[alsa-devel] 答复: A bug about cache inconsistency report

[Hans Hu(SH-RD)]

> >Then the next step would be to fake sg-buffer from this straight
> >buffer.  Revert the above, and modify sgbuf.c to the following:
> >- Allocate a large continuous buffer
> >- Assign each page in this large buffer
>
> >If this still works, it's not about vmap, but it just means that the
> >physically ordered pages do matter -- implicitly showing that the
> >snooping behavior isn't properly turned on / off on the controller.
>
> To fake SG-buffer, I did this test: restore all the codes to the original, then added some codes in snd_malloc_sgbuf_pages() like below, the result is badly niose.

>Not really what I meant.  Rather something like below (totally untested).

[Hans :] I know what you mean now and complete code like below, but the result is still noise.


Thanks,

Hans
---

diff --git a/sound/core/sgbuf.c b/sound/core/sgbuf.c index 84fffabdd129..643f6cb2048c 100644
--- a/sound/core/sgbuf.c
+++ b/sound/core/sgbuf.c
@@ -68,7 +68,7 @@ void *snd_malloc_sgbuf_pages(struct device *device,
      size_t *res_size)
 {
 struct snd_sg_buf *sgbuf;
-unsigned int i, pages, chunk, maxpages;
+unsigned int i, pages, chunk;
 struct snd_dma_buffer tmpb;
 struct snd_sg_page *table;
 struct page **pgtable;
@@ -90,38 +90,18 @@ void *snd_malloc_sgbuf_pages(struct device *device,
 goto _failed;
 sgbuf->page_table = pgtable;

-/* allocate pages */
-maxpages = MAX_ALLOC_PAGES;
-while (pages > 0) {
-chunk = pages;
-/* don't be too eager to take a huge chunk */
-if (chunk > maxpages)
-chunk = maxpages;
-chunk <<= PAGE_SHIFT;
-if (snd_dma_alloc_pages_fallback(SNDRV_DMA_TYPE_DEV, device,
- chunk, &tmpb) < 0) {
-if (!sgbuf->pages)
-goto _failed;
-if (!res_size)
-goto _failed;
-size = sgbuf->pages * PAGE_SIZE;
-break;
-}
-chunk = tmpb.bytes >> PAGE_SHIFT;
-for (i = 0; i < chunk; i++) {
-table->buf = tmpb.area;
-table->addr = tmpb.addr;
-if (!i)
-table->addr |= chunk; /* mark head */
-table++;
-*pgtable++ = virt_to_page(tmpb.area);
-tmpb.area += PAGE_SIZE;
-tmpb.addr += PAGE_SIZE;
-}
-sgbuf->pages += chunk;
-pages -= chunk;
-if (chunk < maxpages)
-maxpages = chunk;
+if (snd_dma_alloc_pages(SNDRV_DMA_TYPE_DEV, device, size, &tmpb) < 0)
+goto _failed;
+chunk = tmpb.bytes >> PAGE_SHIFT;
+for (i = 0; i < pages; i++) {
+table->buf = tmpb.area;
+table->addr = tmpb.addr;
+if (!i)
+table->addr |= pages; /* mark head */
+table++;
+*pgtable++ = virt_to_page(tmpb.area);
+tmpb.area += PAGE_SIZE;
+tmpb.addr += PAGE_SIZE;
+sgbuf->pages += chunk;
 }

 sgbuf->size = size;


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