Re: [PATCH v7] ALSA: Add SoC on-chip internal ram support for DMA buffer allocation

[Lars-Peter Clausen <lars@metafoo.de>]

On 10/23/2013 05:47 AM, Nicolin Chen wrote:
> Now it's quite common that an SoC contains its on-chip internal RAM.
> By using this RAM space for DMA buffer during audio playback/record,
> we can shutdown the voltage for external RAM to save power.
> 
> So add new DEV type with iram malloc()/free() and accordingly modify
> current default mmap() for the iram circumstance.
> 
> Signed-off-by: Nicolin Chen <b42378@freescale.com>

Looks good to me.

Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>

> ---
> Changelog
> v6->v7:
>  * Assigned pool to private_data field and accordingly refined helper functions.
> v5->v6:
>  * Dropped remaining OF dependency bacause no need to add them:
>    of_node doesn't care about OF; of_get_named_gen_pool() returns NULL if !OF.
> v4->v5:
>  * Minimized the OF dependency.
> v3->v4:
>  * Appropriately placed '#ifdef CONFIG_OF'
>  * Tested by adding '#undef CONFIG_OF' to modified files, and passed compiling.
> v2->v3:
>  * Moved iram specific mmap procedure out of ifdef ARCH_HAS_DMA_MMAP_COHERENT
> v1->v2:
>  * Added of_node check
>  * Dropped noops and unused physical addr in snd_free_dev_iram()
> 
> ---
>  include/sound/memalloc.h |  1 +
>  sound/core/memalloc.c    | 52 ++++++++++++++++++++++++++++++++++++++++++++++++
>  sound/core/pcm_native.c  |  6 ++++++
>  3 files changed, 59 insertions(+)
> 
> diff --git a/include/sound/memalloc.h b/include/sound/memalloc.h
> index cf15b82..510aec4 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_IRAM		4	/* generic device iram-buffer */
>  
>  /*
>   * info for buffer allocation
> diff --git a/sound/core/memalloc.c b/sound/core/memalloc.c
> index bdf826f..18c1d47 100644
> --- a/sound/core/memalloc.c
> +++ b/sound/core/memalloc.c
> @@ -30,6 +30,7 @@
>  #include <linux/seq_file.h>
>  #include <asm/uaccess.h>
>  #include <linux/dma-mapping.h>
> +#include <linux/genalloc.h>
>  #include <linux/moduleparam.h>
>  #include <linux/mutex.h>
>  #include <sound/memalloc.h>
> @@ -157,6 +158,46 @@ static void snd_free_dev_pages(struct device *dev, size_t size, void *ptr,
>  	dec_snd_pages(pg);
>  	dma_free_coherent(dev, PAGE_SIZE << pg, ptr, dma);
>  }
> +
> +/**
> + * snd_malloc_dev_iram - allocate memory from on-chip internal ram
> + * @dmab: buffer allocation record to store the allocated data
> + * @size: number of bytes to allocate from the iram
> + *
> + * This function requires iram phandle provided via of_node
> + */
> +void snd_malloc_dev_iram(struct snd_dma_buffer *dmab, size_t size)
> +{
> +	struct device *dev = dmab->dev.dev;
> +	struct gen_pool *pool = NULL;
> +
> +	if (dev->of_node)
> +		pool = of_get_named_gen_pool(dev->of_node, "iram", 0);
> +
> +	if (!pool)
> +		return;
> +
> +	/* Assign the pool into private_data field */
> +	dmab->private_data = pool;
> +
> +	dmab->area = (void *)gen_pool_alloc(pool, size);
> +	if (!dmab->area)
> +		return;
> +
> +	dmab->addr = gen_pool_virt_to_phys(pool, (unsigned long)dmab->area);
> +}
> +
> +/**
> + * snd_free_dev_iram - free allocated specific memory from on-chip internal ram
> + * @dmab: buffer allocation record to store the allocated data
> + */
> +void snd_free_dev_iram(struct snd_dma_buffer *dmab)
> +{
> +	struct gen_pool *pool = dmab->private_data;
> +
> +	if (pool && dmab->area)
> +		gen_pool_free(pool, (unsigned long)dmab->area, dmab->bytes);
> +}
>  #endif /* CONFIG_HAS_DMA */
>  
>  /*
> @@ -197,6 +238,14 @@ int snd_dma_alloc_pages(int type, struct device *device, size_t size,
>  		dmab->addr = 0;
>  		break;
>  #ifdef CONFIG_HAS_DMA
> +	case SNDRV_DMA_TYPE_DEV_IRAM:
> +		snd_malloc_dev_iram(dmab, size);
> +		if (dmab->area)
> +			break;
> +		/* Internal memory might have limited size and no enough space,
> +		 * so if we fail to malloc, try to fetch memory traditionally.
> +		 */
> +		dmab->dev.type = SNDRV_DMA_TYPE_DEV;
>  	case SNDRV_DMA_TYPE_DEV:
>  		dmab->area = snd_malloc_dev_pages(device, size, &dmab->addr);
>  		break;
> @@ -269,6 +318,9 @@ void snd_dma_free_pages(struct snd_dma_buffer *dmab)
>  		snd_free_pages(dmab->area, dmab->bytes);
>  		break;
>  #ifdef CONFIG_HAS_DMA
> +	case SNDRV_DMA_TYPE_DEV_IRAM:
> +		snd_free_dev_iram(dmab);
> +		break;
>  	case SNDRV_DMA_TYPE_DEV:
>  		snd_free_dev_pages(dmab->dev.dev, dmab->bytes, dmab->area, dmab->addr);
>  		break;
> diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
> index a68d4c6..513f095 100644
> --- a/sound/core/pcm_native.c
> +++ b/sound/core/pcm_native.c
> @@ -3199,6 +3199,12 @@ int snd_pcm_lib_default_mmap(struct snd_pcm_substream *substream,
>  			     struct vm_area_struct *area)
>  {
>  	area->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
> +	if (substream->dma_buffer.dev.type == SNDRV_DMA_TYPE_DEV_IRAM) {
> +		area->vm_page_prot = pgprot_writecombine(area->vm_page_prot);
> +		return remap_pfn_range(area, area->vm_start,
> +				substream->dma_buffer.addr >> PAGE_SHIFT,
> +				area->vm_end - area->vm_start, area->vm_page_prot);
> +	}
>  #ifdef ARCH_HAS_DMA_MMAP_COHERENT
>  	if (!substream->ops->page &&
>  	    substream->dma_buffer.dev.type == SNDRV_DMA_TYPE_DEV)
>