From: David Brownell <david-b@pacbell.net>
To: Josh Boyer <jwboyer@gmail.com>
Cc: linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org,
Michael Trimarchi <trimarchimichael@yahoo.it>,
spi-devel-general@lists.sourceforge.net,
Andrew Morton <akpm@linux-foundation.org>,
dwmw2@infradead.org, linux-arm-kernel@lists.arm.linux.org.uk
Subject: Re: [PATCH] jffs2 summary allocation
Date: Fri, 4 Apr 2008 16:58:38 -0700 [thread overview]
Message-ID: <200804041658.38499.david-b@pacbell.net> (raw)
In-Reply-To: <1207351282.3224.79.camel@vader.jdub.homelinux.org>
On Friday 04 April 2008, Josh Boyer wrote:
>
> > ... This means specifically that you may _not_ use the
> > memory/addresses returned from vmalloc() for DMA. ...
> >
> > So I'm rather surprised to see *ANY* kernel code trying to do
> > that. That rule has been in effect for many, many years now.
>
> I don't think it was intentional. You're going through several layers
> here:
>
> JFFS2 -> mtd parts -> mtd dataflash -> atmel_spi.
>
> Typically MTD drivers aren't doing DMAs to flash and JFFS2 has no idea
> which particular chip driver is being used because it's abstracted by
> MTD.
That's true ... although I can imagine using DMA to
avoid dcache trashing if its setup cost is low enough,
with either NAND or NOR chips.
Still: in this context vmalloc() is wrong.
- Dave
WARNING: multiple messages have this Message-ID (diff)
From: David Brownell <david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org>
To: Josh Boyer <jwboyer-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-mtd-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
Michael Trimarchi <trimarchimichael-whZMOeQn8C0@public.gmane.org>,
spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org,
Andrew Morton
<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
dwmw2-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org,
linux-arm-kernel-xIg/pKzrS19vn6HldHNs0ANdhmdF6hFW@public.gmane.org
Subject: Re: [PATCH] jffs2 summary allocation
Date: Fri, 4 Apr 2008 16:58:38 -0700 [thread overview]
Message-ID: <200804041658.38499.david-b@pacbell.net> (raw)
In-Reply-To: <1207351282.3224.79.camel-ao9So7SQ8LBXjJKHA5322XviChZXdy27@public.gmane.org>
On Friday 04 April 2008, Josh Boyer wrote:
>
> > ... This means specifically that you may _not_ use the
> > memory/addresses returned from vmalloc() for DMA. ...
> >
> > So I'm rather surprised to see *ANY* kernel code trying to do
> > that. That rule has been in effect for many, many years now.
>
> I don't think it was intentional. You're going through several layers
> here:
>
> JFFS2 -> mtd parts -> mtd dataflash -> atmel_spi.
>
> Typically MTD drivers aren't doing DMAs to flash and JFFS2 has no idea
> which particular chip driver is being used because it's abstracted by
> MTD.
That's true ... although I can imagine using DMA to
avoid dcache trashing if its setup cost is low enough,
with either NAND or NOR chips.
Still: in this context vmalloc() is wrong.
- Dave
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WARNING: multiple messages have this Message-ID (diff)
From: David Brownell <david-b@pacbell.net>
To: Josh Boyer <jwboyer@gmail.com>
Cc: linux-arm-kernel@lists.arm.linux.org.uk,
Andrew Morton <akpm@linux-foundation.org>,
Michael Trimarchi <trimarchimichael@yahoo.it>,
dwmw2@infradead.org, spi-devel-general@lists.sourceforge.net,
linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] jffs2 summary allocation
Date: Fri, 4 Apr 2008 16:58:38 -0700 [thread overview]
Message-ID: <200804041658.38499.david-b@pacbell.net> (raw)
In-Reply-To: <1207351282.3224.79.camel@vader.jdub.homelinux.org>
On Friday 04 April 2008, Josh Boyer wrote:
>
> > ... This means specifically that you may _not_ use the
> > memory/addresses returned from vmalloc() for DMA. ...
> >
> > So I'm rather surprised to see *ANY* kernel code trying to do
> > that. That rule has been in effect for many, many years now.
>
> I don't think it was intentional. You're going through several layers
> here:
>
> JFFS2 -> mtd parts -> mtd dataflash -> atmel_spi.
>
> Typically MTD drivers aren't doing DMAs to flash and JFFS2 has no idea
> which particular chip driver is being used because it's abstracted by
> MTD.
That's true ... although I can imagine using DMA to
avoid dcache trashing if its setup cost is low enough,
with either NAND or NOR chips.
Still: in this context vmalloc() is wrong.
- Dave
next prev parent reply other threads:[~2008-04-04 23:58 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-04-04 10:23 [PATCH] jffs2 summary allocation Michael Trimarchi
2008-04-04 10:23 ` Michael Trimarchi
2008-04-04 19:48 ` Andrew Morton
2008-04-04 19:48 ` Andrew Morton
2008-04-04 19:48 ` Andrew Morton
2008-04-04 20:09 ` Russell King - ARM Linux
2008-04-04 20:09 ` Russell King - ARM Linux
2008-04-04 20:09 ` Russell King - ARM Linux
2008-04-04 23:09 ` David Brownell
2008-04-04 23:09 ` David Brownell
2008-04-04 23:09 ` David Brownell
2008-04-04 23:21 ` Josh Boyer
2008-04-04 23:21 ` Josh Boyer
2008-04-04 23:21 ` Josh Boyer
2008-04-04 23:58 ` David Brownell [this message]
2008-04-04 23:58 ` David Brownell
2008-04-04 23:58 ` David Brownell
2008-04-05 1:11 ` Josh Boyer
2008-04-05 1:11 ` Josh Boyer
2008-04-05 1:11 ` Josh Boyer
2008-04-05 1:29 ` Kyungmin Park
2008-04-05 1:29 ` Kyungmin Park
2008-04-05 1:29 ` Kyungmin Park
2008-04-05 1:46 ` Andrew Morton
2008-04-05 1:46 ` Andrew Morton
2008-04-05 1:46 ` Andrew Morton
2008-04-05 2:41 ` David Brownell
2008-04-05 2:41 ` David Brownell
2008-04-05 2:41 ` David Brownell
2008-04-05 3:27 ` Andrew Morton
2008-04-05 3:27 ` Andrew Morton
2008-04-05 3:27 ` Andrew Morton
2008-04-05 2:17 ` David Brownell
2008-04-05 2:17 ` David Brownell
2008-04-05 2:17 ` David Brownell
-- strict thread matches above, loose matches on Subject: below --
2008-04-05 14:05 matthieu castet
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