Re: [PATCH 0/3] ASoC: Move pcm writecombine dma buffer allocation to core

Takashi Iwai
2012-06-29T12:13:14Z

At Fri, 29 Jun 2012 15:53:15 +0530,
Laxman Dewangan wrote:
>
> Some of the ARM based soc allocate the writecombine dma buffer for
> pcm substreams. They have the same codes for managing this buffer.
> Moving this to the core/pcm files so that they can use that directly.
>
> Remove the code from Tegra PCM and use these new library function.
>
> This is enabled only for ARM specific and can be extended to other
> architecture if they support the writecombine dma buffer.
>
> This patch is based on detail discussion on patch:
> [PATCH] ASoC: snd_dmaengine: add common api for pcm_mmap
> And suggestion from Lars and Takashi.

Looking through your patch, I think an easier integration is just to
add writecombine option to memalloc.c which calls
dma_alloc_writecombine() instead of dma_alloc_coherent().

The addition for mmap is still an open question. Again, an easier
option so far looks like just add the call of dma_alloc_writecombine()
in snd_pcm_lib_default_mmap(). Alternatively, we can create an
individual mmap pcm_ops as we discussed.

Below is a totally untested patch, but you can imagine what I meant.

After this change, replace with snd_pcm_lib_malloc_pages with
SNDRV_DMA_TYPE_DEV_WC, and that's all you need in the driver side.

Takashi

---
diff --git a/include/sound/memalloc.h b/include/sound/memalloc.h
index c425062..7840340 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 pages */

/*
* info for buffer allocation
diff --git a/sound/core/memalloc.c b/sound/core/memalloc.c
index 6915692..11108e8 100644
--- a/sound/core/memalloc.c
+++ b/sound/core/memalloc.c
@@ -124,8 +124,12 @@ 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 *(*func)(struct device *dev,
+ size_t size,
+ dma_addr_t *dma_handle,
+ gfp_t flag))
{
int pg;
void *res;
@@ -138,16 +142,18 @@ 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 = 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 (*func)(struct device *dev,
+ size_t size, void *vaddr,
+ dma_addr_t dma_handle))
{
int pg;

@@ -155,8 +161,36 @@ 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);
+ func(dev, PAGE_SIZE << pg, ptr, dma);
+}
+
+/* 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, 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, ptr, dma, dma_free_writecombine);
+}
+#endif /* CONFIG_ARM */
#endif /* CONFIG_HAS_DMA */

/*
@@ -200,6 +234,11 @@ 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 +311,11 @@ 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 +422,7 @@ 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..c499791 100644
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -3170,6 +3170,14 @@ 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)