_mask;

/* List of registered event listeners and senders. */
static struct list_head sclp_reg_list;

/* List of queued requests. */
static struct list_head sclp_req_queue;

/* Data for read and and init requests. */
static struct sclp_req sclp_read_req;
static struct sclp_req sclp_init_req;
static char sclp_read_sccb[PAGE_SIZE] __attribute__((__aligned__(PAGE_SIZE)));
static char sclp_init_sccb[PAGE_SIZE] __attribute__((__aligned__(PAGE_SIZE)));

/* Suspend request */
static DECLARE_COMPLETION(sclp_request_queue_flushed);

static void sclp_suspend_req_cb(struct sclp_req *req, void *data)
{
    complete(&sclp_request_queue_flushed);
}

static struct sclp_req sclp_suspend_req;

/* Timer for request retries. */
static struct timer_list sclp_request_timer;

/* Internal state: is the driver initialized? */
static volatile enum sclp_init_state_t {
    sclp_init_state_uninitialized,
    sclp_init_state_initializing,
    sclp_init_state_initialized
} sclp_init_state = sclp_init_state_uninitialized;

/* Internal state: is a request active at the sclp? */
static volatile enum sclp_running_state_t {
    sclp_running_state_idle,
    sclp_running_state_running,
    sclp_running_state_reset_pending
} sclp_running_state = sclp_running_state_idle;

/* Internal state: is a read request pending? */
static volatile enum sclp_reading_state_t {
    sclp_reading_state_idle,
    sclp_reading_state_reading
} sclp_reading_state = sclp_reading_state_idle;

/* Internal state: is the driver currently serving requests? */
static volatile enum sclp_activation_state_t {
    sclp_activation_state_active,
    sclp_activation_state_deactivating,
    sclp_activation_state_inactive,
    sclp_activation_state_activating
} sclp_activation_state = sclp_activation_state_active;

/* Internal state: is an init mask request pending? */
static volatile enum sclp_mask_state_t {
    sclp_mask_state_idle,
    sclp_mask_state_initializing
} sclp_mask_state = sclp_mask_state_idle;

/* Internal state: is the driver suspended? */
static enum sclp_suspend_state_t {
    sclp_suspend_state_running,
    sclp_suspend_state_suspended,
} sclp_suspend_state = sclp_suspend_state_running;

/* Maximum retry counts */
#define SCLP_INIT_RETRY     3
#define SCLP_MASK_RETRY     3

/* Timeout intervals in seconds.*/
#define SCLP_BUSY_INTERVAL  10
#define SCLP_RETRY_INTERVAL 30

static void sclp_process_queue(void);
static void __sclp_make_read_req(void);
static int sclp_init_mask(int calculate);
static int sclp_init(void);

/* Perform service call. Return 0 on success, non-zero otherwise. */
int
sclp_service_call(sclp_cmdw_t command, void *sccb)
{
    int cc;

    asm volatile(
        "   .insn   rre,0xb2200000,%1,%2\n"  /* servc %1,%2 */
        "   ipm %0\n"
        "   srl %0,28"
        : "=&d" (cc) : "d" (command), "a" (__pa(sccb))
        : "cc", "memory");
    if (cc == 3)
        return -EIO;
    if (cc == 2)
        return -EBUSY;
    return 0;
}


static void
__sclp_queue_read_req(void)
{
    if (sclp_reading_state == sclp_reading_state_idle) {
        sclp_reading_state = sclp_reading_state_reading;
        __sclp_make_read_req();
        /* Add request to head of queue */
        list_add(&sclp_read_req.list, &sclp_req_queue);
    }
}

/* Set up request retry timer. Called while sclp_lock is locked. */
static inline void
__sclp_set_request_timer(unsigned long time, void (*function)(unsigned long),
             unsigned long data)
{
    del_timer(&sclp_request_timer);
    sclp_request_timer.function = function;
    sclp_request_timer.data = data;
    sclp_request_timer.expires = jiffies + time;
    add_timer(&sclp_request_timer);
}

/* Request timeout handler. Restart the request queue. If DATA is non-zero,
 * force restart of running request. */
static void
sclp_request_timeout(unsigned long data)
{
    unsigned long flags;

    spin_lock_irqsave(&sclp_lock, flags);
    if (data) {
        if (sclp_running_state == sclp_running_state_running) {
            /* Break running state and queue NOP read event request
             * to get a defined interface state. */
            __sclp_queue_read_req();
            sclp_running_state = sclp_running_state_idle;
        }
    } else {
        __sclp_set_request_timer(SCLP_BUSY_INTERVAL * HZ,
                     sclp_request_timeout, 0);
    }
    spin_unlock_irqrestore(&sclp_lock, flags);
    sclp_process_queue();
}

/* Try to start a request. Return zero if the request was successfully
 * started or if it will be started at a later time. Return non-zero otherwise.
 * Called while sclp_lock is locked. */
static int
__sclp_start_request(struct sclp_req *req)
{
    int rc;

    if (sclp_running_state != sclp_running_state_idle)
        return 0;
    del_timer(&sclp_request_timer);
    rc = sclp_service_call(req->command, req->sccb);
    req->start_count++;

    if (rc == 0) {
        /* Successfully started request */
        req->status = SCLP_REQ_RUNNING;
        sclp_running_state = sclp_running_state_running;
        __sclp_set_request_timer(SCLP_RETRY_INTERVAL * HZ,
                     sclp_request_timeout, 1);
        return 0;
    } else if (rc == -EBUSY) {
        /* Try again later */
        __sclp_set_request_timer(SCLP_BUSY_INTERVAL * HZ,
                     sclp_request_timeout, 0);
        return 0;
    }
    /* Request failed */
    req->status = SCLP_REQ_FAILED;
    return rc;
}

/* Try to start queued requests. */
static void
sclp_process_queue(void)
{
    struct sclp_req *req;
    int rc;
    unsigned long flags;

    spin_lock_irqsave(&sclp_lock, flags);
    if (sclp_running_state != sclp_running_state_idle) {
        spin_unlock_irqrestore(&sclp_lock, flags);
        return;
    }
    del_timer(&sclp_request_timer);
    while (!list_empty(&sclp_req_queue)) {
        req = list_entry(sclp_req_queue.next, struct sclp_req, list);
        if (!req->sccb)
            goto do_post;
        rc = __sclp_start_request(req);
        if (rc == 0)
            break;
        /* Request failed */
        if (req->start_count > 1) {
            /* Cannot abort already submitted request - could still
             * be active at the SCLP */
            __sclp_set_request_timer(SCLP_BUSY_INTERVAL * HZ,
                         sclp_request_timeout, 0);
            break;
        }
do_post:
        /* Post-processing for aborted request */
        list_del(&req->list);
        if (req->callback) {
            spin_unlock_irqrestore(&sclp_lock, flags);
            req->callback(req, req->callback_data);
            spin_lock_irqsave(&sclp_lock, flags);
        }
    }
    spin_unlock_irqrestore(&sclp_lock, flags);
}

static int __sclp_can_add_request(struct sclp_req *req)
{
    if (req == &sclp_suspend_req || req == &sclp_init_req)
        return 1;
    if (sclp_suspend_state != sclp_suspend_state_running)
        return 0;
    if (sclp_init_state != sclp_init_state_initialized)
        return 0;
    if (sclp_activation_state != sclp_activation_state_active)
        return 0;
    return 1;
}

/* Queue a new request. Return zero on success, non-zero otherwise. */
int
sclp_add_request(struct sclp_req *req)
{
    unsigned long flags;
    int rc;

    spin_lock_irqsave(&sclp_lock, flags);
    if (!__sclp_can_add_request(req)) {
        spin_unlock_irqrestore(&sclp_lock, flags);
        return -EIO;
    }
    req->status = SCLP_REQ_QUEUED;
    req->start_count = 0;
    list_add_tail(&req->list, &sclp_req_queue);
    rc = 0;
    /* Start if request is first in list */
    if (sclp_running_state == sclp_running_state_idle &&
        req->list.prev == &sclp_req_queue) {
        if (!req->sccb) {
            list_del(&req->list);
            rc = -ENODATA;
            goto out;
        }
        rc = __sclp_start_request(req);
        if (rc)
            list_del(&req->list);
    }
out:
    spin_unlock_irqrestore(&sclp_lock, flags);
    return rc;
}

EXPORT_SYMBOL(sclp_add_request);

/* Dispatch events found in request buffer to registered listeners. Return 0
 * if all events were dispatched, non-zero otherwise. */
static int
sclp_dispatch_evbufs(struct sccb_header *sccb)
{
    unsigned long flags;
    struct evbuf_header *evbuf;
    struct list_head *l;
    struct sclp_register *reg;
    int offset;
    int rc;

    spin_lock_irqsave(&sclp_lock, flags);
    rc = 0;
    for (offset = sizeof(struct sccb_header); offset < sccb->length;
         offset += evbuf->length) {
        evbuf = (struct evbuf_header *) ((addr_t) sccb + offset);
        /* Check for malformed hardware response */
        if (evbuf->length == 0)
            break;
        /* Search for event handler */
        reg = NULL;
        list_for_each(l, &sclp_reg_list) {
            reg = list_entry(l, struct sclp_register, list);
            if (reg->receive_mask & (1 << (32 - evbuf->type)))
                break;
            else
                reg = NULL;
        }
        if (reg && reg->receiver_fn) {
            spin_unlock_irqrestore(&sclp_lock, flags);
            reg->receiver_fn(evbuf);
            spin_lock_irqsave(&sclp_lock, flags);
        } else if (reg == NULL)
            rc = -EOPNOTSUPP;
    }
    spin_unlock_irqrestore(&sclp_lock, flags);
    return rc;
}

/* Read event data request callback. */
static void
sclp_read_cb(struct sclp_req *req, void *data)
{
    unsigned long flags;
    struct sccb_header *sccb;

    sccb = (struct sccb_header *) req->sccb;
    if (req->status == SCLP_REQ_DONE && (sccb->response_code == 0x20 ||
        sccb->response_code == 0x220))
        sclp_dispatch_evbufs(sccb);
    spin_lock_irqsave(&sclp_lock, flags);
    sclp_reading_state = sclp_reading_state_idle;
    spin_unlock_irqrestore(&sclp_lock, flags);
}

/* Prepare read event data request. Called while sclp_lock is locked. */
static void __sclp_make_read_req(void)
{
    struct sccb_header *sccb;

    sccb = (struct sccb_header *) sclp_read_sccb;
    clear_page(sccb);
    memset(&sclp_read_req, 0, sizeof(struct sclp_req));
    sclp_read_req.command = SCLP_CMDW_READ_EVENT_DATA;
    sclp_read_req.status = SCLP_REQ_QUEUED;
    sclp_read_req.start_count = 0;
    sclp_read_req.callback = sclp_read_cb;
    sclp_read_req.sccb = sccb;
    sccb->length = PAGE_SIZE;
    sccb->function_code = 0;
    sccb->control_mask[2] = 0x80;
}

/* Search request list for request with matching sccb. Return request if found,
 * NULL otherwise. Called while sclp_lock is locked. */
static inline struct sclp_req *
__sclp_find_req(u32 sccb)
{
    struct list_head *l;
    struct sclp_req *req;

    list_for_each(l, &sclp_req_queue) {
        req = list_entry(l, struct sclp_req, list);
        if (sccb == (u32) (addr_t) req->sccb)
                return req;
    }
    return NULL;
}

/* Handler for external interruption. Perform request post-processing.
 * Prepare read event data request if necessary. Start processing of next
 * request on queue. */
static void sclp_interrupt_handler(struct ext_code ext_code,
                   unsigned int param32, unsigned long param64)
{
    struct sclp_req *req;
    u32 finished_sccb;
    u32 evbuf_pending;

    kstat_cpu(smp_processor_id()).irqs[EXTINT_SCP]++;
    spin_lock(&sclp_lock);
    finished_sccb = param32 & 0xfffffff8;
    evbuf_pending = param32 & 0x3;
    if (finished_sccb) {
        del_timer(&sclp_request_timer);
        sclp_running_state = sclp_running_state_reset_pending;
        req = __sclp_find_req(finished_sccb);
        if (req) {
            /* Request post-processing */
            list_del(&req->list);
            req->status = SCLP_REQ_DONE;
            if (req->callback) {
                spin_unlock(&sclp_lock);
                req->callback(req, req->callback_data);
                spin_lock(&sclp_lock);
            }
        }
        sclp_running_state = sclp_running_state_idle;
    }
    if (evbuf_pending &&
        sclp_activation_state == sclp_activation_state_active)
        __sclp_queue_read_req();
    spin_unlock(&sclp_lock);
    sclp_process_queue();
}

/* Convert interval in jiffies to TOD ticks. */
static inline u64
sclp_tod_from_jiffies(unsigned long jiffies)
{
    return (u64) (jiffies / HZ) << 32;
}

/* Wait until a currently running request finished. Note: while this function
 * is running, no timers are served on the calling CPU. */
void
sclp_sync_wait(void)
{
    unsigned long long old_tick;
    unsigned long flags;
    unsigned long cr0, cr0_sync;
    u64 timeout;
    int irq_context;

    /* We'll be disabling timer interrupts, so we need a custom timeout
     * mechanism */
    timeout = 0;
    if (timer_pending(&sclp_request_timer)) {
        /* Get timeout TOD value */
        timeout = get_clock() +
              sclp_tod_from_jiffies(sclp_request_timer.expires -
                        jiffies);
    }
    local_irq_save(flags);
    /* Prevent bottom half from executing once we force interrupts open */
    irq_context = in_interrupt();
    if (!irq_context)
        local_bh_disable();
    /* Enable service-signal interruption, disable timer interrupts */
    old_tick = local_tick_disable();
    trace_hardirqs_on();
    __ctl_store(cr0, 0, 0);
    cr0_sync = cr0;
    cr0_sync &= 0xffff00a0;
    cr0_sync |= 0x00000200;
    __ctl_load(cr0_sync, 0, 0);
    __arch_local_irq_stosm(0x01);
    /* Loop until driver state indicates finished request */
    while (sclp_running_state != sclp_running_state_idle) {
        /* Check for expired request timer */
        if (timer_pending(&sclp_request_timer) &&
            get_clock() > timeout &&
            del_timer(&sclp_request_timer))
            sclp_request_timer.function(sclp_request_timer.data);
        cpu_relax();
    }
    local_irq_disable();
    __ctl_load(cr0, 0, 0);
    if (!irq_context)
        _local_bh_enable();
    local_tick_enable(old_tick);
    local_irq_restore(flags);
}
EXPORT_SYMBOL(sclp_sync_wait);

/* Dispatch changes in send and receive mask to registered listeners. */
static void
sclp_dispatch_state_change(void)
{
    struct list_head *l;
    struct sclp_register *reg;
    unsigned long flags;
    sccb_mask_t receive_mask;
    sccb_mask_t send_mask;

    do {
        spin_lock_irqsave(&sclp_lock, flags);
        reg = NULL;
        list_for_each(l, &sclp_reg_list) {
            reg = list_entry(l, struct sclp_register, list);
            receive_mask = reg->send_mask & sclp_receive_mask;
            send_mask = reg->receive_mask & sclp_send_mask;
            if (reg->sclp_receive_mask != receive_mask ||
                reg->sclp_send_mask != send_mask) {
                reg->sclp_receive_mask = receive_mask;
                reg->sclp_send_mask = send_mask;
                break;
            } else
                reg = NULL;
        }
        spin_unlock_irqrestore(&sclp_lock, flags);
        if (reg && reg->state_change_fn)
            reg->state_change_fn(reg);
    } while (reg);
}

struct sclp_statechangebuf {
    struct evbuf_header header;
    u8      validity_sclp_active_facility_mask : 1;
    u8      validity_sclp_receive_mask : 1;
    u8      validity_sclp_send_mask : 1;
    u8      validity_read_data_function_mask : 1;
    u16     _zeros : 12;
    u16     mask_length;
    u64     sclp_active_facility_mask;
    sccb_mask_t sclp_receive_mask;
    sccb_mask_t sclp_send_mask;
    u32     read_data_function_mask;
} __attribute__((packed));


/* State change event callback. Inform listeners of changes. */
static void
sclp_state_change_cb(struct evbuf_header *evbuf)
{
    unsigned long flags;
    struct sclp_statechangebuf *scbuf;

    scbuf = (struct sclp_statechangebuf *) evbuf;
    if (scbuf->mask_length != sizeof(sccb_mask_t))
        return;
    spin_lock_irqsave(&sclp_lock, flags);
    if (scbuf->validity_sclp_receive_mask)
        sclp_receive_mask = scbuf->sclp_receive_mask;
    if (scbuf->validity_sclp_send_mask)
        sclp_send_mask = scbuf->sclp_send_mask;
    spin_unlock_irqrestore(&sclp_lock, flags);
    if (scbuf->validity_sclp_active_facility_mask)
        sclp_facilities = scbuf->sclp_active_facility_mask;
    sclp_dispatch_state_change();
}

static struct sclp_register sclp_state_change_event = {
    .receive_mask = EVTYP_STATECHANGE_MASK,
    .receiver_fn = sclp_state_change_cb
};

/* Calculate receive and send mask of currently registered listeners.
 * Called while sclp_lock is locked. */
static inline void
__sclp_get_mask(sccb_mask_t *receive_mask, sccb_mask_t *send_mask)
{
    struct list_head *l;
    struct sclp_register *t;

    *receive_mask = 0;
    *send_mask = 0;
    list_for_each(l, &sclp_reg_list) {
        t = list_entry(l, struct sclp_register, list);
        *receive_mask |= t->receive_mask;
        *send_mask |= t->send_mask;
    }
}

/* Register event listener. Return 0 on success, non-zero otherwise. */
int
sclp_register(struct sclp_register *reg)
{
    unsigned long flags;
    sccb_mask_t receive_mask;
    sccb_mask_t send_mask;
    int rc;

    rc = sclp_init();
    if (rc)
        return rc;
    spin_lock_irqsave(&sclp_lock, flags);
    /* Check event mask for collisions */
    __sclp_get_mask(&receive_mask, &send_mask);
    if (reg->receive_mask & receive_mask || reg->send_mask & send_mask) {
        spin_unlock_irqrestore(&sclp_lock, flags);
        return -EBUSY;
    }
    /* Trigger initial state change callback */
    reg->sclp_receive_mask = 0;
    reg->sclp_send_mask = 0;
    reg->pm_event_posted = 0;
    list_add(&reg->list, &sclp_reg_list);
    spin_unlock_irqrestore(&sclp_lock, flags);
    rc = sclp_init_mask(1);
    if (rc) {
        spin_lock_irqsave(&sclp_lock, flags);
        list_del(&reg->list);
        spin_unlock_irqrestore(&sclp_lock, flags);
    }
    return rc;
}

EXPORT_SYMBOL(sclp_register);

/* Unregister event listener. */
void
sclp_unregister(struct sclp_register *reg)
{
    unsigned long flags;

    spin_lock_irqsave(&sclp_lock, flags);
    list_del(&reg->list);
    spin_unlock_irqrestore(&sclp_lock, flags);
    sclp_init_mask(1);
}

EXPORT_SYMBOL(sclp_unregister);

/* Remove event buffers which are marked processed. Return the number of
 * remaining event buffers. */
int
sclp_remove_processed(struct sccb_header *sccb)
{
    struct evbuf_header *evbuf;
    int unprocessed;
    u16 remaining;

    evbuf = (struct evbuf_header *) (sccb + 1);
    unprocessed = 0;
    remaining = sccb->length - sizeof(struct sccb_header);
    while (remaining > 0) {
        remaining -= evbuf->length;
        if (evbuf->flags & 0x80) {
            sccb->length -= evbuf->length;
            memcpy(evbuf, (void *) ((addr_t) evbuf + evbuf->length),
                   remaining);
        } else {
            unprocessed++;
            evbuf = (struct evbuf_header *)
                    ((addr_t) evbuf + evbuf->length);
        }
    }
    return unprocessed;
}

EXPORT_SYMBOL(sclp_remove_processed);

/* Prepare init mask request. Called while sclp_lock is locked. */
static inline void
__sclp_make_init_req(u32 receive_mask, u32 send_mask)
{
    struct init_sccb *sccb;

    sccb = (struct init_sccb *) sclp_init_sccb;
    clear_page(sccb);
    memset(&sclp_init_req, 0, sizeof(struct sclp_req));
    sclp_init_req.command = SCLP_CMDW_WRITE_EVENT_MASK;
    sclp_init_req.status = SCLP_REQ_FILLED;
    sclp_init_req.start_count = 0;
    sclp_init_req.callback = NULL;
    sclp_init_req.callback_data = NULL;
    sclp_init_req.sccb = sccb;
    sccb->header.length = sizeof(struct init_sccb);
    sccb->mask_length = sizeof(sccb_mask_t);
    sccb->receive_mask = receive_mask;
    sccb->send_mask = send_mask;
    sccb->sclp_receive_mask = 0;
    sccb->sclp_send_mask = 0;
}

/* Start init mask request. If calculate is non-zero, calculate the mask as
 * requested by registered listeners. Use zero mask otherwise. Return 0 on
 * success, non-zero otherwise. */
static int
sclp_init_mask(int calculate)
{
    unsigned long flags;
    struct init_sccb *sccb = (struct init_sccb *) sclp_init_sccb;
    sccb_mask_t receive_mask;
    sccb_mask_t send_mask;
    int retry;
    int rc;
    unsigned long wait;

    spin_lock_irqsave(&sclp_lock, flags);
    /* Check if interface is in appropriate state */
    if (sclp_mask_state != sclp_mask_state_idle) {
        spin_unlock_irqrestore(&sclp_lock, flags);
        return -EBUSY;
    }
    if (sclp_activation_state == sclp_activation_state_inactive) {
        spin_unlock_irqrestore(&sclp_lock, flags);
        return -EINVAL;
    }
    sclp_mask_state = sclp_mask_state_initializing;
    /* Determine mask */
    if (calculate)
        __sclp_get_mask(&receive_mask, &send_mask);
    else {
        receive_mask = 0;
        send_mask = 0;
    }
    rc = -EIO;
    for (retry = 0; retry <= SCLP_MASK_RETRY; retry++) {
        /* Prepare request */
        __sclp_make_init_req(receive_mask, send_mask);
        spin_unlock_irqrestore(&sclp_lock, flags);
        if (sclp_add_request(&sclp_init_req)) {
            /* Try again later */
            wait = jiffies + SCLP_BUSY_INTERVAL * HZ;
            while (time_before(jiffies, wait))
                sclp_sync_wait();
            spin_lock_irqsave(&sclp_lock, flags);
            continue;
        }
        while (sclp_init_req.status != SCLP_REQ_DONE &&
               sclp_init_req.status != SCLP_REQ_FAILED)
            sclp_sync_wait();
        spin_lock_irqsave(&sclp_lock, flags);
        if (sclp_init_req.status == SCLP_REQ_DONE &&
            sccb->header.response_code == 0x20) {
            /* Successful request */
            if (calculate) {
                sclp_receive_mask = sccb->sclp_receive_mask;
                sclp_send_mask = sccb->sclp_send_mask;
            } else {
                sclp_receive_mask = 0;
                sclp_send_mask = 0;
            }
            spin_unlock_irqrestore(&sclp_lock, flags);
            sclp_dispatch_state_change();
            spin_lock_irqsave(&sclp_lock, flags);
            rc = 0;
            break;
        }
    }
    sclp_mask_state = sclp_mask_state_idle;
    spin_unlock_irqrestore(&sclp_lock, flags);
    return rc;
}

/* Deactivate SCLP interface. On success, new requests will be rejected,
 * events will no longer be dispatched. Return 0 on success, non-zero
 * otherwise. */
int
sclp_deactivate(void)
{
    unsigned long flags;
    int rc;

    spin_lock_irqsave(&sclp_lock, flags);
    /* Deactivate can only be called when active */
    if (sclp_activation_state != sclp_activation_state_active) {
        spin_unlock_irqrestore(&sclp_lock, flags);
        return -EINVAL;
    }
    sclp_activation_state = sclp_activation_state_deactivating;
    spin_unlock_irqrestore(&sclp_lock, flags);
    rc = sclp_init_mask(0);
    spin_lock_irqsave(&sclp_lock, flags);
    if (rc == 0)
        sclp_activation_state = sclp_activation_state_inactive;
    else
        sclp_activation_state = sclp_activation_state_active;
    spin_unlock_irqrestore(&sclp_lock, flags);
    return rc;
}

EXPORT_SYMBOL(sclp_deactivate);

/* Reactivate SCLP interface after sclp_deactivate. On success, new
 * requests will be accepted, events will be dispatched again. Return 0 on
 * success, non-zero otherwise. */
int
sclp_reactivate(void)
{
    unsigned long flags;
    int rc;

    spin_lock_irqsave(&sclp_lock, flags);
    /* Reactivate can only be called when inactive */
    if (sclp_activation_state != sclp_activation_state_inactive) {
        spin_unlock_irqrestore(&sclp_lock, flags);
        return -EINVAL;
    }
    sclp_activation_state = sclp_activation_state_activating;
    spin_unlock_irqrestore(&sclp_lock, flags);
    rc = sclp_init_mask(1);
    spin_lock_irqsave(&sclp_lock, flags);
    if (rc == 0)
        sclp_activation_state = sclp_activation_state_active;
    else
        sclp_activation_state = sclp_activation_state_inactive;
    spin_unlock_irqrestore(&sclp_lock, flags);
    return rc;
}

EXPORT_SYMBOL(sclp_reactivate);

/* Handler for external interruption used during initialization. Modify
 * request state to done. */
static void sclp_check_handler(struct ext_code ext_code,
                   unsigned int param32, unsigned long param64)
{
    u32 finished_sccb;

    kstat_cpu(smp_processor_id()).irqs[EXTINT_SCP]++;
    finished_sccb = param32 & 0xfffffff8;
    /* Is this the interrupt we are waiting for? */
    if (finished_sccb == 0)
        return;
    if (finished_sccb != (u32) (addr_t) sclp_init_sccb)
        panic("sclp: unsolicited interrupt for buffer at 0x%x\n",
              finished_sccb);
    spin_lock(&sclp_lock);
    if (sclp_running_state == sclp_running_state_running) {
        sclp_init_req.status = SCLP_REQ_DONE;
        sclp_running_state = sclp_running_state_idle;
    }
    spin_unlock(&sclp_lock);
}

/* Initial init mask request timed out. Modify request state to failed. */
static void
sclp_check_timeout(unsigned long data)
{
    unsigned long flags;

    spin_lock_irqsave(&sclp_lock, flags);
    if (sclp_running_state == sclp_running_state_running) {
        sclp_init_req.status = SCLP_REQ_FAILED;
        sclp_running_state = sclp_running_state_idle;
    }
    spin_unlock_irqrestore(&sclp_lock, flags);
}

/* Perform a check of the SCLP interface. Return zero if the interface is
 * available and there are no pending requests from a previous instance.
 * Return non-zero otherwise. */
static int
sclp_check_interface(void)
{
    struct init_sccb *sccb;
    unsigned long flags;
    int retry;
    int rc;

    spin_lock_irqsave(&sclp_lock, flags);
    /* Prepare init mask command */
    rc = register_external_interrupt(0x2401, sclp_check_handler);
    if (rc) {
        spin_unlock_irqrestore(&sclp_lock, flags);
        return rc;
    }
    for (retry = 0; retry <= SCLP_INIT_RETRY; retry++) {
        __sclp_make_init_req(0, 0);
        sccb = (struct init_sccb *) sclp_init_req.sccb;
        rc = sclp_service_call(sclp_init_req.command, sccb);
        if (rc == -EIO)
            break;
        sclp_init_req.status = SCLP_REQ_RUNNING;
        sclp_running_state = sclp_running_state_running;
        __sclp_set_request_timer(SCLP_RETRY_INTERVAL * HZ,
                     sclp_check_timeout, 0);
        spin_unlock_irqrestore(&sclp_lock, flags);
        /* Enable service-signal interruption - needs to happen
         * with IRQs enabled. */
        service_subclass_irq_register();
        /* Wait for signal from interrupt or timeout */
        sclp_sync_wait();
        /* Disable service-signal interruption - needs to happen
         * with IRQs enabled. */
        service_subclass_irq_unregister();
        spin_lock_irqsave(&sclp_lock, flags);
        del_timer(&sclp_request_timer);
        if (sclp_init_req.status == SCLP_REQ_DONE &&
            sccb->header.response_code == 0x20) {
            rc = 0;
            break;
        } else
            rc = -EBUSY;
    }
    unregister_external_interrupt(0x2401, sclp_check_handler);
    spin_unlock_irqrestore(&sclp_lock, flags);
    return rc;
}

/* Reboot event handler. Reset send and receive mask to prevent pending SCLP
 * events from interfering with rebooted system. */
static int
sclp_reboot_event(struct notifier_block *this, unsigned long event, void *ptr)
{
    sclp_deactivate();
    return NOTIFY_DONE;
}

static struct notifier_block sclp_reboot_notifier = {
    .notifier_call = sclp_reboot_event
};

/*
 * Suspend/resume SCLP notifier implementation
 */

static void sclp_pm_event(enum sclp_pm_event sclp_pm_event, int rollback)
{
    struct sclp_register *reg;
    unsigned long flags;

    if (!rollback) {
        spin_lock_irqsave(&sclp_lock, flags);
        list_for_each_entry(reg, &sclp_reg_list, list)
            reg->pm_event_posted = 0;
        spin_unlock_irqrestore(&sclp_lock, flags);
    }
    do {
        spin_lock_irqsave(&sclp_lock, flags);
        list_for_each_entry(reg, &sclp_reg_list, list) {
            if (rollback && reg->pm_event_posted)
                goto found;
            if (!rollback && !reg->pm_event_posted)
                goto found;
        }
        spin_unlock_irqrestore(&sclp_lock, flags);
        return;
found:
        spin_unlock_irqrestore(&sclp_lock, flags);
        if (reg->pm_event_fn)
            reg->pm_event_fn(reg, sclp_pm_event);
        reg->pm_event_posted = rollback ? 0 : 1;
    } while (1);
}

/*
 * Susend/resume callbacks for platform device
 */

static int sclp_freeze(struct device *dev)
{
    unsigned long flags;
    int rc;

    sclp_pm_event(SCLP_PM_EVENT_FREEZE, 0);

    spin_lock_irqsave(&sclp_lock, flags);
    sclp_suspend_state = sclp_suspend_state_suspended;
    spin_unlock_irqrestore(&sclp_lock, flags);

    /* Init supend data */
    memset(&sclp_suspend_req, 0, sizeof(sclp_suspend_req));
    sclp_suspend_req.callback = sclp_suspend_req_cb;
    sclp_suspend_req.status = SCLP_REQ_FILLED;
    init_completion(&sclp_request_queue_flushed);

    rc = sclp_add_request(&sclp_suspend_req);
    if (rc == 0)
        wait_for_completion(&sclp_request_queue_flushed);
    else if (rc != -ENODATA)
        goto fail_thaw;

    rc = sclp_deactivate();
    if (rc)
        goto fail_thaw;
    return 0;

fail_thaw:
    spin_lock_irqsave(&sclp_lock, flags);
    sclp_suspend_state = sclp_suspend_state_running;
    spin_unlock_irqrestore(&sclp_lock, flags);
    sclp_pm_event(SCLP_PM_EVENT_THAW, 1);
    return rc;
}

static int sclp_undo_suspend(enum sclp_pm_event event)
{
    unsigned long flags;
    int rc;

    rc = sclp_reactivate();
    if (rc)
        return rc;

    spin_lock_irqsave(&sclp_lock, flags);
    sclp_suspend_state = sclp_suspend_state_running;
    spin_unlock_irqrestore(&sclp_lock, flags);

    sclp_pm_event(event, 0);
    return 0;
}

static int sclp_thaw(struct device *dev)
{
    return sclp_undo_suspend(SCLP_PM_EVENT_THAW);
}

static int sclp_restore(struct device *dev)
{
    return sclp_undo_suspend(SCLP_PM_EVENT_RESTORE);
}

static const struct dev_pm_ops sclp_pm_ops = {
    .freeze     = sclp_freeze,
    .thaw       = sclp_thaw,
    .restore    = sclp_restore,
};

static struct platform_driver sclp_pdrv = {
    .driver = {
        .name   = "sclp",
        .owner  = THIS_MODULE,
        .pm = &sclp_pm_ops,
    },
};

static struct platform_device *sclp_pdev;

/* Initialize SCLP driver. Return zero if driver is operational, non-zero
 * otherwise. */
static int
sclp_init(void)
{
    unsigned long flags;
    int rc = 0;

    spin_lock_irqsave(&sclp_lock, flags);
    /* Check for previous or running initialization */
    if (sclp_init_state != sclp_init_state_uninitialized)
        goto fail_unlock;
    sclp_init_state = sclp_init_state_initializing;
    /* Set up variables */
    INIT_LIST_HEAD(&sclp_req_queue);
    INIT_LIST_HEAD(&sclp_reg_list);
    list_add(&sclp_state_change_event.list, &sclp_reg_list);
    init_timer(&sclp_request_timer);
    /* Check interface */
    spin_unlock_irqrestore(&sclp_lock, flags);
    rc = sclp_check_interface();
    spin_lock_irqsave(&sclp_lock, flags);
    if (rc)
        goto fail_init_state_uninitialized;
    /* Register reboot handler */
    rc = register_reboot_notifier(&sclp_reboot_notifier);
    if (rc)
        goto fail_init_state_uninitialized;
    /* Register interrupt handler */
    rc = register_external_interrupt(0x2401, sclp_interrupt_handler);
    if (rc)
        goto fail_unregister_reboot_notifier;
    sclp_init_state = sclp_init_state_initialized;
    spin_unlock_irqrestore(&sclp_lock, flags);
    /* Enable service-signal external interruption - needs to happen with
     * IRQs enabled. */
    service_subclass_irq_register();
    sclp_init_mask(1);
    return 0;

fail_unregister_reboot_notifier:
    unregister_reboot_notifier(&sclp_reboot_notifier);
fail_init_state_uninitialized:
    sclp_init_state = sclp_init_state_uninitialized;
fail_unlock:
    spin_unlock_irqrestore(&sclp_lock, flags);
    return rc;
}

/*
 * SCLP panic notifier: If we are suspended, we thaw SCLP in order to be able
 * to print the panic message.
 */
static int sclp_panic_notify(struct notifier_block *self,
                 unsigned long event, void *data)
{
    if (sclp_suspend_state == sclp_suspend_state_suspended)
        sclp_undo_suspend(SCLP_PM_EVENT_THAW);
    return NOTIFY_OK;
}

static struct notifier_block sclp_on_panic_nb = {
    .notifier_call = sclp_panic_notify,
    .priority = SCLP_PANIC_PRIO,
};

static __init int sclp_initcall(void)
{
    int rc;

    rc = platform_driver_register(&sclp_pdrv);
    if (rc)
        return rc;
    sclp_pdev = platform_device_register_simple("sclp", -1, NULL, 0);
    rc = IS_ERR(sclp_pdev) ? PTR_ERR(sclp_pdev) : 0;
    if (rc)
        goto fail_platform_driver_unregister;
    rc = atomic_notifier_chain_register(&panic_notifier_list,
                        &sclp_on_panic_nb);
    if (rc)
        goto fail_platform_device_unregister;

    return sclp_init();

fail_platform_device_unregister:
    platform_device_unregister(sclp_pdev);
fail_platform_driver_unregister:
    platform_driver_unregister(&sclp_pdrv);
    return rc;
}

arch_initcall(sclp_initcall);