/*
 * linux/kernel/irq/ipi.c
 *
 * Copyright (C) 2015 Imagination Technologies Ltd
 * Author: Qais Yousef <qais.yousef@imgtec.com>
 *
 * This file contains driver APIs to the IPI subsystem.
 */

#define pr_fmt(fmt) "genirq/ipi: " fmt

#include <linux/irqdomain.h>
#include <linux/irq.h>

/**
 * irq_reserve_ipi() - Setup an IPI to destination cpumask
 * @domain:     IPI domain
 * @dest:       cpumask of cpus which can receive the IPI
 *
 * Allocate a virq that can be used to send IPI to any CPU in dest mask.
 *
 * On success it'll return linux irq number and error code on failure
 */
int irq_reserve_ipi(struct irq_domain *domain,
                             const struct cpumask *dest)
{
        unsigned int nr_irqs, offset;
        struct irq_data *data;
        int virq, i;

        if (!domain ||!irq_domain_is_ipi(domain)) {
                pr_warn("Reservation on a non IPI domain\n");
                return -EINVAL;
        }

        if (!cpumask_subset(dest, cpu_possible_mask)) {
                pr_warn("Reservation is not in possible_cpu_mask\n");
                return -EINVAL;
        }

        nr_irqs = cpumask_weight(dest);
        if (!nr_irqs) {
                pr_warn("Reservation for empty destination mask\n");
                return -EINVAL;
        }

        if (irq_domain_is_ipi_single(domain)) {
                /*
                 * If the underlying implementation uses a single HW irq on
                 * all cpus then we only need a single Linux irq number for
                 * it. We have no restrictions vs. the destination mask. The
                 * underlying implementation can deal with holes nicely.
                 */
                nr_irqs = 1;
                offset = 0;
        } else {
                unsigned int next;

                /*
                 * The IPI requires a seperate HW irq on each CPU. We require
                 * that the destination mask is consecutive. If an
                 * implementation needs to support holes, it can reserve
                 * several IPI ranges.
                 */
                offset = cpumask_first(dest);
                /*
                 * Find a hole and if found look for another set bit after the
                 * hole. For now we don't support this scenario.
                 */
                next = cpumask_next_zero(offset, dest);
                if (next < nr_cpu_ids)
                        next = cpumask_next(next, dest);
                if (next < nr_cpu_ids) {
                        pr_warn("Destination mask has holes\n");
                        return -EINVAL;
                }
        }

        virq = irq_domain_alloc_descs(-1, nr_irqs, 0, NUMA_NO_NODE, NULL);
        if (virq <= 0) {
                pr_warn("Can't reserve IPI, failed to alloc descs\n");
                return -ENOMEM;
        }

        virq = __irq_domain_alloc_irqs(domain, virq, nr_irqs, NUMA_NO_NODE,
                                       (void *) dest, true, NULL);

        if (virq <= 0) {
                pr_warn("Can't reserve IPI, failed to alloc hw irqs\n");
                goto free_descs;
        }

        for (i = 0; i < nr_irqs; i++) {
                data = irq_get_irq_data(virq + i);
                cpumask_copy(data->common->affinity, dest);
                data->common->ipi_offset = offset;
                irq_set_status_flags(virq + i, IRQ_NO_BALANCING);
        }
        return virq;

free_descs:
        irq_free_descs(virq, nr_irqs);
        return -EBUSY;
}

/**
 * irq_destroy_ipi() - unreserve an IPI that was previously allocated
 * @irq:        linux irq number to be destroyed
 * @dest:       cpumask of cpus which should have the IPI removed
 *
 * The IPIs allocated with irq_reserve_ipi() are retuerned to the system
 * destroying all virqs associated with them.
 *
 * Return 0 on success or error code on failure.
 */
int irq_destroy_ipi(unsigned int irq, const struct cpumask *dest)
{
        struct irq_data *data = irq_get_irq_data(irq);
        struct cpumask *ipimask = data ? irq_data_get_affinity_mask(data) : NULL;
        struct irq_domain *domain;
        unsigned int nr_irqs;

        if (!irq || !data || !ipimask)
                return -EINVAL;

        domain = data->domain;
        if (WARN_ON(domain == NULL))
                return -EINVAL;

        if (!irq_domain_is_ipi(domain)) {
                pr_warn("Trying to destroy a non IPI domain!\n");
                return -EINVAL;
        }

        if (WARN_ON(!cpumask_subset(dest, ipimask)))
                /*
                 * Must be destroying a subset of CPUs to which this IPI
                 * was set up to target
                 */
                return -EINVAL;

        if (irq_domain_is_ipi_per_cpu(domain)) {
                irq = irq + cpumask_first(dest) - data->common->ipi_offset;
                nr_irqs = cpumask_weight(dest);
        } else {
                nr_irqs = 1;
        }

        irq_domain_free_irqs(irq, nr_irqs);
        return 0;
}

/**
 * ipi_get_hwirq - Get the hwirq associated with an IPI to a cpu
 * @irq:        linux irq number
 * @cpu:        the target cpu
 *
 * When dealing with coprocessors IPI, we need to inform the coprocessor of
 * the hwirq it needs to use to receive and send IPIs.
 *
 * Returns hwirq value on success and INVALID_HWIRQ on failure.
 */
irq_hw_number_t ipi_get_hwirq(unsigned int irq, unsigned int cpu)
{
        struct irq_data *data = irq_get_irq_data(irq);
        struct cpumask *ipimask = data ? irq_data_get_affinity_mask(data) : NULL;

        if (!data || !ipimask || cpu >= nr_cpu_ids)
                return INVALID_HWIRQ;

        if (!cpumask_test_cpu(cpu, ipimask))
                return INVALID_HWIRQ;

        /*
         * Get the real hardware irq number if the underlying implementation
         * uses a seperate irq per cpu. If the underlying implementation uses
         * a single hardware irq for all cpus then the IPI send mechanism
         * needs to take care of the cpu destinations.
         */
        if (irq_domain_is_ipi_per_cpu(data->domain))
                data = irq_get_irq_data(irq + cpu - data->common->ipi_offset);

        return data ? irqd_to_hwirq(data) : INVALID_HWIRQ;
}
EXPORT_SYMBOL_GPL(ipi_get_hwirq);

static int ipi_send_verify(struct irq_chip *chip, struct irq_data *data,
                           const struct cpumask *dest, unsigned int cpu)
{
        struct cpumask *ipimask = irq_data_get_affinity_mask(data);

        if (!chip || !ipimask)
                return -EINVAL;

        if (!chip->ipi_send_single && !chip->ipi_send_mask)
                return -EINVAL;

        if (cpu >= nr_cpu_ids)
                return -EINVAL;

        if (dest) {
                if (!cpumask_subset(dest, ipimask))
                        return -EINVAL;
        } else {
                if (!cpumask_test_cpu(cpu, ipimask))
                        return -EINVAL;
        }
        return 0;
}

/**
 * __ipi_send_single - send an IPI to a target Linux SMP CPU
 * @desc:       pointer to irq_desc of the IRQ
 * @cpu:        destination CPU, must in the destination mask passed to
 *              irq_reserve_ipi()
 *
 * This function is for architecture or core code to speed up IPI sending. Not
 * usable from driver code.
 *
 * Returns zero on success and negative error number on failure.
 */
int __ipi_send_single(struct irq_desc *desc, unsigned int cpu)
{
        struct irq_data *data = irq_desc_get_irq_data(desc);
        struct irq_chip *chip = irq_data_get_irq_chip(data);

#ifdef DEBUG
        /*
         * Minimise the overhead by omitting the checks for Linux SMP IPIs.
         * Since the callers should be arch or core code which is generally
         * trusted, only check for errors when debugging.
         */
        if (WARN_ON_ONCE(ipi_send_verify(chip, data, NULL, cpu)))
                return -EINVAL;
#endif
        if (!chip->ipi_send_single) {
                chip->ipi_send_mask(data, cpumask_of(cpu));
                return 0;
        }

        /* FIXME: Store this information in irqdata flags */
        if (irq_domain_is_ipi_per_cpu(data->domain) &&
            cpu != data->common->ipi_offset) {
                /* use the correct data for that cpu */
                unsigned irq = data->irq + cpu - data->common->ipi_offset;

                data = irq_get_irq_data(irq);
        }
        chip->ipi_send_single(data, cpu);
        return 0;
}

/**
 * ipi_send_mask - send an IPI to target Linux SMP CPU(s)
 * @desc:       pointer to irq_desc of the IRQ
 * @dest:       dest CPU(s), must be a subset of the mask passed to
 *              irq_reserve_ipi()
 *
 * This function is for architecture or core code to speed up IPI sending. Not
 * usable from driver code.
 *
 * Returns zero on success and negative error number on failure.
 */
int __ipi_send_mask(struct irq_desc *desc, const struct cpumask *dest)
{
        struct irq_data *data = irq_desc_get_irq_data(desc);
        struct irq_chip *chip = irq_data_get_irq_chip(data);
        unsigned int cpu;

#ifdef DEBUG
        /*
         * Minimise the overhead by omitting the checks for Linux SMP IPIs.
         * Since the callers should be arch or core code which is generally
         * trusted, only check for errors when debugging.
         */
        if (WARN_ON_ONCE(ipi_send_verify(chip, data, dest, 0)))
                return -EINVAL;
#endif
        if (chip->ipi_send_mask) {
                chip->ipi_send_mask(data, dest);
                return 0;
        }

        if (irq_domain_is_ipi_per_cpu(data->domain)) {
                unsigned int base = data->irq;

                for_each_cpu(cpu, dest) {
                        unsigned irq = base + cpu - data->common->ipi_offset;

                        data = irq_get_irq_data(irq);
                        chip->ipi_send_single(data, cpu);
                }
        } else {
                for_each_cpu(cpu, dest)
                        chip->ipi_send_single(data, cpu);
        }
        return 0;
}

/**
 * ipi_send_single - Send an IPI to a single CPU
 * @virq:       linux irq number from irq_reserve_ipi()
 * @cpu:        destination CPU, must in the destination mask passed to
 *              irq_reserve_ipi()
 *
 * Returns zero on success and negative error number on failure.
 */
int ipi_send_single(unsigned int virq, unsigned int cpu)
{
        struct irq_desc *desc = irq_to_desc(virq);
        struct irq_data *data = desc ? irq_desc_get_irq_data(desc) : NULL;
        struct irq_chip *chip = data ? irq_data_get_irq_chip(data) : NULL;

        if (WARN_ON_ONCE(ipi_send_verify(chip, data, NULL, cpu)))
                return -EINVAL;

        return __ipi_send_single(desc, cpu);
}
EXPORT_SYMBOL_GPL(ipi_send_single);

/**
 * ipi_send_mask - Send an IPI to target CPU(s)
 * @virq:       linux irq number from irq_reserve_ipi()
 * @dest:       dest CPU(s), must be a subset of the mask passed to
 *              irq_reserve_ipi()
 *
 * Returns zero on success and negative error number on failure.
 */
int ipi_send_mask(unsigned int virq, const struct cpumask *dest)
{
        struct irq_desc *desc = irq_to_desc(virq);
        struct irq_data *data = desc ? irq_desc_get_irq_data(desc) : NULL;
        struct irq_chip *chip = data ? irq_data_get_irq_chip(data) : NULL;

        if (WARN_ON_ONCE(ipi_send_verify(chip, data, dest, 0)))
                return -EINVAL;

        return __ipi_send_mask(desc, dest);
}
EXPORT_SYMBOL_GPL(ipi_send_mask);