From: thomas.petazzoni@free-electrons.com (Thomas Petazzoni)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH V4 5/5] arm: mvebu: Added SMP support for Armada XP
Date: Tue, 20 Nov 2012 18:07:59 +0100 [thread overview]
Message-ID: <20121120180759.27df512f@skate> (raw)
In-Reply-To: <20121120170127.GE27765@mudshark.cambridge.arm.com>
Dear Will Deacon,
On Tue, 20 Nov 2012 17:01:27 +0000, Will Deacon wrote:
> > I prefer to keep them separate, as we can use coherency without SMP.
> > That's why I create the coherency_ll.S file instead of putting
> > everything in this file.
>
> Hmm, can you elaborate a bit more on coherency without SMP please? Do
> these controls also affect IO coherency?
The coherency unit does coherency between CPUs, but also between the
CPU and the devices for DMA. So for example the MV78230 is a single-core
variant of the Armada XP, so having CONFIG_SMP for it is useless, but
you still want the CPU to join the coherency fabric in order to provide
coherency with I/O.
Thanks to the coherency unit, we have an almost DMA coherent
architecture (see the HW I/O coherency patches from Gr?gory for
details).
Thomas
--
Thomas Petazzoni, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com
WARNING: multiple messages have this Message-ID (diff)
From: Thomas Petazzoni <thomas.petazzoni-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
To: Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>
Cc: Lior Amsalem <alior-eYqpPyKDWXRBDgjK7y7TUQ@public.gmane.org>,
Andrew Lunn <andrew-g2DYL2Zd6BY@public.gmane.org>,
Ike Pan <ike.pan-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>,
Nadav Haklai <nadavh-eYqpPyKDWXRBDgjK7y7TUQ@public.gmane.org>,
Ian Molton <ian.molton-4yDnlxn2s6sWdaTGBSpHTA@public.gmane.org>,
David Marlin <dmarlin-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Yehuda Yitschak <yehuday-eYqpPyKDWXRBDgjK7y7TUQ@public.gmane.org>,
Jani Monoses
<jani.monoses-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>,
Russell King <linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>,
Tawfik Bayouk <tawfik-eYqpPyKDWXRBDgjK7y7TUQ@public.gmane.org>,
Dan Frazier
<dann.frazier-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>,
Eran Ben-Avi <benavi-eYqpPyKDWXRBDgjK7y7TUQ@public.gmane.org>,
Leif Lindholm <Leif.Lindholm-5wv7dgnIgG8@public.gmane.org>,
Sebastian Hesselbarth
<sebastian.hesselbarth-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
Jason Cooper <jason-NLaQJdtUoK4Be96aLqz0jA@public.gmane.org>,
"jcm-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org"
<jcm-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
"devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org"
<devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org>,
"rob.herring-bsGFqQB8/DxBDgjK7y7TUQ@public.gmane.org"
<rob.herring-bsGFqQB8/DxBDgjK7y7TUQ@public.gmane.org>,
Ben Dooks <ben-linux-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org>,
Mike Turquette
<mturquette-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>,
"linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org"
<linux-arm-kernel-IAPFreCvJWOunwaRDDq4rA@public.gmane.org>
Subject: Re: [PATCH V4 5/5] arm: mvebu: Added SMP support for Armada XP
Date: Tue, 20 Nov 2012 18:07:59 +0100 [thread overview]
Message-ID: <20121120180759.27df512f@skate> (raw)
In-Reply-To: <20121120170127.GE27765-MRww78TxoiP5vMa5CHWGZ34zcgK1vI+I0E9HWUfgJXw@public.gmane.org>
Dear Will Deacon,
On Tue, 20 Nov 2012 17:01:27 +0000, Will Deacon wrote:
> > I prefer to keep them separate, as we can use coherency without SMP.
> > That's why I create the coherency_ll.S file instead of putting
> > everything in this file.
>
> Hmm, can you elaborate a bit more on coherency without SMP please? Do
> these controls also affect IO coherency?
The coherency unit does coherency between CPUs, but also between the
CPU and the devices for DMA. So for example the MV78230 is a single-core
variant of the Armada XP, so having CONFIG_SMP for it is useless, but
you still want the CPU to join the coherency fabric in order to provide
coherency with I/O.
Thanks to the coherency unit, we have an almost DMA coherent
architecture (see the HW I/O coherency patches from Grégory for
details).
Thomas
--
Thomas Petazzoni, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com
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next prev parent reply other threads:[~2012-11-20 17:07 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-19 20:35 [PATCH V4 0/5] SMP support for Armada XP Gregory CLEMENT
2012-11-19 20:35 ` Gregory CLEMENT
2012-11-19 20:35 ` [PATCH V4 1/5] arm: mvebu: Added support for coherency fabric in mach-mvebu Gregory CLEMENT
2012-11-19 20:35 ` Gregory CLEMENT
2012-11-20 16:32 ` Will Deacon
2012-11-20 16:32 ` Will Deacon
2012-11-20 16:44 ` Gregory CLEMENT
2012-11-20 16:44 ` Gregory CLEMENT
2012-11-19 20:35 ` [PATCH V4 2/5] arm: mvebu: Added initial support for power managmement service unit Gregory CLEMENT
2012-11-19 20:35 ` Gregory CLEMENT
2012-11-19 20:35 ` [PATCH V4 3/5] arm: mvebu: Added IPI support via doorbells Gregory CLEMENT
2012-11-19 20:35 ` Gregory CLEMENT
2012-11-19 20:35 ` [PATCH V4 4/5] arm: mm: Added support for PJ4B cpu and init routines Gregory CLEMENT
2012-11-19 20:35 ` Gregory CLEMENT
2012-11-19 20:35 ` [PATCH V4 5/5] arm: mvebu: Added SMP support for Armada XP Gregory CLEMENT
2012-11-19 20:35 ` Gregory CLEMENT
2012-11-20 16:40 ` Will Deacon
2012-11-20 16:40 ` Will Deacon
2012-11-20 16:49 ` Gregory CLEMENT
2012-11-20 16:49 ` Gregory CLEMENT
2012-11-20 17:01 ` Will Deacon
2012-11-20 17:01 ` Will Deacon
2012-11-20 17:06 ` Gregory CLEMENT
2012-11-20 17:06 ` Gregory CLEMENT
2012-11-20 17:07 ` Thomas Petazzoni [this message]
2012-11-20 17:07 ` Thomas Petazzoni
2012-11-20 17:09 ` Will Deacon
2012-11-20 17:09 ` Will Deacon
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