// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Scatter-Gather buffer
 *
 *  Copyright (c) by Takashi Iwai <tiwai@suse.de>
 */

#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/vmalloc.h>
#include <linux/export.h>
#include <sound/memalloc.h>
#include "memalloc_local.h"

struct snd_sg_page {
        void *buf;
        dma_addr_t addr;
};

struct snd_sg_buf {
        int size;       /* allocated byte size */
        int pages;      /* allocated pages */
        int tblsize;    /* allocated table size */
        struct snd_sg_page *table;      /* address table */
        struct page **page_table;       /* page table (for vmap/vunmap) */
        struct device *dev;
};

/* table entries are align to 32 */
#define SGBUF_TBL_ALIGN         32
#define sgbuf_align_table(tbl)  ALIGN((tbl), SGBUF_TBL_ALIGN)

static void snd_dma_sg_free(struct snd_dma_buffer *dmab)
{
        struct snd_sg_buf *sgbuf = dmab->private_data;
        struct snd_dma_buffer tmpb;
        int i;

        if (!sgbuf)
                return;

        vunmap(dmab->area);
        dmab->area = NULL;

        tmpb.dev.type = SNDRV_DMA_TYPE_DEV;
        if (dmab->dev.type == SNDRV_DMA_TYPE_DEV_WC_SG)
                tmpb.dev.type = SNDRV_DMA_TYPE_DEV_WC;
        tmpb.dev.dev = sgbuf->dev;
        for (i = 0; i < sgbuf->pages; i++) {
                if (!(sgbuf->table[i].addr & ~PAGE_MASK))
                        continue; /* continuous pages */
                tmpb.area = sgbuf->table[i].buf;
                tmpb.addr = sgbuf->table[i].addr & PAGE_MASK;
                tmpb.bytes = (sgbuf->table[i].addr & ~PAGE_MASK) << PAGE_SHIFT;
                snd_dma_free_pages(&tmpb);
        }

        kfree(sgbuf->table);
        kfree(sgbuf->page_table);
        kfree(sgbuf);
        dmab->private_data = NULL;
}

#define MAX_ALLOC_PAGES         32

static void *snd_dma_sg_alloc(struct snd_dma_buffer *dmab, size_t size)
{
        struct snd_sg_buf *sgbuf;
        unsigned int i, pages, chunk, maxpages;
        struct snd_dma_buffer tmpb;
        struct snd_sg_page *table;
        struct page **pgtable;
        int type = SNDRV_DMA_TYPE_DEV;
        pgprot_t prot = PAGE_KERNEL;
        void *area;

        dmab->private_data = sgbuf = kzalloc(sizeof(*sgbuf), GFP_KERNEL);
        if (!sgbuf)
                return NULL;
        if (dmab->dev.type == SNDRV_DMA_TYPE_DEV_WC_SG) {
                type = SNDRV_DMA_TYPE_DEV_WC;
#ifdef pgprot_noncached
                prot = pgprot_noncached(PAGE_KERNEL);
#endif
        }
        sgbuf->dev = dmab->dev.dev;
        pages = snd_sgbuf_aligned_pages(size);
        sgbuf->tblsize = sgbuf_align_table(pages);
        table = kcalloc(sgbuf->tblsize, sizeof(*table), GFP_KERNEL);
        if (!table)
                goto _failed;
        sgbuf->table = table;
        pgtable = kcalloc(sgbuf->tblsize, sizeof(*pgtable), GFP_KERNEL);
        if (!pgtable)
                goto _failed;
        sgbuf->page_table = pgtable;

        /* allocate pages */
        maxpages = MAX_ALLOC_PAGES;
        while (pages > 0) {
                chunk = pages;
                /* don't be too eager to take a huge chunk */
                if (chunk > maxpages)
                        chunk = maxpages;
                chunk <<= PAGE_SHIFT;
                if (snd_dma_alloc_pages_fallback(type, dmab->dev.dev,
                                                 chunk, &tmpb) < 0) {
                        if (!sgbuf->pages)
                                goto _failed;
                        size = sgbuf->pages * PAGE_SIZE;
                        break;
                }
                chunk = tmpb.bytes >> PAGE_SHIFT;
                for (i = 0; i < chunk; i++) {
                        table->buf = tmpb.area;
                        table->addr = tmpb.addr;
                        if (!i)
                                table->addr |= chunk; /* mark head */
                        table++;
                        *pgtable++ = virt_to_page(tmpb.area);
                        tmpb.area += PAGE_SIZE;
                        tmpb.addr += PAGE_SIZE;
                }
                sgbuf->pages += chunk;
                pages -= chunk;
                if (chunk < maxpages)
                        maxpages = chunk;
        }

        sgbuf->size = size;
        area = vmap(sgbuf->page_table, sgbuf->pages, VM_MAP, prot);
        if (!area)
                goto _failed;
        return area;

 _failed:
        snd_dma_sg_free(dmab); /* free the table */
        return NULL;
}

static dma_addr_t snd_dma_sg_get_addr(struct snd_dma_buffer *dmab,
                                      size_t offset)
{
        struct snd_sg_buf *sgbuf = dmab->private_data;
        dma_addr_t addr;

        addr = sgbuf->table[offset >> PAGE_SHIFT].addr;
        addr &= ~((dma_addr_t)PAGE_SIZE - 1);
        return addr + offset % PAGE_SIZE;
}

static struct page *snd_dma_sg_get_page(struct snd_dma_buffer *dmab,
                                        size_t offset)
{
        struct snd_sg_buf *sgbuf = dmab->private_data;
        unsigned int idx = offset >> PAGE_SHIFT;

        if (idx >= (unsigned int)sgbuf->pages)
                return NULL;
        return sgbuf->page_table[idx];
}

static unsigned int snd_dma_sg_get_chunk_size(struct snd_dma_buffer *dmab,
                                              unsigned int ofs,
                                              unsigned int size)
{
        struct snd_sg_buf *sg = dmab->private_data;
        unsigned int start, end, pg;

        start = ofs >> PAGE_SHIFT;
        end = (ofs + size - 1) >> PAGE_SHIFT;
        /* check page continuity */
        pg = sg->table[start].addr >> PAGE_SHIFT;
        for (;;) {
                start++;
                if (start > end)
                        break;
                pg++;
                if ((sg->table[start].addr >> PAGE_SHIFT) != pg)
                        return (start << PAGE_SHIFT) - ofs;
        }
        /* ok, all on continuous pages */
        return size;
}

static int snd_dma_sg_mmap(struct snd_dma_buffer *dmab,
                           struct vm_area_struct *area)
{
        if (dmab->dev.type == SNDRV_DMA_TYPE_DEV_WC_SG)
                area->vm_page_prot = pgprot_writecombine(area->vm_page_prot);
        return -ENOENT; /* continue with the default mmap handler */
}

const struct snd_malloc_ops snd_dma_sg_ops = {
        .alloc = snd_dma_sg_alloc,
        .free = snd_dma_sg_free,
        .get_addr = snd_dma_sg_get_addr,
        .get_page = snd_dma_sg_get_page,
        .get_chunk_size = snd_dma_sg_get_chunk_size,
        .mmap = snd_dma_sg_mmap,
};