videobuf-dma-contig.c

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/*
 * helper functions for physically contiguous capture buffers
 *
 * The functions support hardware lacking scatter gather support
 * (i.e. the buffers must be linear in physical memory)
 *
 * Copyright (c) 2008 Magnus Damm
 *
 * Based on videobuf-vmalloc.c,
 * (c) 2007 Mauro Carvalho Chehab, <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/dma-mapping.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <media/videobuf-dma-contig.h>

struct videobuf_dma_contig_memory {
    u32 magic;
    void *vaddr;
    dma_addr_t dma_handle;
    bool cached;
    unsigned long size;
};

#define MAGIC_DC_MEM 0x0733ac61
#define MAGIC_CHECK(is, should)                         \
    if (unlikely((is) != (should))) {                   \
        pr_err("magic mismatch: %x expected %x\n", (is), (should)); \
        BUG();                              \
    }

static int __videobuf_dc_alloc(struct device *dev,
                   struct videobuf_dma_contig_memory *mem,
                   unsigned long size, gfp_t flags)
{
    mem->size = size;
    if (mem->cached) {
        mem->vaddr = alloc_pages_exact(mem->size, flags | GFP_DMA);
        if (mem->vaddr) {
            int err;

            mem->dma_handle = dma_map_single(dev, mem->vaddr,
                             mem->size,
                             DMA_FROM_DEVICE);
            err = dma_mapping_error(dev, mem->dma_handle);
            if (err) {
                dev_err(dev, "dma_map_single failed\n");

                free_pages_exact(mem->vaddr, mem->size);
                mem->vaddr = NULL;
                return err;
            }
        }
    } else
        mem->vaddr = dma_alloc_coherent(dev, mem->size,
                        &mem->dma_handle, flags);

    if (!mem->vaddr) {
        dev_err(dev, "memory alloc size %ld failed\n", mem->size);
        return -ENOMEM;
    }

    dev_dbg(dev, "dma mapped data is at %p (%ld)\n", mem->vaddr, mem->size);

    return 0;
}

static void __videobuf_dc_free(struct device *dev,
                   struct videobuf_dma_contig_memory *mem)
{
    if (mem->cached) {
        if (!mem->vaddr)
            return;
        dma_unmap_single(dev, mem->dma_handle, mem->size,
                 DMA_FROM_DEVICE);
        free_pages_exact(mem->vaddr, mem->size);
    } else
        dma_free_coherent(dev, mem->size, mem->vaddr, mem->dma_handle);

    mem->vaddr = NULL;
}

static void videobuf_vm_open(struct vm_area_struct *vma)
{
    struct videobuf_mapping *map = vma->vm_private_data;

    dev_dbg(map->q->dev, "vm_open %p [count=%u,vma=%08lx-%08lx]\n",
        map, map->count, vma->vm_start, vma->vm_end);

    map->count++;
}

static void videobuf_vm_close(struct vm_area_struct *vma)
{
    struct videobuf_mapping *map = vma->vm_private_data;
    struct videobuf_queue *q = map->q;
    int i;

    dev_dbg(q->dev, "vm_close %p [count=%u,vma=%08lx-%08lx]\n",
        map, map->count, vma->vm_start, vma->vm_end);

    map->count--;
    if (0 == map->count) {
        struct videobuf_dma_contig_memory *mem;

        dev_dbg(q->dev, "munmap %p q=%p\n", map, q);
        videobuf_queue_lock(q);

        /* We need first to cancel streams, before unmapping */
        if (q->streaming)
            videobuf_queue_cancel(q);

        for (i = 0; i < VIDEO_MAX_FRAME; i++) {
            if (NULL == q->bufs[i])
                continue;

            if (q->bufs[i]->map != map)
                continue;

            mem = q->bufs[i]->priv;
            if (mem) {
                /* This callback is called only if kernel has
                   allocated memory and this memory is mmapped.
                   In this case, memory should be freed,
                   in order to do memory unmap.
                 */

                MAGIC_CHECK(mem->magic, MAGIC_DC_MEM);

                /* vfree is not atomic - can't be
                   called with IRQ's disabled
                 */
                dev_dbg(q->dev, "buf[%d] freeing %p\n",
                    i, mem->vaddr);

                __videobuf_dc_free(q->dev, mem);
                mem->vaddr = NULL;
            }

            q->bufs[i]->map = NULL;
            q->bufs[i]->baddr = 0;
        }

        kfree(map);

        videobuf_queue_unlock(q);
    }
}

static const struct vm_operations_struct videobuf_vm_ops = {
    .open   = videobuf_vm_open,
    .close  = videobuf_vm_close,
};

static void videobuf_dma_contig_user_put(struct videobuf_dma_contig_memory *mem)
{
    mem->dma_handle = 0;
    mem->size = 0;
}

static int videobuf_dma_contig_user_get(struct videobuf_dma_contig_memory *mem,
                    struct videobuf_buffer *vb)
{
    struct mm_struct *mm = current->mm;
    struct vm_area_struct *vma;
    unsigned long prev_pfn, this_pfn;
    unsigned long pages_done, user_address;
    unsigned int offset;
    int ret;

    offset = vb->baddr & ~PAGE_MASK;
    mem->size = PAGE_ALIGN(vb->size + offset);
    ret = -EINVAL;

    down_read(&mm->mmap_sem);

    vma = find_vma(mm, vb->baddr);
    if (!vma)
        goto out_up;

    if ((vb->baddr + mem->size) > vma->vm_end)
        goto out_up;

    pages_done = 0;
    prev_pfn = 0; /* kill warning */
    user_address = vb->baddr;

    while (pages_done < (mem->size >> PAGE_SHIFT)) {
        ret = follow_pfn(vma, user_address, &this_pfn);
        if (ret)
            break;

        if (pages_done == 0)
            mem->dma_handle = (this_pfn << PAGE_SHIFT) + offset;
        else if (this_pfn != (prev_pfn + 1))
            ret = -EFAULT;

        if (ret)
            break;

        prev_pfn = this_pfn;
        user_address += PAGE_SIZE;
        pages_done++;
    }

out_up:
    up_read(&current->mm->mmap_sem);

    return ret;
}

static struct videobuf_buffer *__videobuf_alloc_vb(size_t size, bool cached)
{
    struct videobuf_dma_contig_memory *mem;
    struct videobuf_buffer *vb;

    vb = kzalloc(size + sizeof(*mem), GFP_KERNEL);
    if (vb) {
        vb->priv = ((char *)vb) + size;
        mem = vb->priv;
        mem->magic = MAGIC_DC_MEM;
        mem->cached = cached;
    }

    return vb;
}

static struct videobuf_buffer *__videobuf_alloc_uncached(size_t size)
{
    return __videobuf_alloc_vb(size, false);
}

static struct videobuf_buffer *__videobuf_alloc_cached(size_t size)
{
    return __videobuf_alloc_vb(size, true);
}

static void *__videobuf_to_vaddr(struct videobuf_buffer *buf)
{
    struct videobuf_dma_contig_memory *mem = buf->priv;

    BUG_ON(!mem);
    MAGIC_CHECK(mem->magic, MAGIC_DC_MEM);

    return mem->vaddr;
}

static int __videobuf_iolock(struct videobuf_queue *q,
                 struct videobuf_buffer *vb,
                 struct v4l2_framebuffer *fbuf)
{
    struct videobuf_dma_contig_memory *mem = vb->priv;

    BUG_ON(!mem);
    MAGIC_CHECK(mem->magic, MAGIC_DC_MEM);

    switch (vb->memory) {
    case V4L2_MEMORY_MMAP:
        dev_dbg(q->dev, "%s memory method MMAP\n", __func__);

        /* All handling should be done by __videobuf_mmap_mapper() */
        if (!mem->vaddr) {
            dev_err(q->dev, "memory is not alloced/mmapped.\n");
            return -EINVAL;
        }
        break;
    case V4L2_MEMORY_USERPTR:
        dev_dbg(q->dev, "%s memory method USERPTR\n", __func__);

        /* handle pointer from user space */
        if (vb->baddr)
            return videobuf_dma_contig_user_get(mem, vb);

        /* allocate memory for the read() method */
        if (__videobuf_dc_alloc(q->dev, mem, PAGE_ALIGN(vb->size),
                    GFP_KERNEL))
            return -ENOMEM;
        break;
    case V4L2_MEMORY_OVERLAY:
    default:
        dev_dbg(q->dev, "%s memory method OVERLAY/unknown\n", __func__);
        return -EINVAL;
    }

    return 0;
}

static int __videobuf_sync(struct videobuf_queue *q,
               struct videobuf_buffer *buf)
{
    struct videobuf_dma_contig_memory *mem = buf->priv;
    BUG_ON(!mem);
    MAGIC_CHECK(mem->magic, MAGIC_DC_MEM);

    dma_sync_single_for_cpu(q->dev, mem->dma_handle, mem->size,
                DMA_FROM_DEVICE);

    return 0;
}

static int __videobuf_mmap_mapper(struct videobuf_queue *q,
                  struct videobuf_buffer *buf,
                  struct vm_area_struct *vma)
{
    struct videobuf_dma_contig_memory *mem;
    struct videobuf_mapping *map;
    int retval;
    unsigned long size;
    unsigned long pos, start = vma->vm_start;
    struct page *page;

    dev_dbg(q->dev, "%s\n", __func__);

    /* create mapping + update buffer list */
    map = kzalloc(sizeof(struct videobuf_mapping), GFP_KERNEL);
    if (!map)
        return -ENOMEM;

    buf->map = map;
    map->q = q;

    buf->baddr = vma->vm_start;

    mem = buf->priv;
    BUG_ON(!mem);
    MAGIC_CHECK(mem->magic, MAGIC_DC_MEM);

    if (__videobuf_dc_alloc(q->dev, mem, PAGE_ALIGN(buf->bsize),
                GFP_KERNEL | __GFP_COMP))
        goto error;

    /* Try to remap memory */

    size = vma->vm_end - vma->vm_start;
    size = (size < mem->size) ? size : mem->size;

    if (!mem->cached) {
        vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
        retval = remap_pfn_range(vma, vma->vm_start,
             mem->dma_handle >> PAGE_SHIFT,
                 size, vma->vm_page_prot);
        if (retval) {
            dev_err(q->dev, "mmap: remap failed with error %d. ",
                                retval);
            dma_free_coherent(q->dev, mem->size,
                    mem->vaddr, mem->dma_handle);
            goto error;
        }
    } else {
        pos = (unsigned long)mem->vaddr;

        while (size > 0) {
            page = virt_to_page((void *)pos);
            if (NULL == page) {
                dev_err(q->dev, "mmap: virt_to_page failed\n");
                __videobuf_dc_free(q->dev, mem);
                goto error;
            }
            retval = vm_insert_page(vma, start, page);
            if (retval) {
                dev_err(q->dev, "mmap: insert failed with error %d\n",
                    retval);
                __videobuf_dc_free(q->dev, mem);
                goto error;
            }
            start += PAGE_SIZE;
            pos += PAGE_SIZE;

            if (size > PAGE_SIZE)
                size -= PAGE_SIZE;
            else
                size = 0;
        }
    }

    vma->vm_ops = &videobuf_vm_ops;
    vma->vm_flags |= VM_DONTEXPAND;
    vma->vm_private_data = map;

    dev_dbg(q->dev, "mmap %p: q=%p %08lx-%08lx (%lx) pgoff %08lx buf %d\n",
        map, q, vma->vm_start, vma->vm_end,
        (long int)buf->bsize, vma->vm_pgoff, buf->i);

    videobuf_vm_open(vma);

    return 0;

error:
    kfree(map);
    return -ENOMEM;
}

static struct videobuf_qtype_ops qops = {
    .magic      = MAGIC_QTYPE_OPS,
    .alloc_vb   = __videobuf_alloc_uncached,
    .iolock     = __videobuf_iolock,
    .mmap_mapper    = __videobuf_mmap_mapper,
    .vaddr      = __videobuf_to_vaddr,
};

static struct videobuf_qtype_ops qops_cached = {
    .magic      = MAGIC_QTYPE_OPS,
    .alloc_vb   = __videobuf_alloc_cached,
    .iolock     = __videobuf_iolock,
    .sync       = __videobuf_sync,
    .mmap_mapper    = __videobuf_mmap_mapper,
    .vaddr      = __videobuf_to_vaddr,
};

void videobuf_queue_dma_contig_init(struct videobuf_queue *q,
                    const struct videobuf_queue_ops *ops,
                    struct device *dev,
                    spinlock_t *irqlock,
                    enum v4l2_buf_type type,
                    enum v4l2_field field,
                    unsigned int msize,
                    void *priv,
                    struct mutex *ext_lock)
{
    videobuf_queue_core_init(q, ops, dev, irqlock, type, field, msize,
                 priv, &qops, ext_lock);
}
EXPORT_SYMBOL_GPL(videobuf_queue_dma_contig_init);

void videobuf_queue_dma_contig_init_cached(struct videobuf_queue *q,
                       const struct videobuf_queue_ops *ops,
                       struct device *dev,
                       spinlock_t *irqlock,
                       enum v4l2_buf_type type,
                       enum v4l2_field field,
                       unsigned int msize,
                       void *priv, struct mutex *ext_lock)
{
    videobuf_queue_core_init(q, ops, dev, irqlock, type, field, msize,
                 priv, &qops_cached, ext_lock);
}
EXPORT_SYMBOL_GPL(videobuf_queue_dma_contig_init_cached);

dma_addr_t videobuf_to_dma_contig(struct videobuf_buffer *buf)
{
    struct videobuf_dma_contig_memory *mem = buf->priv;

    BUG_ON(!mem);
    MAGIC_CHECK(mem->magic, MAGIC_DC_MEM);

    return mem->dma_handle;
}
EXPORT_SYMBOL_GPL(videobuf_to_dma_contig);

void videobuf_dma_contig_free(struct videobuf_queue *q,
                  struct videobuf_buffer *buf)
{
    struct videobuf_dma_contig_memory *mem = buf->priv;

    /* mmapped memory can't be freed here, otherwise mmapped region
       would be released, while still needed. In this case, the memory
       release should happen inside videobuf_vm_close().
       So, it should free memory only if the memory were allocated for
       read() operation.
     */
    if (buf->memory != V4L2_MEMORY_USERPTR)
        return;

    if (!mem)
        return;

    MAGIC_CHECK(mem->magic, MAGIC_DC_MEM);

    /* handle user space pointer case */
    if (buf->baddr) {
        videobuf_dma_contig_user_put(mem);
        return;
    }

    /* read() method */
    if (mem->vaddr) {
        __videobuf_dc_free(q->dev, mem);
        mem->vaddr = NULL;
    }
}
EXPORT_SYMBOL_GPL(videobuf_dma_contig_free);

MODULE_DESCRIPTION("helper module to manage video4linux dma contig buffers");
MODULE_AUTHOR("Magnus Damm");
MODULE_LICENSE("GPL");