ALSA on MIPS platform

[Songmao Tian <tiansm@xxxxxxxxxx>]

Hi,
   In 
http://www.linux-mips.org/archives/linux-mips/2007-04/msg00114.html, 
Atsushi Nemoto pointed out the problem is discussed before, the thread 
can be found at http://lkml.org/lkml/2006/1/25/117. Thanks Atsushi Nemoto:)
   The problem is clear:
1. dma_alloc_noncoherent() return a non-cached address, and 
virt_to_page() need a cached logical addr (Have I named it right?)
2. mmaped dam buffer should be non-cached.

We have a ugly patch, but we want to solve the problem cleanly, so can 
anyone show me the way?

Regards,
Tian

diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index 59b29cd..fd0aa66 100644
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -3138,7 +3138,11 @@ static struct page 
*snd_pcm_mmap_data_nopage(struct vm_area_struct *area,
            return NOPAGE_OOM; /* XXX: is this really due to OOM? */
    } else {
        vaddr = runtime->dma_area + offset;
+#if defined(__mips__) && defined(CONFIG_DMA_NONCOHERENT)
+        page = virt_to_page(CAC_ADDR(vaddr));
+#else
        page = virt_to_page(vaddr);
+#endif
    }
    get_page(page);
    if (type)
@@ -3254,6 +3258,11 @@ static int snd_pcm_mmap(struct file *file, struct 
vm_area_struct *area)
    substream = pcm_file->substream;
    snd_assert(substream != NULL, return -ENXIO);

+#if defined(__mips__) && defined(CONFIG_DMA_NONCOHERENT)
+    /* all mmap using uncached mode */
+    area->vm_page_prot = pgprot_noncached(area->vm_page_prot);
+#endif
+
    offset = area->vm_pgoff << PAGE_SHIFT;
    switch (offset) {
    case SNDRV_PCM_MMAP_OFFSET_STATUS:
diff --git a/sound/core/sgbuf.c b/sound/core/sgbuf.c
index cefd228..2251e70 100644
--- a/sound/core/sgbuf.c
+++ b/sound/core/sgbuf.c
@@ -91,12 +91,21 @@ void *snd_malloc_sgbuf_pages(struct device *device,
        }
        sgbuf->table[i].buf = tmpb.area;
        sgbuf->table[i].addr = tmpb.addr;
+#if defined(__mips__) && defined(CONFIG_DMA_NONCOHERENT)
+        sgbuf->page_table[i] = virt_to_page(CAC_ADDR(tmpb.area));
+#else
        sgbuf->page_table[i] = virt_to_page(tmpb.area);
+#endif
        sgbuf->pages++;
    }

    sgbuf->size = size;
+#if defined(__mips__) && defined(CONFIG_DMA_NONCOHERENT)
+    /* maybe we should use uncached accelerated mode */
+    dmab->area = vmap(sgbuf->page_table, sgbuf->pages, VM_MAP, 
pgprot_noncached(PAGE_KERNEL));
+#else
    dmab->area = vmap(sgbuf->page_table, sgbuf->pages, VM_MAP, 
PAGE_KERNEL);
+#endif
    if (! dmab->area)
        goto _failed;
    return dmab->area;