At Fri, 03 Aug 2007 23:57:07 +0800, Songmao Tian wrote:
Takashi Iwai wrote:
At Fri, 03 Aug 2007 21:50:36 +0800, Songmao Tian wrote:
Atsushi Nemoto wrote:
On Wed, 01 Aug 2007 15:56:48 +0800, Songmao Tian tiansm@lemote.com wrote:
The problem is clear:
- 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?
virt_to_page() is used in many place in mm so making it robust might affect performance. IMHO virt_to_page() seems too low-level as DMA API.
If something like dma_virt_to_page(dev, cpu_addr) which can take a cpu address returned by dma_xxx APIs was defined, MIPS can implement it appropriately.
And then pgprot_noncached issues still exist...
Atsushi Nemoto
I agree, and I am investigating to implement a dma_map_coherent, but It seems dma_map_coherent doesn't solve all the problem and will change a lot of code:(
It won't be that much. You'll need to change snd_pcm_default_mmap() in sound/core/pcm_native.c to call dma_mmap_coherent() directly instead of nopage ops. But, this won't work with SG-buffers, which requires some more additional works.
Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@alsa-project.org http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
I have no idea if the patch can work, the idea is not very clear now. And I use vt686b ac97 sound driver, the driver use sgbuf, so I will write a test program tomorrow. Good sleep...:)
Ah, that's a bad luck. Then your patch won't work as it is. We'll need another function for SG-buffer, that calls dma_mmap_coherent() for each page found in the given buffer.
Takashi
And if any of you can take some time look into the patch, and give some review will be appreciated:)
diff --git a/arch/mips/mm/dma-default.c b/arch/mips/mm/dma-default.c index 76903c7..f088a6b 100644 --- a/arch/mips/mm/dma-default.c +++ b/arch/mips/mm/dma-default.c @@ -369,3 +369,23 @@ void dma_cache_sync(struct device *dev, void *vaddr, size_t size, }
EXPORT_SYMBOL(dma_cache_sync);
+static int dma_mmap(struct device *dev, struct vm_area_struct *vma,
void *cpu_addr, dma_addr_t dma_addr, size_t size)+{
- if (remap_pfn_range(vma, vma->vm_start,
PFN_DOWN(virt_to_phys(CAC_ADDR(cpu_addr))) +vma->vm_pgoff,
vma->vm_end - vma->vm_start,vma->vm_page_prot))return -EAGAIN;- return 0;
+}
+int dma_mmap_coherent(struct device *dev, struct vm_area_struct *vma,
void *cpu_addr, dma_addr_t dma_addr, size_t size)+{
- vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
- return dma_mmap(dev, vma, cpu_addr, dma_addr, size);
+} +EXPORT_SYMBOL(dma_mmap_coherent);
diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index 59b29cd..af82a3b 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -3152,6 +3152,8 @@ static struct vm_operations_struct snd_pcm_vm_ops_data = .close = snd_pcm_mmap_data_close, .nopage = snd_pcm_mmap_data_nopage, }; +int dma_mmap_coherent(struct device *dev, struct vm_area_struct *vma,
void *cpu_addr, dma_addr_t dma_addr, size_t size);/*
- mmap the DMA buffer on RAM
@@ -3159,9 +3161,10 @@ static struct vm_operations_struct snd_pcm_vm_ops_data = static int snd_pcm_default_mmap(struct snd_pcm_substream *substream, struct vm_area_struct *area) {
- area->vm_ops = &snd_pcm_vm_ops_data;
- struct snd_pcm_runtime *runtime = substream->runtime; area->vm_private_data = substream;
- area->vm_flags |= VM_RESERVED;
- dma_mmap_coherent(NULL, area, runtime->dma_area,
runtime->dma_addr, runtime->dma_bytes);} _______________________________________________ Alsa-devel mailing list Alsa-devel@alsa-project.org http://mailman.alsa-project.org/mailman/listinfo/alsa-devel