// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright IBM Corp. 2000, 2009
 * Author(s): Utz Bacher <utz.bacher@de.ibm.com>
 *            Cornelia Huck <cornelia.huck@de.ibm.com>
 *            Jan Glauber <jang@linux.vnet.ibm.com>
 */
#include <linux/io.h>
#include <linux/slab.h>
#include <linux/kernel_stat.h>
#include <linux/atomic.h>
#include <linux/rculist.h>

#include <asm/debug.h>
#include <asm/qdio.h>
#include <asm/airq.h>
#include <asm/isc.h>

#include "cio.h"
#include "ioasm.h"
#include "qdio.h"
#include "qdio_debug.h"

/*
 * Restriction: only 63 iqdio subchannels would have its own indicator,
 * after that, subsequent subchannels share one indicator
 */
#define TIQDIO_NR_NONSHARED_IND         63
#define TIQDIO_NR_INDICATORS            (TIQDIO_NR_NONSHARED_IND + 1)
#define TIQDIO_SHARED_IND               63

/* device state change indicators */
struct indicator_t {
        u32 ind;        /* u32 because of compare-and-swap performance */
        atomic_t count; /* use count, 0 or 1 for non-shared indicators */
};

/* list of thin interrupt input queues */
static LIST_HEAD(tiq_list);
static DEFINE_MUTEX(tiq_list_lock);

static struct indicator_t *q_indicators;

u64 last_ai_time;

/* returns addr for the device state change indicator */
static u32 *get_indicator(void)
{
        int i;

        for (i = 0; i < TIQDIO_NR_NONSHARED_IND; i++)
                if (!atomic_cmpxchg(&q_indicators[i].count, 0, 1))
                        return &q_indicators[i].ind;

        /* use the shared indicator */
        atomic_inc(&q_indicators[TIQDIO_SHARED_IND].count);
        return &q_indicators[TIQDIO_SHARED_IND].ind;
}

static void put_indicator(u32 *addr)
{
        struct indicator_t *ind = container_of(addr, struct indicator_t, ind);

        if (!addr)
                return;
        atomic_dec(&ind->count);
}

void tiqdio_add_device(struct qdio_irq *irq_ptr)
{
        mutex_lock(&tiq_list_lock);
        list_add_rcu(&irq_ptr->entry, &tiq_list);
        mutex_unlock(&tiq_list_lock);
}

void tiqdio_remove_device(struct qdio_irq *irq_ptr)
{
        mutex_lock(&tiq_list_lock);
        list_del_rcu(&irq_ptr->entry);
        mutex_unlock(&tiq_list_lock);
        synchronize_rcu();
        INIT_LIST_HEAD(&irq_ptr->entry);
}

static inline int references_shared_dsci(struct qdio_irq *irq_ptr)
{
        return irq_ptr->dsci == &q_indicators[TIQDIO_SHARED_IND].ind;
}

int test_nonshared_ind(struct qdio_irq *irq_ptr)
{
        if (!is_thinint_irq(irq_ptr))
                return 0;
        if (references_shared_dsci(irq_ptr))
                return 0;
        if (*irq_ptr->dsci)
                return 1;
        else
                return 0;
}

static inline u32 clear_shared_ind(void)
{
        if (!atomic_read(&q_indicators[TIQDIO_SHARED_IND].count))
                return 0;
        return xchg(&q_indicators[TIQDIO_SHARED_IND].ind, 0);
}

static inline void tiqdio_call_inq_handlers(struct qdio_irq *irq)
{
        struct qdio_q *q;
        int i;

        if (!references_shared_dsci(irq))
                xchg(irq->dsci, 0);

        if (irq->irq_poll) {
                if (!test_and_set_bit(QDIO_IRQ_DISABLED, &irq->poll_state))
                        irq->irq_poll(irq->cdev, irq->int_parm);
                else
                        QDIO_PERF_STAT_INC(irq, int_discarded);

                return;
        }

        for_each_input_queue(irq, q, i) {
                /*
                 * Call inbound processing but not directly
                 * since that could starve other thinint queues.
                 */
                tasklet_schedule(&q->tasklet);
        }
}

/**
 * tiqdio_thinint_handler - thin interrupt handler for qdio
 * @airq: pointer to adapter interrupt descriptor
 * @floating: flag to recognize floating vs. directed interrupts (unused)
 */
static void tiqdio_thinint_handler(struct airq_struct *airq, bool floating)
{
        u32 si_used = clear_shared_ind();
        struct qdio_irq *irq;

        last_ai_time = S390_lowcore.int_clock;
        inc_irq_stat(IRQIO_QAI);

        /* protect tiq_list entries, only changed in activate or shutdown */
        rcu_read_lock();

        list_for_each_entry_rcu(irq, &tiq_list, entry) {
                /* only process queues from changed sets */
                if (unlikely(references_shared_dsci(irq))) {
                        if (!si_used)
                                continue;
                } else if (!*irq->dsci)
                        continue;

                tiqdio_call_inq_handlers(irq);

                QDIO_PERF_STAT_INC(irq, adapter_int);
        }
        rcu_read_unlock();
}

static struct airq_struct tiqdio_airq = {
        .handler = tiqdio_thinint_handler,
        .isc = QDIO_AIRQ_ISC,
};

static int set_subchannel_ind(struct qdio_irq *irq_ptr, int reset)
{
        struct chsc_scssc_area *scssc = (void *)irq_ptr->chsc_page;
        u64 summary_indicator_addr, subchannel_indicator_addr;
        int rc;

        if (reset) {
                summary_indicator_addr = 0;
                subchannel_indicator_addr = 0;
        } else {
                summary_indicator_addr = virt_to_phys(tiqdio_airq.lsi_ptr);
                subchannel_indicator_addr = virt_to_phys(irq_ptr->dsci);
        }

        rc = chsc_sadc(irq_ptr->schid, scssc, summary_indicator_addr,
                       subchannel_indicator_addr, tiqdio_airq.isc);
        if (rc) {
                DBF_ERROR("%4x SSI r:%4x", irq_ptr->schid.sch_no,
                          scssc->response.code);
                goto out;
        }

        DBF_EVENT("setscind");
        DBF_HEX(&summary_indicator_addr, sizeof(summary_indicator_addr));
        DBF_HEX(&subchannel_indicator_addr, sizeof(subchannel_indicator_addr));
out:
        return rc;
}

int qdio_establish_thinint(struct qdio_irq *irq_ptr)
{
        int rc;

        if (!is_thinint_irq(irq_ptr))
                return 0;

        irq_ptr->dsci = get_indicator();
        DBF_HEX(&irq_ptr->dsci, sizeof(void *));

        rc = set_subchannel_ind(irq_ptr, 0);
        if (rc)
                put_indicator(irq_ptr->dsci);

        return rc;
}

void qdio_shutdown_thinint(struct qdio_irq *irq_ptr)
{
        if (!is_thinint_irq(irq_ptr))
                return;

        /* reset adapter interrupt indicators */
        set_subchannel_ind(irq_ptr, 1);
        put_indicator(irq_ptr->dsci);
}

int __init qdio_thinint_init(void)
{
        int rc;

        q_indicators = kcalloc(TIQDIO_NR_INDICATORS, sizeof(struct indicator_t),
                               GFP_KERNEL);
        if (!q_indicators)
                return -ENOMEM;

        rc = register_adapter_interrupt(&tiqdio_airq);
        if (rc) {
                DBF_EVENT("RTI:%x", rc);
                kfree(q_indicators);
                return rc;
        }
        return 0;
}

void __exit qdio_thinint_exit(void)
{
        WARN_ON(!list_empty(&tiq_list));
        unregister_adapter_interrupt(&tiqdio_airq);
        kfree(q_indicators);
}