ALSA: Fix SG-buffer DMA with non-coherent architectures

Using SG-buffers with dma_alloc_coherent() is often very inefficient
on non-coherent architectures because a tracking record could be
allocated in addition for each dma_alloc_coherent() call.
Instead, simply disable SG-buffers but just allocate normal continuous
buffers on non-supported (currently all but x86) architectures.

Signed-off-by: Takashi Iwai <[e-mail]>

include/sound/memalloc.h

···
 #define SNDRV_DMA_TYPE_UNKNOWN		0	/* not defined */
 #define SNDRV_DMA_TYPE_CONTINUOUS	1	/* continuous no-DMA memory */
 #define SNDRV_DMA_TYPE_DEV		2	/* generic device continuous */
+#ifdef CONFIG_SND_DMA_SGBUF
 #define SNDRV_DMA_TYPE_DEV_SG		3	/* generic device SG-buffer */
+#else
+#define SNDRV_DMA_TYPE_DEV_SG	SNDRV_DMA_TYPE_DEV /* no SG-buf support */
+#endif
 
 /*
  * info for buffer allocation
···
 	void *private_data;	/* private for allocator; don't touch */
 };
 
+#ifdef CONFIG_SND_DMA_SGBUF
 /*
  * Scatter-Gather generic device pages
  */
···
 {
 	return sgbuf->table[offset >> PAGE_SHIFT].buf + offset % PAGE_SIZE;
 }
+#endif /* CONFIG_SND_DMA_SGBUF */
 
 /* allocate/release a buffer */
 int snd_dma_alloc_pages(int type, struct device *dev, size_t size,

include/sound/pcm.h

···
 int snd_pcm_lib_malloc_pages(struct snd_pcm_substream *substream, size_t size);
 int snd_pcm_lib_free_pages(struct snd_pcm_substream *substream);
 
+#ifdef CONFIG_SND_DMA_SGBUF
 /*
  * SG-buffer handling
  */
···
 				    unsigned long offset);
 unsigned int snd_pcm_sgbuf_get_chunk_size(struct snd_pcm_substream *substream,
 					  unsigned int ofs, unsigned int size);
+
+#else /* !SND_DMA_SGBUF */
+/*
+ * fake using a continuous buffer
+ */
+static inline dma_addr_t
+snd_pcm_sgbuf_get_addr(struct snd_pcm_substream *substream, unsigned int ofs)
+{
+	return substream->runtime->dma_addr + ofs;
+}
+
+static inline void *
+snd_pcm_sgbuf_get_ptr(struct snd_pcm_substream *substream, unsigned int ofs)
+{
+	return substream->runtime->dma_area + ofs;
+}
+
+#define snd_pcm_sgbuf_ops_page	NULL
+
+#define snd_pcm_sgbuf_get_chunk_size(subs, ofs, size)	(size)
+
+#endif /* SND_DMA_SGBUF */
 
 /* handle mmap counter - PCM mmap callback should handle this counter properly */
 static inline void snd_pcm_mmap_data_open(struct vm_area_struct *area)

sound/core/Kconfig

···
 config SND_VMASTER
 	bool
 
+config SND_DMA_SGBUF
+	def_bool y
+	depends on X86
+
 source "sound/core/seq/Kconfig"

sound/core/Makefile

···
 		pcm_memory.o
 
 snd-page-alloc-y := memalloc.o
-snd-page-alloc-$(CONFIG_HAS_DMA) += sgbuf.o
+snd-page-alloc-$(CONFIG_SND_DMA_SGBUF) += sgbuf.o
 
 snd-rawmidi-objs  := rawmidi.o
 snd-timer-objs    := timer.o

sound/core/memalloc.c

···
 	case SNDRV_DMA_TYPE_DEV:
 		dmab->area = snd_malloc_dev_pages(device, size, &dmab->addr);
 		break;
+#endif
+#ifdef CONFIG_SND_DMA_SGBUF
 	case SNDRV_DMA_TYPE_DEV_SG:
 		snd_malloc_sgbuf_pages(device, size, dmab, NULL);
 		break;
···
 	case SNDRV_DMA_TYPE_DEV:
 		snd_free_dev_pages(dmab->dev.dev, dmab->bytes, dmab->area, dmab->addr);
 		break;
+#endif
+#ifdef CONFIG_SND_DMA_SGBUF
 	case SNDRV_DMA_TYPE_DEV_SG:
 		snd_free_sgbuf_pages(dmab);
 		break;

sound/core/pcm_memory.c

···
 
 EXPORT_SYMBOL(snd_pcm_lib_preallocate_pages_for_all);
 
+#ifdef CONFIG_SND_DMA_SGBUF
 /**
  * snd_pcm_sgbuf_ops_page - get the page struct at the given offset
  * @substream: the pcm substream instance
···
 	return size;
 }
 EXPORT_SYMBOL(snd_pcm_sgbuf_get_chunk_size);
+#endif /* CONFIG_SND_DMA_SGBUF */
 
 /**
  * snd_pcm_lib_malloc_pages - allocate the DMA buffer