// SPDX-License-Identifier: GPL-2.0
/*
 * core function to access sclp interface
 *
 * Copyright IBM Corp. 1999, 2009
 *
 * Author(s): Martin Peschke <mpeschke@de.ibm.com>
 *            Martin Schwidefsky <schwidefsky@de.ibm.com>
 */

#include <linux/kernel_stat.h>
#include <linux/module.h>
#include <linux/err.h>
#include <linux/panic_notifier.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/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 LIST_HEAD(sclp_reg_list);

/* List of queued requests. */
static 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 void *sclp_read_sccb;
static struct init_sccb *sclp_init_sccb;

/* Number of console pages to allocate, used by sclp_con.c and sclp_vt220.c */
int sclp_console_pages = SCLP_CONSOLE_PAGES;
/* Flag to indicate if buffer pages are dropped on buffer full condition */
int sclp_console_drop = 1;
/* Number of times the console dropped buffer pages */
unsigned long sclp_console_full;

static int __init sclp_setup_console_pages(char *str)
{
        int pages, rc;

        rc = kstrtoint(str, 0, &pages);
        if (!rc && pages >= SCLP_CONSOLE_PAGES)
                sclp_console_pages = pages;
        return 1;
}

__setup("sclp_con_pages=", sclp_setup_console_pages);

static int __init sclp_setup_console_drop(char *str)
{
        int drop, rc;

        rc = kstrtoint(str, 0, &drop);
        if (!rc)
                sclp_console_drop = drop;
        return 1;
}

__setup("sclp_con_drop=", sclp_setup_console_drop);

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

/* Timer for queued requests. */
static struct timer_list sclp_queue_timer;

/* 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;

/* 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_request_timeout(bool force_restart);
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);

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 (*cb)(struct timer_list *))
{
        del_timer(&sclp_request_timer);
        sclp_request_timer.function = cb;
        sclp_request_timer.expires = jiffies + time;
        add_timer(&sclp_request_timer);
}

static void sclp_request_timeout_restart(struct timer_list *unused)
{
        sclp_request_timeout(true);
}

static void sclp_request_timeout_normal(struct timer_list *unused)
{
        sclp_request_timeout(false);
}

/* Request timeout handler. Restart the request queue. If force_restart,
 * force restart of running request. */
static void sclp_request_timeout(bool force_restart)
{
        unsigned long flags;

        spin_lock_irqsave(&sclp_lock, flags);
        if (force_restart) {
                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_normal);
        }
        spin_unlock_irqrestore(&sclp_lock, flags);
        sclp_process_queue();
}

/*
 * Returns the expire value in jiffies of the next pending request timeout,
 * if any. Needs to be called with sclp_lock.
 */
static unsigned long __sclp_req_queue_find_next_timeout(void)
{
        unsigned long expires_next = 0;
        struct sclp_req *req;

        list_for_each_entry(req, &sclp_req_queue, list) {
                if (!req->queue_expires)
                        continue;
                if (!expires_next ||
                   (time_before(req->queue_expires, expires_next)))
                                expires_next = req->queue_expires;
        }
        return expires_next;
}

/*
 * Returns expired request, if any, and removes it from the list.
 */
static struct sclp_req *__sclp_req_queue_remove_expired_req(void)
{
        unsigned long flags, now;
        struct sclp_req *req;

        spin_lock_irqsave(&sclp_lock, flags);
        now = jiffies;
        /* Don't need list_for_each_safe because we break out after list_del */
        list_for_each_entry(req, &sclp_req_queue, list) {
                if (!req->queue_expires)
                        continue;
                if (time_before_eq(req->queue_expires, now)) {
                        if (req->status == SCLP_REQ_QUEUED) {
                                req->status = SCLP_REQ_QUEUED_TIMEOUT;
                                list_del(&req->list);
                                goto out;
                        }
                }
        }
        req = NULL;
out:
        spin_unlock_irqrestore(&sclp_lock, flags);
        return req;
}

/*
 * Timeout handler for queued requests. Removes request from list and
 * invokes callback. This timer can be set per request in situations where
 * waiting too long would be harmful to the system, e.g. during SE reboot.
 */
static void sclp_req_queue_timeout(struct timer_list *unused)
{
        unsigned long flags, expires_next;
        struct sclp_req *req;

        do {
                req = __sclp_req_queue_remove_expired_req();
                if (req && req->callback)
                        req->callback(req, req->callback_data);
        } while (req);

        spin_lock_irqsave(&sclp_lock, flags);
        expires_next = __sclp_req_queue_find_next_timeout();
        if (expires_next)
                mod_timer(&sclp_queue_timer, expires_next);
        spin_unlock_irqrestore(&sclp_lock, flags);
}

/* 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_restart);
                return 0;
        } else if (rc == -EBUSY) {
                /* Try again later */
                __sclp_set_request_timer(SCLP_BUSY_INTERVAL * HZ,
                                         sclp_request_timeout_normal);
                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);
                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_normal);
                        break;
                }
                /* 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_init_req)
                return 1;
        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;
        if (req->queue_timeout) {
                req->queue_expires = jiffies + req->queue_timeout * HZ;
                if (!timer_pending(&sclp_queue_timer) ||
                    time_after(sclp_queue_timer.expires, req->queue_expires))
                        mod_timer(&sclp_queue_timer, req->queue_expires);
        } else
                req->queue_expires = 0;
        /* Start if request is first in list */
        if (sclp_running_state == sclp_running_state_idle &&
            req->list.prev == &sclp_req_queue) {
                rc = __sclp_start_request(req);
                if (rc)
                        list_del(&req->list);
        }
        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 & SCLP_EVTYP_MASK(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;

        inc_irq_stat(IRQEXT_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_tod_clock_fast() +
                          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_IRQ_SUBCLASS_MASK;
        cr0_sync |= 1UL << (63 - 54);
        __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_tod_clock_fast() > timeout &&
                    del_timer(&sclp_request_timer))
                        sclp_request_timer.function(&sclp_request_timer);
                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;
        u8              masks[2 * 1021 + 4];    /* variable length */
        /*
         * u8           sclp_receive_mask[mask_length];
         * u8           sclp_send_mask[mask_length];
         * 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;

        BUILD_BUG_ON(sizeof(struct sclp_statechangebuf) > PAGE_SIZE);

        scbuf = (struct sclp_statechangebuf *) evbuf;
        spin_lock_irqsave(&sclp_lock, flags);
        if (scbuf->validity_sclp_receive_mask)
                sclp_receive_mask = sccb_get_recv_mask(scbuf);
        if (scbuf->validity_sclp_send_mask)
                sclp_send_mask = sccb_get_send_mask(scbuf);
        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;
        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(sccb_mask_t receive_mask, sccb_mask_t send_mask)
{
        struct init_sccb *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(*sccb);
        if (sclp_mask_compat_mode)
                sccb->mask_length = SCLP_MASK_SIZE_COMPAT;
        else
                sccb->mask_length = sizeof(sccb_mask_t);
        sccb_set_recv_mask(sccb, receive_mask);
        sccb_set_send_mask(sccb, send_mask);
        sccb_set_sclp_recv_mask(sccb, 0);
        sccb_set_sclp_send_mask(sccb, 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 = 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_get_sclp_recv_mask(sccb);
                                sclp_send_mask = sccb_get_sclp_send_mask(sccb);
                        } 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;

        inc_irq_stat(IRQEXT_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(struct timer_list *unused)
{
        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_irq(EXT_IRQ_SERVICE_SIG, 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);
                spin_unlock_irqrestore(&sclp_lock, flags);
                /* Enable service-signal interruption - needs to happen
                 * with IRQs enabled. */
                irq_subclass_register(IRQ_SUBCLASS_SERVICE_SIGNAL);
                /* Wait for signal from interrupt or timeout */
                sclp_sync_wait();
                /* Disable service-signal interruption - needs to happen
                 * with IRQs enabled. */
                irq_subclass_unregister(IRQ_SUBCLASS_SERVICE_SIGNAL);
                spin_lock_irqsave(&sclp_lock, flags);
                del_timer(&sclp_request_timer);
                rc = -EBUSY;
                if (sclp_init_req.status == SCLP_REQ_DONE) {
                        if (sccb->header.response_code == 0x20) {
                                rc = 0;
                                break;
                        } else if (sccb->header.response_code == 0x74f0) {
                                if (!sclp_mask_compat_mode) {
                                        sclp_mask_compat_mode = true;
                                        retry = 0;
                                }
                        }
                }
        }
        unregister_external_irq(EXT_IRQ_SERVICE_SIG, 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
};

static ssize_t con_pages_show(struct device_driver *dev, char *buf)
{
        return sprintf(buf, "%i\n", sclp_console_pages);
}

static DRIVER_ATTR_RO(con_pages);

static ssize_t con_drop_show(struct device_driver *dev, char *buf)
{
        return sprintf(buf, "%i\n", sclp_console_drop);
}

static DRIVER_ATTR_RO(con_drop);

static ssize_t con_full_show(struct device_driver *dev, char *buf)
{
        return sprintf(buf, "%lu\n", sclp_console_full);

}

static DRIVER_ATTR_RO(con_full);

static struct attribute *sclp_drv_attrs[] = {
        &driver_attr_con_pages.attr,
        &driver_attr_con_drop.attr,
        &driver_attr_con_full.attr,
        NULL,
};
static struct attribute_group sclp_drv_attr_group = {
        .attrs = sclp_drv_attrs,
};
static const struct attribute_group *sclp_drv_attr_groups[] = {
        &sclp_drv_attr_group,
        NULL,
};

static struct platform_driver sclp_pdrv = {
        .driver = {
                .name   = "sclp",
                .groups = sclp_drv_attr_groups,
        },
};

/* 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;
        sclp_read_sccb = (void *) __get_free_page(GFP_ATOMIC | GFP_DMA);
        sclp_init_sccb = (void *) __get_free_page(GFP_ATOMIC | GFP_DMA);
        BUG_ON(!sclp_read_sccb || !sclp_init_sccb);
        /* Set up variables */
        list_add(&sclp_state_change_event.list, &sclp_reg_list);
        timer_setup(&sclp_request_timer, NULL, 0);
        timer_setup(&sclp_queue_timer, sclp_req_queue_timeout, 0);
        /* 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_irq(EXT_IRQ_SERVICE_SIG, 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. */
        irq_subclass_register(IRQ_SUBCLASS_SERVICE_SIGNAL);
        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;
        free_page((unsigned long) sclp_read_sccb);
        free_page((unsigned long) sclp_init_sccb);
fail_unlock:
        spin_unlock_irqrestore(&sclp_lock, flags);
        return rc;
}

static __init int sclp_initcall(void)
{
        int rc;

        rc = platform_driver_register(&sclp_pdrv);
        if (rc)
                return rc;

        return sclp_init();
}

arch_initcall(sclp_initcall);