/*
 * SPDX-License-Identifier: MIT
 *
 * Copyright © 2016 Intel Corporation
 */

#include "i915_scatterlist.h"

#include "i915_buddy.h"
#include "i915_ttm_buddy_manager.h"

#include <drm/drm_mm.h>

#include <linux/slab.h>

bool i915_sg_trim(struct sg_table *orig_st)
{
        struct sg_table new_st;
        struct scatterlist *sg, *new_sg;
        unsigned int i;

        if (orig_st->nents == orig_st->orig_nents)
                return false;

        if (sg_alloc_table(&new_st, orig_st->nents, GFP_KERNEL | __GFP_NOWARN))
                return false;

        new_sg = new_st.sgl;
        for_each_sg(orig_st->sgl, sg, orig_st->nents, i) {
                sg_set_page(new_sg, sg_page(sg), sg->length, 0);
                sg_dma_address(new_sg) = sg_dma_address(sg);
                sg_dma_len(new_sg) = sg_dma_len(sg);

                new_sg = sg_next(new_sg);
        }
        GEM_BUG_ON(new_sg); /* Should walk exactly nents and hit the end */

        sg_free_table(orig_st);

        *orig_st = new_st;
        return true;
}

/**
 * i915_sg_from_mm_node - Create an sg_table from a struct drm_mm_node
 * @node: The drm_mm_node.
 * @region_start: An offset to add to the dma addresses of the sg list.
 *
 * Create a struct sg_table, initializing it from a struct drm_mm_node,
 * taking a maximum segment length into account, splitting into segments
 * if necessary.
 *
 * Return: A pointer to a kmalloced struct sg_table on success, negative
 * error code cast to an error pointer on failure.
 */
struct sg_table *i915_sg_from_mm_node(const struct drm_mm_node *node,
                                      u64 region_start)
{
        const u64 max_segment = SZ_1G; /* Do we have a limit on this? */
        u64 segment_pages = max_segment >> PAGE_SHIFT;
        u64 block_size, offset, prev_end;
        struct sg_table *st;
        struct scatterlist *sg;

        st = kmalloc(sizeof(*st), GFP_KERNEL);
        if (!st)
                return ERR_PTR(-ENOMEM);

        if (sg_alloc_table(st, DIV_ROUND_UP(node->size, segment_pages),
                           GFP_KERNEL)) {
                kfree(st);
                return ERR_PTR(-ENOMEM);
        }

        sg = st->sgl;
        st->nents = 0;
        prev_end = (resource_size_t)-1;
        block_size = node->size << PAGE_SHIFT;
        offset = node->start << PAGE_SHIFT;

        while (block_size) {
                u64 len;

                if (offset != prev_end || sg->length >= max_segment) {
                        if (st->nents)
                                sg = __sg_next(sg);

                        sg_dma_address(sg) = region_start + offset;
                        sg_dma_len(sg) = 0;
                        sg->length = 0;
                        st->nents++;
                }

                len = min(block_size, max_segment - sg->length);
                sg->length += len;
                sg_dma_len(sg) += len;

                offset += len;
                block_size -= len;

                prev_end = offset;
        }

        sg_mark_end(sg);
        i915_sg_trim(st);

        return st;
}

/**
 * i915_sg_from_buddy_resource - Create an sg_table from a struct
 * i915_buddy_block list
 * @res: The struct i915_ttm_buddy_resource.
 * @region_start: An offset to add to the dma addresses of the sg list.
 *
 * Create a struct sg_table, initializing it from struct i915_buddy_block list,
 * taking a maximum segment length into account, splitting into segments
 * if necessary.
 *
 * Return: A pointer to a kmalloced struct sg_table on success, negative
 * error code cast to an error pointer on failure.
 */
struct sg_table *i915_sg_from_buddy_resource(struct ttm_resource *res,
                                             u64 region_start)
{
        struct i915_ttm_buddy_resource *bman_res = to_ttm_buddy_resource(res);
        const u64 size = res->num_pages << PAGE_SHIFT;
        const u64 max_segment = rounddown(UINT_MAX, PAGE_SIZE);
        struct i915_buddy_mm *mm = bman_res->mm;
        struct list_head *blocks = &bman_res->blocks;
        struct i915_buddy_block *block;
        struct scatterlist *sg;
        struct sg_table *st;
        resource_size_t prev_end;

        GEM_BUG_ON(list_empty(blocks));

        st = kmalloc(sizeof(*st), GFP_KERNEL);
        if (!st)
                return ERR_PTR(-ENOMEM);

        if (sg_alloc_table(st, res->num_pages, GFP_KERNEL)) {
                kfree(st);
                return ERR_PTR(-ENOMEM);
        }

        sg = st->sgl;
        st->nents = 0;
        prev_end = (resource_size_t)-1;

        list_for_each_entry(block, blocks, link) {
                u64 block_size, offset;

                block_size = min_t(u64, size, i915_buddy_block_size(mm, block));
                offset = i915_buddy_block_offset(block);

                while (block_size) {
                        u64 len;

                        if (offset != prev_end || sg->length >= max_segment) {
                                if (st->nents)
                                        sg = __sg_next(sg);

                                sg_dma_address(sg) = region_start + offset;
                                sg_dma_len(sg) = 0;
                                sg->length = 0;
                                st->nents++;
                        }

                        len = min(block_size, max_segment - sg->length);
                        sg->length += len;
                        sg_dma_len(sg) += len;

                        offset += len;
                        block_size -= len;

                        prev_end = offset;
                }
        }

        sg_mark_end(sg);
        i915_sg_trim(st);

        return st;
}

#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
#include "selftests/scatterlist.c"
#endif