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Re: [PATCH 3/5] ALSA: pcm - fix page conversion on non-coherent MIPS arc

To: Takashi Iwai <>
Subject: Re: [PATCH 3/5] ALSA: pcm - fix page conversion on non-coherent MIPS arch
From: Ralf Baechle <>
Date: Fri, 27 Nov 2009 08:46:35 +0000
Cc:, Wu Zhangjin <>, Thomas Bogendoerfer <>,, Benjamin Herrenschmidt <>, Kumar Gala <>, Becky Bruce <>
In-reply-to: <>
Original-recipient: rfc822;
References: <> <> <> <>
User-agent: Mutt/1.5.20 (2009-08-17)
On Thu, Nov 26, 2009 at 04:13:06PM +0100, Takashi Iwai wrote:

> The non-coherent MIPS arch doesn't give the correct address by a simple
> virt_to_page() for pages allocated via dma_alloc_coherent().
> Original patch by Wu Zhangjin <>.  A proper check of the
> buffer allocation type was added to avoid the wrong conversion.

The origins of this patch go back far further.  The oldest patch I could
find which is a superset of this was written by Atsushi Nemoto and
various incarnations of it have been sumitted to and reject by me
a number of times through the years.

> Note that this doesn't fix perfectly: the pages should be marked with
> proper pgprot value.  This will be done in a future implementation like
> the conversion to dma_mmap_coherent().
> Signed-off-by: Takashi Iwai <>

So while this is ugly I don't think this patch will actually make the
the situation worse for any MIPS platform.  So with both eyes closed:

Acked-by: Ralf Baechle <>


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