// SPDX-License-Identifier: GPL-2.0
/*
 *   Channel report handling code
 *
 *    Copyright IBM Corp. 2000, 2009
 *    Author(s): Ingo Adlung <adlung@de.ibm.com>,
 *               Martin Schwidefsky <schwidefsky@de.ibm.com>,
 *               Cornelia Huck <cornelia.huck@de.ibm.com>,
 */

#include <linux/mutex.h>
#include <linux/kthread.h>
#include <linux/init.h>
#include <linux/wait.h>
#include <asm/ctlreg.h>
#include <asm/crw.h>
#include "ioasm.h"

static DEFINE_MUTEX(crw_handler_mutex);
static crw_handler_t crw_handlers[NR_RSCS];
static atomic_t crw_nr_req = ATOMIC_INIT(0);
static DECLARE_WAIT_QUEUE_HEAD(crw_handler_wait_q);

/**
 * crw_register_handler() - register a channel report word handler
 * @rsc: reporting source code to handle
 * @handler: handler to be registered
 *
 * Returns %0 on success and a negative error value otherwise.
 */
int crw_register_handler(int rsc, crw_handler_t handler)
{
        int rc = 0;

        if ((rsc < 0) || (rsc >= NR_RSCS))
                return -EINVAL;
        mutex_lock(&crw_handler_mutex);
        if (crw_handlers[rsc])
                rc = -EBUSY;
        else
                crw_handlers[rsc] = handler;
        mutex_unlock(&crw_handler_mutex);
        return rc;
}

/**
 * crw_unregister_handler() - unregister a channel report word handler
 * @rsc: reporting source code to handle
 */
void crw_unregister_handler(int rsc)
{
        if ((rsc < 0) || (rsc >= NR_RSCS))
                return;
        mutex_lock(&crw_handler_mutex);
        crw_handlers[rsc] = NULL;
        mutex_unlock(&crw_handler_mutex);
}

/*
 * Retrieve CRWs and call function to handle event.
 */
static int crw_collect_info(void *unused)
{
        struct crw crw[2];
        int ccode, signal;
        unsigned int chain;

repeat:
        signal = wait_event_interruptible(crw_handler_wait_q,
                                          atomic_read(&crw_nr_req) > 0);
        if (unlikely(signal))
                atomic_inc(&crw_nr_req);
        chain = 0;
        while (1) {
                crw_handler_t handler;

                if (unlikely(chain > 1)) {
                        struct crw tmp_crw;

                        printk(KERN_WARNING "%s: Code does not support more than two chained crws\n",
                               __func__);
                        ccode = stcrw(&tmp_crw);
                        printk(KERN_WARNING"%s: crw reports slct=%d, oflw=%d, "
                               "chn=%d, rsc=%X, anc=%d, erc=%X, rsid=%X\n",
                               __func__, tmp_crw.slct, tmp_crw.oflw,
                               tmp_crw.chn, tmp_crw.rsc, tmp_crw.anc,
                               tmp_crw.erc, tmp_crw.rsid);
                        printk(KERN_WARNING"%s: This was crw number %x in the "
                               "chain\n", __func__, chain);
                        if (ccode != 0)
                                break;
                        chain = tmp_crw.chn ? chain + 1 : 0;
                        continue;
                }
                ccode = stcrw(&crw[chain]);
                if (ccode != 0)
                        break;
                printk(KERN_DEBUG "crw_info : CRW reports slct=%d, oflw=%d, "
                       "chn=%d, rsc=%X, anc=%d, erc=%X, rsid=%X\n",
                       crw[chain].slct, crw[chain].oflw, crw[chain].chn,
                       crw[chain].rsc, crw[chain].anc, crw[chain].erc,
                       crw[chain].rsid);
                /* Check for overflows. */
                if (crw[chain].oflw) {
                        int i;

                        pr_debug("%s: crw overflow detected!\n", __func__);
                        mutex_lock(&crw_handler_mutex);
                        for (i = 0; i < NR_RSCS; i++) {
                                if (crw_handlers[i])
                                        crw_handlers[i](NULL, NULL, 1);
                        }
                        mutex_unlock(&crw_handler_mutex);
                        chain = 0;
                        continue;
                }
                if (crw[0].chn && !chain) {
                        chain++;
                        continue;
                }
                mutex_lock(&crw_handler_mutex);
                handler = crw_handlers[crw[chain].rsc];
                if (handler)
                        handler(&crw[0], chain ? &crw[1] : NULL, 0);
                mutex_unlock(&crw_handler_mutex);
                /* chain is always 0 or 1 here. */
                chain = crw[chain].chn ? chain + 1 : 0;
        }
        if (atomic_dec_and_test(&crw_nr_req))
                wake_up(&crw_handler_wait_q);
        goto repeat;
        return 0;
}

void crw_handle_channel_report(void)
{
        atomic_inc(&crw_nr_req);
        wake_up(&crw_handler_wait_q);
}

void crw_wait_for_channel_report(void)
{
        crw_handle_channel_report();
        wait_event(crw_handler_wait_q, atomic_read(&crw_nr_req) == 0);
}

/*
 * Machine checks for the channel subsystem must be enabled
 * after the channel subsystem is initialized
 */
static int __init crw_machine_check_init(void)
{
        struct task_struct *task;

        task = kthread_run(crw_collect_info, NULL, "kmcheck");
        if (IS_ERR(task))
                return PTR_ERR(task);
        system_ctl_set_bit(14, CR14_CHANNEL_REPORT_SUBMASK_BIT);
        return 0;
}
device_initcall(crw_machine_check_init);