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

Lars-Peter Clausen
2012-06-29T16:03:06Z

On 06/29/2012 05:04 PM, Laxman Dewangan wrote:
> [...]
>
>
>> +/* 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);
>
> This does not get compiled in ARM because dma_alloc_coherant is macro
> defined as
>
> #define dma_alloc_coherent(d, s, h, f) dma_alloc_attrs(d, s, h, f, NULL)
>
> static inline void *dma_alloc_attrs(struct device *dev, size_t size,
> dma_addr_t *dma_handle, gfp_t flag,
> struct dma_attrs *attrs)
>
>
> I fixed this by
> 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);
> }
>
> /* 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);
> }

I think all dma_alloc_* functions use dma_alloc_attrs internally these days.
I think it might be a better idea just to use dma_alloc_attrs in
__snd_malloc_dev_pages and just pass a dma_attrs struct instead of a function.

Something like:

static void *__snd_malloc_dev_pages(struct device *dev, size_t size,
dma_addr_t *dma, struct dma_attrs *attrs)
{
....
res = dma_alloc_attrs(dev, PAGE_SIZE << pg, dma, gfp_flags, attrs);
....
}

static void *snd_malloc_dev_pages(struct device *dev, size_t size,
dma_addr_t *dma)
{
return __snd_malloc_dev_pages(dev, size, dma, NULL);
}

static void *snd_malloc_dev_wc_pages(struct device *dev, size_t size,
dma_addr_t *dma)
{
DEFINE_DMA_ATTRS(attrs);
dma_set_attr(DMA_ATTR_WRITE_COMBINE, &attrs);

return __snd_malloc_dev_pages(dev, size, dma, &attrs);
}

Same applies for freeing the memory again.

- Lars