// 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;
};

struct irq_sim_devres {
	struct irq_domain	*domain;
};

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.
 *
 * @fnode:      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_release_sim(struct device *dev, void *res)
{
	struct irq_sim_devres *this = res;

	irq_domain_remove_sim(this->domain);
}

/**
 * devm_irq_domain_create_sim - Create a new interrupt simulator for
 *                              a managed device.
 *
 * @dev:        Device to initialize the simulator object for.
 * @fnode:      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_sim_devres *dr;

	dr = devres_alloc(devm_irq_domain_release_sim,
			  sizeof(*dr), GFP_KERNEL);
	if (!dr)
		return ERR_PTR(-ENOMEM);

	dr->domain = irq_domain_create_sim(fwnode, num_irqs);
	if (IS_ERR(dr->domain)) {
		devres_free(dr);
		return dr->domain;
	}

	devres_add(dev, dr);
	return dr->domain;
}
EXPORT_SYMBOL_GPL(devm_irq_domain_create_sim);