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authorTakashi Iwai <tiwai@suse.de>2008-07-30 15:13:33 +0200
committerJaroslav Kysela <perex@perex.cz>2008-08-25 09:57:38 +0200
commit51e9f2e665bf2b6a01be275d64c336d942c59a66 (patch)
tree75b79c23288a820eea6959e79060e3e4fb9d0eae /sound/core/pcm_memory.c
parent4e184f8fc06411f35fdcf4b9bc6187c857bf7214 (diff)
ALSA: Allocate larger pages in sgbuf
Most hardwares have limited buffer-descriptor table length. This also restricts the max buffer size of the sound driver. For example, snd-hda-intel has 1MB buffer size limit, and this is because it can have at most 256 BDL entries. For supporting larger buffers, we need to allocate larger pages even for sg-buffers. This patch changes the sgbuf allocation code to try to allocate larger pages first. At each head of the allocated pages, the number of allocated pages is stored in the lowest bits of the corresponding entry of the table addr field. This change isn't visible as long as the driver uses snd_sgbuf_get_addr() helper. Also, the patch adds a new function, snd_pcm_sgbuf_get_chunk_size(). This returns the size of the chunk on continuous pages starting at the given position offset. If the chunk reaches to a non-continuous page, it returns the size to the boundary. Signed-off-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Jaroslav Kysela <perex@perex.cz>
Diffstat (limited to 'sound/core/pcm_memory.c')
-rw-r--r--sound/core/pcm_memory.c26
1 files changed, 26 insertions, 0 deletions
diff --git a/sound/core/pcm_memory.c b/sound/core/pcm_memory.c
index 859b1185e69a..a6d42808828c 100644
--- a/sound/core/pcm_memory.c
+++ b/sound/core/pcm_memory.c
@@ -324,6 +324,32 @@ struct page *snd_pcm_sgbuf_ops_page(struct snd_pcm_substream *substream, unsigne
EXPORT_SYMBOL(snd_pcm_sgbuf_ops_page);
+/*
+ * compute the max chunk size with continuous pages on sg-buffer
+ */
+unsigned int snd_pcm_sgbuf_get_chunk_size(struct snd_pcm_substream *substream,
+ unsigned int ofs, unsigned int size)
+{
+ struct snd_sg_buf *sg = snd_pcm_substream_sgbuf(substream);
+ unsigned int start, end, pg;
+
+ start = ofs >> PAGE_SHIFT;
+ end = (ofs + size - 1) >> PAGE_SHIFT;
+ /* check page continuity */
+ pg = sg->table[start].addr >> PAGE_SHIFT;
+ for (;;) {
+ start++;
+ if (start > end)
+ break;
+ pg++;
+ if ((sg->table[start].addr >> PAGE_SHIFT) != pg)
+ return (start << PAGE_SHIFT) - ofs;
+ }
+ /* ok, all on continuous pages */
+ return size;
+}
+EXPORT_SYMBOL(snd_pcm_sgbuf_get_chunk_size);
+
/**
* snd_pcm_lib_malloc_pages - allocate the DMA buffer
* @substream: the substream to allocate the DMA buffer to