// SPDX-License-Identifier: GPL-2.0
/* Copyright (C) 2019 Arm Ltd.
 *
 * Based on msm_gem_freedreno.c:
 * Copyright (C) 2016 Red Hat
 * Author: Rob Clark <robdclark@gmail.com>
 */

#include <linux/list.h>

#include <drm/drm_device.h>
#include <drm/drm_gem_shmem_helper.h>

#include "panfrost_device.h"
#include "panfrost_gem.h"
#include "panfrost_mmu.h"

static unsigned long
panfrost_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
{
        struct panfrost_device *pfdev = shrinker->private_data;
        struct drm_gem_shmem_object *shmem;
        unsigned long count = 0;

        if (!mutex_trylock(&pfdev->shrinker_lock))
                return 0;

        list_for_each_entry(shmem, &pfdev->shrinker_list, madv_list) {
                if (drm_gem_shmem_is_purgeable(shmem))
                        count += shmem->base.size >> PAGE_SHIFT;
        }

        mutex_unlock(&pfdev->shrinker_lock);

        return count;
}

static bool panfrost_gem_purge(struct drm_gem_object *obj)
{
        struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
        struct panfrost_gem_object *bo = to_panfrost_bo(obj);
        bool ret = false;

        if (atomic_read(&bo->gpu_usecount))
                return false;

        if (!mutex_trylock(&bo->mappings.lock))
                return false;

        if (!dma_resv_trylock(shmem->base.resv))
                goto unlock_mappings;

        panfrost_gem_teardown_mappings_locked(bo);
        drm_gem_shmem_purge_locked(&bo->base);
        ret = true;

        dma_resv_unlock(shmem->base.resv);

unlock_mappings:
        mutex_unlock(&bo->mappings.lock);
        return ret;
}

static unsigned long
panfrost_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
{
        struct panfrost_device *pfdev = shrinker->private_data;
        struct drm_gem_shmem_object *shmem, *tmp;
        unsigned long freed = 0;

        if (!mutex_trylock(&pfdev->shrinker_lock))
                return SHRINK_STOP;

        list_for_each_entry_safe(shmem, tmp, &pfdev->shrinker_list, madv_list) {
                if (freed >= sc->nr_to_scan)
                        break;
                if (drm_gem_shmem_is_purgeable(shmem) &&
                    panfrost_gem_purge(&shmem->base)) {
                        freed += shmem->base.size >> PAGE_SHIFT;
                        list_del_init(&shmem->madv_list);
                }
        }

        mutex_unlock(&pfdev->shrinker_lock);

        if (freed > 0)
                pr_info_ratelimited("Purging %lu bytes\n", freed << PAGE_SHIFT);

        return freed;
}

/**
 * panfrost_gem_shrinker_init - Initialize panfrost shrinker
 * @dev: DRM device
 *
 * This function registers and sets up the panfrost shrinker.
 */
int panfrost_gem_shrinker_init(struct drm_device *dev)
{
        struct panfrost_device *pfdev = to_panfrost_device(dev);

        pfdev->shrinker = shrinker_alloc(0, "drm-panfrost");
        if (!pfdev->shrinker)
                return -ENOMEM;

        pfdev->shrinker->count_objects = panfrost_gem_shrinker_count;
        pfdev->shrinker->scan_objects = panfrost_gem_shrinker_scan;
        pfdev->shrinker->private_data = pfdev;

        shrinker_register(pfdev->shrinker);

        return 0;
}

/**
 * panfrost_gem_shrinker_cleanup - Clean up panfrost shrinker
 * @dev: DRM device
 *
 * This function unregisters the panfrost shrinker.
 */
void panfrost_gem_shrinker_cleanup(struct drm_device *dev)
{
        struct panfrost_device *pfdev = to_panfrost_device(dev);

        if (pfdev->shrinker)
                shrinker_free(pfdev->shrinker);
}