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Re: ALSA on MIPS platform

To: "Songmao Tian" <tiansm@lemote.com>
Subject: Re: ALSA on MIPS platform
From: "Dajie Tan" <jiankemeng@gmail.com>
Date: Tue, 7 Aug 2007 09:53:15 +0400
Cc: linux-mips@linux-mips.org, alsa-devel@alsa-project.org, Ralf <ralf@linux-mips.org>, "Atsushi Nemoto" <anemo@mba.ocn.ne.jp>, "Takashi Iwai" <tiwai@suse.de>, greg@kroah.com
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I think this problem can be solved by revising the __pa macro like this:

--- a/include/asm-mips/page.h      2007-08-07 09:45:00.000000000 +0800
+++ b/include/asm-mips/page.h     2007-08-07 09:46:59.000000000 +0800
@@ -150,7 +150,7 @@
 })
 #else
 #define __pa(x)
         \
-    ((unsigned long)(x) - PAGE_OFFSET + PHYS_OFFSET)
+    (((unsigned long)(x) & 0x1fffffff) + PHYS_OFFSET)
 #endif

So, the virt_to_page can accept all cached or uncached address.


Tan

2007/8/3, Songmao Tian <tiansm@lemote.com>:
> Atsushi Nemoto wrote:
> > On Wed, 01 Aug 2007 15:56:48 +0800, Songmao Tian <tiansm@lemote.com> 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:(
>
>
> dma_virt_to_page can be something like this.
>
> diff --git a/include/asm-mips/page.h b/include/asm-mips/page.h
> index b92dd8c..d2ead8a 100644
> --- a/include/asm-mips/page.h
> +++ b/include/asm-mips/page.h
> @@ -181,6 +181,8 @@ typedef struct { unsigned long pgprot; } pgprot_t;
>  #define virt_to_page(kaddr)    pfn_to_page(PFN_DOWN(virt_to_phys(kaddr)))
>  #define virt_addr_valid(kaddr)    pfn_valid(PFN_DOWN(virt_to_phys(kaddr)))
>
> +#define dma_virt_to_page(dma_addr)
> pfn_to_page(PFN_DOWN(virt_to_phys(CAC_ADDR(kaddr))))
> +
>  #define VM_DATA_DEFAULT_FLAGS    (VM_READ | VM_WRITE | VM_EXEC | \
>                   VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 655094d..5e694dd 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -39,6 +39,10 @@ extern int sysctl_legacy_va_layout;
>  #include <asm/pgtable.h>
>  #include <asm/processor.h>
>
> +#ifndef dma_virt_to_page
> +#define dma_virt_to_page virt_to_page
> +#endif
> +
>  #define nth_page(page,n) pfn_to_page(page_to_pfn((page)) + (n))
>
>  /*
> diff --git a/sound/core/sgbuf.c b/sound/core/sgbuf.c
> index cefd228..8b29bfd 100644
> --- a/sound/core/sgbuf.c
> +++ b/sound/core/sgbuf.c
> @@ -91,7 +91,7 @@ void *snd_malloc_sgbuf_pages(struct device *device,
>          }
>          sgbuf->table[i].buf = tmpb.area;
>          sgbuf->table[i].addr = tmpb.addr;
> -        sgbuf->page_table[i] = virt_to_page(tmpb.area);
> +        sgbuf->page_table[i] = dma_virt_to_page(tmpb.area);
>          sgbuf->pages++;
>      }
>
>

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