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    Subject[PATCH V2 1/2] ALSA: Support writecombine DMA buffer memory page alloc/free
    Date
    Some of architecture like ARM support the writecombine DMA
    buffer which is used for pcm substream DMA buffer.

    Supporting writecombine DMA buffer allocation/free/mmap
    through the sound library memory management.

    Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
    ---
    Changes from V1:
    Integrate the changes from Takashi's sample code for supporting
    writecombine.

    include/sound/memalloc.h | 1 +
    sound/core/memalloc.c | 74 +++++++++++++++++++++++++++++++++++++++++-----
    sound/core/pcm_native.c | 10 ++++++
    3 files changed, 77 insertions(+), 8 deletions(-)

    diff --git a/include/sound/memalloc.h b/include/sound/memalloc.h
    index c425062..0328e37 100644
    --- a/include/sound/memalloc.h
    +++ b/include/sound/memalloc.h
    @@ -52,6 +52,7 @@ struct snd_dma_device {
    #else
    #define SNDRV_DMA_TYPE_DEV_SG SNDRV_DMA_TYPE_DEV /* no SG-buf support */
    #endif
    +#define SNDRV_DMA_TYPE_DEV_WC 4 /* writecombine page */

    /*
    * info for buffer allocation
    diff --git a/sound/core/memalloc.c b/sound/core/memalloc.c
    index 6915692..7468251 100644
    --- a/sound/core/memalloc.c
    +++ b/sound/core/memalloc.c
    @@ -124,8 +124,10 @@ void snd_free_pages(void *ptr, size_t size)
    */

    #ifdef CONFIG_HAS_DMA
    -/* allocate the coherent DMA pages */
    -static void *snd_malloc_dev_pages(struct device *dev, size_t size, dma_addr_t *dma)
    +static void *_snd_malloc_dev_pages(struct device *dev, size_t size,
    + dma_addr_t *dma,
    + void *(*alloc_func)(struct device *dev, size_t size,
    + dma_addr_t *dma, gfp_t gfp_flags))
    {
    int pg;
    void *res;
    @@ -138,16 +140,18 @@ static void *snd_malloc_dev_pages(struct device *dev, size_t size, dma_addr_t *d
    | __GFP_COMP /* compound page lets parts be mapped */
    | __GFP_NORETRY /* don't trigger OOM-killer */
    | __GFP_NOWARN; /* no stack trace print - this call is non-critical */
    - res = dma_alloc_coherent(dev, PAGE_SIZE << pg, dma, gfp_flags);
    + res = alloc_func(dev, PAGE_SIZE << pg, dma, gfp_flags);
    if (res != NULL)
    inc_snd_pages(pg);

    return res;
    }

    -/* free the coherent DMA pages */
    -static void snd_free_dev_pages(struct device *dev, size_t size, void *ptr,
    - dma_addr_t dma)
    +static void _snd_free_dev_pages(struct device *dev, size_t size, void *ptr,
    + dma_addr_t dma,
    + void (*free_func)(struct device *dev,
    + size_t size, void *vaddr,
    + dma_addr_t dma_handle))
    {
    int pg;

    @@ -155,8 +159,51 @@ static void snd_free_dev_pages(struct device *dev, size_t size, void *ptr,
    return;
    pg = get_order(size);
    dec_snd_pages(pg);
    - dma_free_coherent(dev, PAGE_SIZE << pg, ptr, dma);
    + free_func(dev, PAGE_SIZE << pg, ptr, dma);
    +}
    +
    +static void *_dma_alloc_coherent(struct device *dev, size_t size,
    + dma_addr_t *dma_handle, gfp_t flag)
    +{
    + return dma_alloc_coherent(dev, size, dma_handle, flag);
    +}
    +
    +static void _dma_free_coherent(struct device *dev, size_t size,
    + void *vaddr, dma_addr_t dma_handle)
    +{
    + dma_free_coherent(dev, size, vaddr, dma_handle);
    +}
    +
    +
    +/* allocate the coherent DMA pages */
    +static void *snd_malloc_dev_pages(struct device *dev, size_t size,
    + dma_addr_t *dma)
    +{
    + return _snd_malloc_dev_pages(dev, size, dma, _dma_alloc_coherent);
    +}
    +
    +/* free the coherent DMA pages */
    +static void snd_free_dev_pages(struct device *dev, size_t size, void *ptr,
    + dma_addr_t dma)
    +{
    + _snd_free_dev_pages(dev, size, ptr, dma, _dma_free_coherent);
    }
    +
    +#ifdef CONFIG_ARM
    +/* allocate the writecombine DMA pages */
    +static void *snd_malloc_dev_wc_pages(struct device *dev, size_t size,
    + dma_addr_t *dma)
    +{
    + return _snd_malloc_dev_pages(dev, size, dma, dma_alloc_writecombine);
    +}
    +
    +/* free the writecombine DMA pages */
    +static void snd_free_dev_wc_pages(struct device *dev, size_t size, void *ptr,
    + dma_addr_t dma)
    +{
    + _snd_free_dev_pages(dev, size, ptr, dma, dma_free_writecombine);
    +}
    +#endif
    #endif /* CONFIG_HAS_DMA */

    /*
    @@ -200,6 +247,11 @@ int snd_dma_alloc_pages(int type, struct device *device, size_t size,
    case SNDRV_DMA_TYPE_DEV:
    dmab->area = snd_malloc_dev_pages(device, size, &dmab->addr);
    break;
    +#ifdef CONFIG_ARM
    + case SNDRV_DMA_TYPE_DEV_WC:
    + dmab->area = snd_malloc_dev_wc_pages(device, size, &dmab->addr);
    + break;
    +#endif
    #endif
    #ifdef CONFIG_SND_DMA_SGBUF
    case SNDRV_DMA_TYPE_DEV_SG:
    @@ -272,6 +324,12 @@ void snd_dma_free_pages(struct snd_dma_buffer *dmab)
    case SNDRV_DMA_TYPE_DEV:
    snd_free_dev_pages(dmab->dev.dev, dmab->bytes, dmab->area, dmab->addr);
    break;
    +#ifdef CONFIG_ARM
    + case SNDRV_DMA_TYPE_DEV_WC:
    + snd_free_dev_wc_pages(dmab->dev.dev, dmab->bytes, dmab->area,
    + dmab->addr);
    + break;
    +#endif
    #endif
    #ifdef CONFIG_SND_DMA_SGBUF
    case SNDRV_DMA_TYPE_DEV_SG:
    @@ -378,7 +436,7 @@ static int snd_mem_proc_read(struct seq_file *seq, void *offset)
    long pages = snd_allocated_pages >> (PAGE_SHIFT-12);
    struct snd_mem_list *mem;
    int devno;
    - static char *types[] = { "UNKNOWN", "CONT", "DEV", "DEV-SG" };
    + static char *types[] = { "UNKNOWN", "CONT", "DEV", "DEV-SG" , "WC"};

    mutex_lock(&list_mutex);
    seq_printf(seq, "pages : %li bytes (%li pages per %likB)\n",
    diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
    index 53b5ada..28d949c 100644
    --- a/sound/core/pcm_native.c
    +++ b/sound/core/pcm_native.c
    @@ -3170,6 +3170,16 @@ int snd_pcm_lib_default_mmap(struct snd_pcm_substream *substream,
    struct vm_area_struct *area)
    {
    area->vm_flags |= VM_RESERVED;
    +
    +#ifdef CONFIG_ARM
    + if (substream->dma_buffer.dev.type == SNDRV_DMA_TYPE_DEV_WC)
    + return dma_mmap_writecombine(substream->dma_buffer.dev.dev,
    + area,
    + substream->runtime->dma_area,
    + substream->runtime->dma_addr,
    + area->vm_end - area->vm_start);
    +#endif
    +
    #ifdef ARCH_HAS_DMA_MMAP_COHERENT
    if (!substream->ops->page &&
    substream->dma_buffer.dev.type == SNDRV_DMA_TYPE_DEV)
    --
    1.7.1.1


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