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@xxxxxxxxxx> wrote:
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?
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
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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...:)
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);
atomic_inc(&substream->mmap_count);
return 0;
}
