// SPDX-License-Identifier: GPL-2.0+
/*
 * Copyright (C) 2017-2018 Bartosz Golaszewski <brgl@bgdev.pl>
 * Copyright (C) 2020 Bartosz Golaszewski <bgolaszewski@baylibre.com>
 */

#include <linux/irq.h>
#include <linux/irq_sim.h>
#include <linux/irq_work.h>
#include <linux/interrupt.h>
#include <linux/slab.h>

struct irq_sim_work_ctx {
        struct irq_work         work;
        int                     irq_base;
        unsigned int            irq_count;
        unsigned long           *pending;
        struct irq_domain       *domain;
};

struct irq_sim_irq_ctx {
        int                     irqnum;
        bool                    enabled;
        struct irq_sim_work_ctx *work_ctx;
};

static void irq_sim_irqmask(struct irq_data *data)
{
        struct irq_sim_irq_ctx *irq_ctx = irq_data_get_irq_chip_data(data);

        irq_ctx->enabled = false;
}

static void irq_sim_irqunmask(struct irq_data *data)
{
        struct irq_sim_irq_ctx *irq_ctx = irq_data_get_irq_chip_data(data);

        irq_ctx->enabled = true;
}

static int irq_sim_set_type(struct irq_data *data, unsigned int type)
{
        /* We only support rising and falling edge trigger types. */
        if (type & ~IRQ_TYPE_EDGE_BOTH)
                return -EINVAL;

        irqd_set_trigger_type(data, type);

        return 0;
}

static int irq_sim_get_irqchip_state(struct irq_data *data,
                                     enum irqchip_irq_state which, bool *state)
{
        struct irq_sim_irq_ctx *irq_ctx = irq_data_get_irq_chip_data(data);
        irq_hw_number_t hwirq = irqd_to_hwirq(data);

        switch (which) {
        case IRQCHIP_STATE_PENDING:
                if (irq_ctx->enabled)
                        *state = test_bit(hwirq, irq_ctx->work_ctx->pending);
                break;
        default:
                return -EINVAL;
        }

        return 0;
}

static int irq_sim_set_irqchip_state(struct irq_data *data,
                                     enum irqchip_irq_state which, bool state)
{
        struct irq_sim_irq_ctx *irq_ctx = irq_data_get_irq_chip_data(data);
        irq_hw_number_t hwirq = irqd_to_hwirq(data);

        switch (which) {
        case IRQCHIP_STATE_PENDING:
                if (irq_ctx->enabled) {
                        assign_bit(hwirq, irq_ctx->work_ctx->pending, state);
                        if (state)
                                irq_work_queue(&irq_ctx->work_ctx->work);
                }
                break;
        default:
                return -EINVAL;
        }

        return 0;
}

static struct irq_chip irq_sim_irqchip = {
        .name                   = "irq_sim",
        .irq_mask               = irq_sim_irqmask,
        .irq_unmask             = irq_sim_irqunmask,
        .irq_set_type           = irq_sim_set_type,
        .irq_get_irqchip_state  = irq_sim_get_irqchip_state,
        .irq_set_irqchip_state  = irq_sim_set_irqchip_state,
};

static void irq_sim_handle_irq(struct irq_work *work)
{
        struct irq_sim_work_ctx *work_ctx;
        unsigned int offset = 0;
        int irqnum;

        work_ctx = container_of(work, struct irq_sim_work_ctx, work);

        while (!bitmap_empty(work_ctx->pending, work_ctx->irq_count)) {
                offset = find_next_bit(work_ctx->pending,
                                       work_ctx->irq_count, offset);
                clear_bit(offset, work_ctx->pending);
                irqnum = irq_find_mapping(work_ctx->domain, offset);
                handle_simple_irq(irq_to_desc(irqnum));
        }
}

static int irq_sim_domain_map(struct irq_domain *domain,
                              unsigned int virq, irq_hw_number_t hw)
{
        struct irq_sim_work_ctx *work_ctx = domain->host_data;
        struct irq_sim_irq_ctx *irq_ctx;

        irq_ctx = kzalloc(sizeof(*irq_ctx), GFP_KERNEL);
        if (!irq_ctx)
                return -ENOMEM;

        irq_set_chip(virq, &irq_sim_irqchip);
        irq_set_chip_data(virq, irq_ctx);
        irq_set_handler(virq, handle_simple_irq);
        irq_modify_status(virq, IRQ_NOREQUEST | IRQ_NOAUTOEN, IRQ_NOPROBE);
        irq_ctx->work_ctx = work_ctx;

        return 0;
}

static void irq_sim_domain_unmap(struct irq_domain *domain, unsigned int virq)
{
        struct irq_sim_irq_ctx *irq_ctx;
        struct irq_data *irqd;

        irqd = irq_domain_get_irq_data(domain, virq);
        irq_ctx = irq_data_get_irq_chip_data(irqd);

        irq_set_handler(virq, NULL);
        irq_domain_reset_irq_data(irqd);
        kfree(irq_ctx);
}

static const struct irq_domain_ops irq_sim_domain_ops = {
        .map            = irq_sim_domain_map,
        .unmap          = irq_sim_domain_unmap,
};

/**
 * irq_domain_create_sim - Create a new interrupt simulator irq_domain and
 *                         allocate a range of dummy interrupts.
 *
 * @fwnode:     struct fwnode_handle to be associated with this domain.
 * @num_irqs:   Number of interrupts to allocate.
 *
 * On success: return a new irq_domain object.
 * On failure: a negative errno wrapped with ERR_PTR().
 */
struct irq_domain *irq_domain_create_sim(struct fwnode_handle *fwnode,
                                         unsigned int num_irqs)
{
        struct irq_sim_work_ctx *work_ctx;

        work_ctx = kmalloc(sizeof(*work_ctx), GFP_KERNEL);
        if (!work_ctx)
                goto err_out;

        work_ctx->pending = bitmap_zalloc(num_irqs, GFP_KERNEL);
        if (!work_ctx->pending)
                goto err_free_work_ctx;

        work_ctx->domain = irq_domain_create_linear(fwnode, num_irqs,
                                                    &irq_sim_domain_ops,
                                                    work_ctx);
        if (!work_ctx->domain)
                goto err_free_bitmap;

        work_ctx->irq_count = num_irqs;
        init_irq_work(&work_ctx->work, irq_sim_handle_irq);

        return work_ctx->domain;

err_free_bitmap:
        bitmap_free(work_ctx->pending);
err_free_work_ctx:
        kfree(work_ctx);
err_out:
        return ERR_PTR(-ENOMEM);
}
EXPORT_SYMBOL_GPL(irq_domain_create_sim);

/**
 * irq_domain_remove_sim - Deinitialize the interrupt simulator domain: free
 *                         the interrupt descriptors and allocated memory.
 *
 * @domain:     The interrupt simulator domain to tear down.
 */
void irq_domain_remove_sim(struct irq_domain *domain)
{
        struct irq_sim_work_ctx *work_ctx = domain->host_data;

        irq_work_sync(&work_ctx->work);
        bitmap_free(work_ctx->pending);
        kfree(work_ctx);

        irq_domain_remove(domain);
}
EXPORT_SYMBOL_GPL(irq_domain_remove_sim);

static void devm_irq_domain_remove_sim(void *data)
{
        struct irq_domain *domain = data;

        irq_domain_remove_sim(domain);
}

/**
 * devm_irq_domain_create_sim - Create a new interrupt simulator for
 *                              a managed device.
 *
 * @dev:        Device to initialize the simulator object for.
 * @fwnode:     struct fwnode_handle to be associated with this domain.
 * @num_irqs:   Number of interrupts to allocate
 *
 * On success: return a new irq_domain object.
 * On failure: a negative errno wrapped with ERR_PTR().
 */
struct irq_domain *devm_irq_domain_create_sim(struct device *dev,
                                              struct fwnode_handle *fwnode,
                                              unsigned int num_irqs)
{
        struct irq_domain *domain;
        int ret;

        domain = irq_domain_create_sim(fwnode, num_irqs);
        if (IS_ERR(domain))
                return domain;

        ret = devm_add_action_or_reset(dev, devm_irq_domain_remove_sim, domain);
        if (ret)
                return ERR_PTR(ret);

        return domain;
}
EXPORT_SYMBOL_GPL(devm_irq_domain_create_sim);