// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2021, NVIDIA Corporation.
 */

#include <linux/completion.h>
#include <linux/device.h>
#include <linux/host1x_context_bus.h>
#include <linux/kref.h>
#include <linux/list.h>
#include <linux/moduleparam.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/pid.h>
#include <linux/slab.h>

#include "context.h"
#include "dev.h"

static bool static_context_alloc;
module_param(static_context_alloc, bool, 0644);
MODULE_PARM_DESC(static_context_alloc, "If enabled, memory contexts are allocated immediately on channel open and cannot be relinquished while a channel is open");

static void host1x_memory_context_release(struct device *dev)
{
	/* context device is freed in host1x_memory_context_list_free() */
}

int host1x_memory_context_list_init(struct host1x *host1x)
{
	struct host1x_memory_context_list *cdl = &host1x->context_list;
	struct device_node *node = host1x->dev->of_node;
	struct host1x_hw_memory_context *ctx;
	unsigned int devs, i;
	int err;

	cdl->devs = NULL;
	cdl->len = 0;
	mutex_init(&cdl->lock);
	INIT_LIST_HEAD(&cdl->waiters);

	err = of_property_count_u32_elems(node, "iommu-map");
	if (err < 0)
		return 0;

	devs = 0;

	for (i = 0; i < err / 4; i++) {
		u32 length;

		of_property_read_u32_index(node, "iommu-map", i * 4 + 3, &length);
		devs += length;
	}

	cdl->len = devs;
	cdl->devs = kzalloc_objs(*cdl->devs, cdl->len);
	if (!cdl->devs)
		return -ENOMEM;

	for (i = 0; i < cdl->len; i++) {
		ctx = &cdl->devs[i];

		ctx->host = host1x;
		INIT_LIST_HEAD(&ctx->owners);

		device_initialize(&ctx->dev);

		/*
		 * Due to an issue with T194 NVENC, only 38 bits can be used.
		 * Anyway, 256GiB of IOVA ought to be enough for anyone.
		 */
		ctx->dma_mask = DMA_BIT_MASK(38);
		ctx->dev.dma_mask = &ctx->dma_mask;
		ctx->dev.coherent_dma_mask = ctx->dma_mask;
		dev_set_name(&ctx->dev, "host1x-ctx.%d", i);
		ctx->dev.bus = &host1x_context_device_bus_type;
		ctx->dev.parent = host1x->dev;
		ctx->dev.release = host1x_memory_context_release;

		ctx->dev.dma_parms = &ctx->dma_parms;
		dma_set_max_seg_size(&ctx->dev, UINT_MAX);

		err = device_add(&ctx->dev);
		if (err) {
			dev_err(host1x->dev, "could not add context device %d: %d\n", i, err);
			put_device(&ctx->dev);
			goto unreg_devices;
		}

		err = of_dma_configure_id(&ctx->dev, node, true, &i);
		if (err) {
			dev_err(host1x->dev, "IOMMU configuration failed for context device %d: %d\n",
				i, err);
			device_unregister(&ctx->dev);
			goto unreg_devices;
		}

		if (!tegra_dev_iommu_get_stream_id(&ctx->dev, &ctx->stream_id) ||
		    !device_iommu_mapped(&ctx->dev)) {
			dev_err(host1x->dev, "Context device %d has no IOMMU!\n", i);
			device_unregister(&ctx->dev);

			/*
			 * This means that if IOMMU is disabled but context devices
			 * are defined in the device tree, Host1x will fail to probe.
			 * That's probably OK in this time and age.
			 */
			err = -EINVAL;

			goto unreg_devices;
		}
	}

	return 0;

unreg_devices:
	while (i--)
		device_unregister(&cdl->devs[i].dev);

	kfree(cdl->devs);
	cdl->devs = NULL;
	cdl->len = 0;

	return err;
}

void host1x_memory_context_list_free(struct host1x_memory_context_list *cdl)
{
	unsigned int i;

	for (i = 0; i < cdl->len; i++)
		device_unregister(&cdl->devs[i].dev);

	kfree(cdl->devs);
	cdl->len = 0;
}

static bool hw_usable_for_dev(struct host1x_hw_memory_context *hw, struct device *dev)
{
	return hw->dev.iommu->iommu_dev == dev->iommu->iommu_dev;
}

static struct host1x_hw_memory_context *
host1x_memory_context_alloc_hw_locked(struct host1x *host1x, struct device *dev,
				      struct pid *pid)
{
	struct host1x_memory_context_list *cdl = &host1x->context_list;
	struct host1x_hw_memory_context *free = NULL, *can_steal = NULL;
	struct host1x_memory_context *ctx;
	int i;

	if (!cdl->len)
		return ERR_PTR(-EOPNOTSUPP);

	for (i = 0; i < cdl->len; i++) {
		struct host1x_hw_memory_context *cd = &cdl->devs[i];

		if (!hw_usable_for_dev(cd, dev))
			continue;

		if (cd->owner == pid) {
			refcount_inc(&cd->ref);
			return cd;
		} else if (!cd->owner && !free) {
			free = cd;
		} else if (refcount_read(&cd->active) == 0) {
			can_steal = cd;
		}
	}

	if (free)
		goto found;

	/* Steal */

	if (!can_steal || static_context_alloc)
		return ERR_PTR(-EBUSY);

	list_for_each_entry(ctx, &can_steal->owners, entry) {
		struct host1x_context_mapping *mapping;

		ctx->hw = NULL;

		list_for_each_entry(mapping, &ctx->mappings, entry) {
			host1x_bo_unpin(mapping->mapping);
			mapping->mapping = NULL;
		}
	}

	put_pid(can_steal->owner);

	free = can_steal;

found:
	refcount_set(&free->ref, 1);
	free->owner = get_pid(pid);
	INIT_LIST_HEAD(&free->owners);

	return free;
}

static void host1x_memory_context_hw_put(struct host1x_hw_memory_context *cd)
{
	if (refcount_dec_and_test(&cd->ref)) {
		put_pid(cd->owner);
		cd->owner = NULL;
	}
}

/**
 * host1x_memory_context_alloc() - allocate a logical memory context
 * @host1x: host1x instance
 * @dev: engine device that will own the context
 * @pid: PID (TGID) of the process the context is allocated for
 *
 * Allocate a logical memory context. The context has no backing hardware memory
 * context until host1x_memory_context_active() is called unless static context
 * allocation is enabled.
 *
 * Return: pointer to the new context, or an ERR_PTR() on failure.
 * ERR_PTR(-EOPNOTSUPP) is returned if the platform has no hardware memory
 * contexts.
 */
struct host1x_memory_context *host1x_memory_context_alloc(struct host1x *host1x,
							  struct device *dev,
							  struct pid *pid)
{
	struct host1x_memory_context_list *cdl = &host1x->context_list;
	struct host1x_memory_context *ctx;
	int err;

	if (!cdl->len)
		return ERR_PTR(-EOPNOTSUPP);

	ctx = kzalloc_obj(*ctx, GFP_KERNEL);
	if (!ctx)
		return ERR_PTR(-ENOMEM);

	ctx->host = host1x;
	ctx->dev = dev;
	ctx->pid = get_pid(pid);

	refcount_set(&ctx->ref, 1);
	INIT_LIST_HEAD(&ctx->mappings);

	if (static_context_alloc) {
		err = host1x_memory_context_active(ctx);
		if (err) {
			put_pid(ctx->pid);
			kfree(ctx);
			return ERR_PTR(err);
		}

		ctx->static_alloc = true;
	}

	return ctx;
}
EXPORT_SYMBOL_GPL(host1x_memory_context_alloc);

struct hw_alloc_waiter {
	struct completion wait; /* Completion to wait for free hw context */
	struct list_head entry;
	struct device *dev;
};

/**
 * host1x_memory_context_active() - mark a memory context as in use
 * @ctx: memory context
 *
 * Bind a hardware memory context to @ctx and map all of its stored mappings,
 * allocating or stealing a hardware context from an idle context if needed.
 * While the context is active its hardware context cannot be stolen away.
 *
 * Each successful call must be balanced by exactly one
 * host1x_memory_context_inactive() call.
 *
 * May sleep, and may block until a hardware context becomes available unless
 * static allocation is in use. Must be called in process context.
 *
 * Return: 0 on success or a negative error code. -EBUSY is returned if no
 * hardware context could be obtained and static context allocation is enabled.
 */
int host1x_memory_context_active(struct host1x_memory_context *ctx)
{
	struct host1x_memory_context_list *cdl = &ctx->host->context_list;
	struct host1x_context_mapping *mapping;
	struct host1x_hw_memory_context *hw;
	struct hw_alloc_waiter waiter;
	bool retrying = false;
	int err = 0;

	mutex_lock(&cdl->lock);

retry:
	if (ctx->hw)
		goto have_hw;

	hw = host1x_memory_context_alloc_hw_locked(ctx->host, ctx->dev, ctx->pid);
	if (PTR_ERR(hw) == -EBUSY) {
		/* All contexts busy. Wait for free context. */
		if (static_context_alloc) {
			dev_warn(ctx->dev, "%s: all memory contexts are busy\n", current->comm);
			err = -EBUSY;
			goto unlock;
		}
		if (!retrying)
			dev_warn(ctx->dev, "%s: all memory contexts are busy, waiting\n",
				 current->comm);

		init_completion(&waiter.wait);
		waiter.dev = ctx->dev;
		list_add(&waiter.entry, &cdl->waiters);

		mutex_unlock(&cdl->lock);
		err = wait_for_completion_interruptible(&waiter.wait);
		mutex_lock(&cdl->lock);

		list_del(&waiter.entry);
		if (err)
			goto unlock;

		retrying = true;
		goto retry;
	}
	if (IS_ERR(hw)) {
		err = PTR_ERR(hw);
		goto unlock;
	}

	ctx->hw = hw;
	list_add(&ctx->entry, &hw->owners);

	list_for_each_entry(mapping, &ctx->mappings, entry) {
		mapping->mapping = host1x_bo_pin(&hw->dev, mapping->bo,
						 mapping->direction, NULL);
		if (IS_ERR(mapping->mapping)) {
			err = PTR_ERR(mapping->mapping);
			mapping->mapping = NULL;
			goto unpin;
		}
	}

have_hw:
	/* We're just counting active users. No need to do anything on 0->1 transition.*/
	if (!refcount_inc_not_zero(&ctx->hw->active))
		refcount_set(&ctx->hw->active, 1);

	mutex_unlock(&cdl->lock);

	return 0;

unpin:
	list_for_each_entry(mapping, &ctx->mappings, entry) {
		if (mapping->mapping) {
			host1x_bo_unpin(mapping->mapping);
			mapping->mapping = NULL;
		}
	}

	host1x_memory_context_hw_put(ctx->hw);
	list_del(&ctx->entry);
	ctx->hw = NULL;
unlock:
	mutex_unlock(&cdl->lock);
	return err;
}
EXPORT_SYMBOL_GPL(host1x_memory_context_active);

/**
 * host1x_memory_context_map() - add a buffer mapping to a memory context
 * @ctx: memory context
 * @bo: buffer object to map
 * @direction: DMA direction of the mapping
 *
 * Register a mapping of @bo on @ctx. If @ctx currently has a hardware context
 * bound, the buffer is mapped immediately; otherwise it is pinned the next time
 * the context is made active. The mapping is unmapped and freed by
 * host1x_memory_context_unmap().
 *
 * Return: pointer to the mapping, or an ERR_PTR() on failure.
 */
struct host1x_context_mapping *host1x_memory_context_map(struct host1x_memory_context *ctx,
							 struct host1x_bo *bo,
							 enum dma_data_direction direction)
{
	struct host1x_memory_context_list *cdl = &ctx->host->context_list;
	struct host1x_context_mapping *m;
	struct host1x_bo_mapping *bo_m;

	m = kzalloc_obj(*m, GFP_KERNEL);
	if (!m)
		return ERR_PTR(-ENOMEM);

	m->host = ctx->host;
	m->bo = bo;
	m->direction = direction;

	mutex_lock(&cdl->lock);

	if (ctx->hw) {
		bo_m = host1x_bo_pin(&ctx->hw->dev, bo, direction, NULL);
		if (IS_ERR(bo_m)) {
			mutex_unlock(&cdl->lock);
			kfree(m);

			return ERR_CAST(bo_m);
		}

		m->mapping = bo_m;
	}

	list_add(&m->entry, &ctx->mappings);

	mutex_unlock(&cdl->lock);

	return m;
}
EXPORT_SYMBOL_GPL(host1x_memory_context_map);

/**
 * host1x_memory_context_unmap() - remove a buffer mapping from a memory context
 * @m: mapping previously returned by host1x_memory_context_map()
 *
 * Unmap the buffer if it is currently mapped, and free the mapping.
 */
void host1x_memory_context_unmap(struct host1x_context_mapping *m)
{
	struct host1x_memory_context_list *cdl = &m->host->context_list;

	mutex_lock(&cdl->lock);

	list_del(&m->entry);

	mutex_unlock(&cdl->lock);

	if (m->mapping)
		host1x_bo_unpin(m->mapping);

	kfree(m);
}
EXPORT_SYMBOL_GPL(host1x_memory_context_unmap);

static void host1x_memory_context_inactive_locked(struct host1x_memory_context *ctx)
{
	struct host1x_memory_context_list *cdl = &ctx->host->context_list;
	struct hw_alloc_waiter *waiter;

	if (refcount_dec_and_test(&ctx->hw->active)) {
		/* Hardware context becomes eligible for stealing */
		list_for_each_entry(waiter, &cdl->waiters, entry) {
			if (!hw_usable_for_dev(ctx->hw, waiter->dev))
				continue;

			complete(&waiter->wait);

			/*
			 * Need to wake up all waiters -- there could be multiple from
			 * the same process that can use the same freed hardware context.
			 */
		}
	}
}

/**
 * host1x_memory_context_inactive() - mark a memory context as no longer in use
 * @ctx: memory context
 *
 * Drop one active reference taken by host1x_memory_context_active(). When the
 * last active reference is dropped, the backing hardware context becomes
 * eligible to be stolen by another context, and any waiters are woken.
 *
 * Must be called exactly once for each successful
 * host1x_memory_context_active().
 */
void host1x_memory_context_inactive(struct host1x_memory_context *ctx)
{
	struct host1x_memory_context_list *cdl = &ctx->host->context_list;

	mutex_lock(&cdl->lock);

	host1x_memory_context_inactive_locked(ctx);

	mutex_unlock(&cdl->lock);
}
EXPORT_SYMBOL_GPL(host1x_memory_context_inactive);

/**
 * host1x_memory_context_get() - take a reference to a memory context
 * @ctx: memory context
 */
void host1x_memory_context_get(struct host1x_memory_context *ctx)
{
	refcount_inc(&ctx->ref);
}
EXPORT_SYMBOL_GPL(host1x_memory_context_get);

/**
 * host1x_memory_context_put() - release a reference to a memory context
 * @ctx: memory context
 *
 * Drop a reference taken by host1x_memory_context_alloc() or
 * host1x_memory_context_get(). When the last reference is dropped the context
 * is detached from its hardware context and freed.
 */
void host1x_memory_context_put(struct host1x_memory_context *ctx)
{
	struct host1x_memory_context_list *cdl = &ctx->host->context_list;

	if (refcount_dec_and_mutex_lock(&ctx->ref, &cdl->lock)) {
		if (ctx->static_alloc)
			host1x_memory_context_inactive_locked(ctx);

		if (ctx->hw) {
			list_del(&ctx->entry);

			host1x_memory_context_hw_put(ctx->hw);
			ctx->hw = NULL;

			WARN_ON(!list_empty(&ctx->mappings));
		}

		put_pid(ctx->pid);
		mutex_unlock(&cdl->lock);
		kfree(ctx);
	}
}
EXPORT_SYMBOL_GPL(host1x_memory_context_put);