linux-mips
[Top] [All Lists]

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

To: Takashi Iwai <tiwai@suse.de>
Subject: Re: [PATCH 3/5] ALSA: pcm - fix page conversion on non-coherent MIPS arch
From: Ralf Baechle <ralf@linux-mips.org>
Date: Fri, 27 Nov 2009 08:46:35 +0000
Cc: alsa-devel@alsa-project.org, Wu Zhangjin <wuzhangjin@gmail.com>, Thomas Bogendoerfer <tsbogend@alpha.franken.de>, linux-mips@linux-mips.org, Benjamin Herrenschmidt <benh@kernel.crashing.org>, Kumar Gala <galak@gate.crashing.org>, Becky Bruce <beckyb@kernel.crashing.org>
In-reply-to: <1259248388-20095-4-git-send-email-tiwai@suse.de>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <1259248388-20095-1-git-send-email-tiwai@suse.de> <1259248388-20095-2-git-send-email-tiwai@suse.de> <1259248388-20095-3-git-send-email-tiwai@suse.de> <1259248388-20095-4-git-send-email-tiwai@suse.de>
Sender: linux-mips-bounce@linux-mips.org
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 <wuzj@lemote.com>.  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 <tiwai@suse.de>

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 <ralf@linux-mips.org>

  Ralf

<Prev in Thread] Current Thread [Next in Thread>