On Wed, 16 May 2007 16:28:49 +0200, Martin Michlmayr <tbm@xxxxxxxxxx> wrote: > > There are know problems with PCI soundcard on noncoherent MIPS > > platform (including cobalt) and some patches are floating around. For > > example: > > http://www.linux-mips.org/archives/linux-mips/2007-04/msg00072.html > > > > This is a long standing issue and I wonder why your soundcard _did_ > > work with debian sid. The kernel of sid contains fixes for this > > issue? > > I don't think it ever worked with 2.6, but it certainly worked with > 2.4. Is it much work to get 2.6 working again? This problem comes up > from time to time, so it seems it's hitting a number of users. Did the 2.4 kernel use ALSA or OSS? I think ALSA for kernel 2.4 had same problem. And this is a minimal patch for current git tree. But I'm not sure if this patch really fixes the reported segfault. There are two problem. 1. virt_to_page() can not be used for a buffer returned by dma_alloc_coherent(). 2. mmap() for a buffer returned by dma_alloc_coherent() should be uncached. This patch is actually ugly and would not be acceptable as is. So we need a plan to how to fix them _right_ way. diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index a96733a..2d3660c 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -3138,6 +3138,9 @@ 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(CONFIG_MIPS) && defined(CONFIG_DMA_NONCOHERENT) + vaddr = CAC_ADDR(vaddr); +#endif page = virt_to_page(vaddr); } get_page(page); @@ -3159,6 +3162,10 @@ 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) { +#if defined(CONFIG_MIPS) && defined(CONFIG_DMA_NONCOHERENT) + /* use uncached access for dma_area */ + area->vm_page_prot = pgprot_noncached(area->vm_page_prot); +#endif area->vm_ops = &snd_pcm_vm_ops_data; area->vm_private_data = substream; area->vm_flags |= VM_RESERVED; diff --git a/sound/core/sgbuf.c b/sound/core/sgbuf.c index cefd228..1dd1c9e 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(CONFIG_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(CONFIG_MIPS) && defined(CONFIG_DMA_NONCOHERENT) + dmab->area = vmap(sgbuf->page_table, sgbuf->pages, VM_MAP, + PAGE_KERNEL_UNCACHED); +#else dmab->area = vmap(sgbuf->page_table, sgbuf->pages, VM_MAP, PAGE_KERNEL); +#endif if (! dmab->area) goto _failed; return dmab->area;
