PowerPC equivalent to dma_mmap_writecombine()?

I'm porting a driver from ARM to PowerPC, and I came across this function:

static int at91_pcm_mmap(struct snd_pcm_substream *substream,
	struct vm_area_struct *vma)
{
	struct snd_pcm_runtime *runtime = substream->runtime;

	return dma_mmap_writecombine(substream->pcm->card->dev, vma,
				     runtime->dma_area,
				     runtime->dma_addr,
				     runtime->dma_bytes);
}

There are no dma_mmap_x() functions in arch/powerpc.  Can someone tell me what the powerpc 
equivalent to dma_mmap_writecombine() is?

-- 
Timur Tabi
Linux Kernel Developer @ Freescale