From: Will Deacon <will.deacon@arm.com>
To: Rob Herring <robherring2@gmail.com>
Cc: "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
Russell King <linux@arm.linux.org.uk>,
Arnd Bergmann <arnd@arndb.de>,
Linus Walleij <linus.walleij@linaro.org>,
Magnus Damm <magnus.damm@gmail.com>,
"grant.likely@linaro.org" <grant.likely@linaro.org>,
Rob Herring <robh+dt@kernel.org>,
Santosh Shilimkar <santosh.shilimkar@ti.com>,
Olof Johansson <olof@lixom.net>,
dave.martin@arm.com,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v2 4/7] dma: of: introduce of_dma_is_coherent() helper
Date: Tue, 4 Mar 2014 15:21:37 +0000 [thread overview]
Message-ID: <20140304152137.GL8766@mudshark.cambridge.arm.com> (raw)
In-Reply-To: <CAL_JsqLQrHwVx0ZbeeasKsTXp_NVMYX1voxhUdjH737tptiAeQ@mail.gmail.com>
On Mon, Mar 03, 2014 at 02:04:17PM +0000, Rob Herring wrote:
> Adding Will...
Thanks Rob!
> On Fri, Feb 28, 2014 at 9:24 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> > On Friday 28 February 2014 09:14:19 Rob Herring wrote:
> >>
> >> I know Will D was not a fan of this property. Primarily I believe
> >> because you may need to describe more than just a boolean in more
> >> complex bus topologies.
> >
> > I can't think of any example where it's not per-device. Do you
> > think we can end up with a device that has multiple bus master
> > ports, only some of which are coherent, or is there a different
> > concern?
>
> Perhaps Will can post his slides from the ARM kernel summit or chime
> in here, but I believe it was more that coherency is just one aspect
> of bus master bus topology. The DT models the slave bus hierarchy and
> doesn't model the master side which is becoming more complex and
> needing to be described. In the case of highbank, you have an ACP bus
> with some number of masters on it. They are configurable, but it is
> not the device that is configurable, but really which bus they are
> connected to.
I'm not sure what happened to this slides but, yes, you have the right idea.
It's not only DMA coherency that's directly related to master topology, but
also SMMU configuration and MSI routing will depend on this information.
Using a per-device, boolean property to describe DMA coherency may work for a
simple, statically configured system, but it really just avoids the bigger
issue.
Will
WARNING: multiple messages have this Message-ID (diff)
From: will.deacon@arm.com (Will Deacon)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2 4/7] dma: of: introduce of_dma_is_coherent() helper
Date: Tue, 4 Mar 2014 15:21:37 +0000 [thread overview]
Message-ID: <20140304152137.GL8766@mudshark.cambridge.arm.com> (raw)
In-Reply-To: <CAL_JsqLQrHwVx0ZbeeasKsTXp_NVMYX1voxhUdjH737tptiAeQ@mail.gmail.com>
On Mon, Mar 03, 2014 at 02:04:17PM +0000, Rob Herring wrote:
> Adding Will...
Thanks Rob!
> On Fri, Feb 28, 2014 at 9:24 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> > On Friday 28 February 2014 09:14:19 Rob Herring wrote:
> >>
> >> I know Will D was not a fan of this property. Primarily I believe
> >> because you may need to describe more than just a boolean in more
> >> complex bus topologies.
> >
> > I can't think of any example where it's not per-device. Do you
> > think we can end up with a device that has multiple bus master
> > ports, only some of which are coherent, or is there a different
> > concern?
>
> Perhaps Will can post his slides from the ARM kernel summit or chime
> in here, but I believe it was more that coherency is just one aspect
> of bus master bus topology. The DT models the slave bus hierarchy and
> doesn't model the master side which is becoming more complex and
> needing to be described. In the case of highbank, you have an ACP bus
> with some number of masters on it. They are configurable, but it is
> not the device that is configurable, but really which bus they are
> connected to.
I'm not sure what happened to this slides but, yes, you have the right idea.
It's not only DMA coherency that's directly related to master topology, but
also SMMU configuration and MSI routing will depend on this information.
Using a per-device, boolean property to describe DMA coherency may work for a
simple, statically configured system, but it really just avoids the bigger
issue.
Will
next prev parent reply other threads:[~2014-03-04 15:21 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-27 21:17 [PATCH v2 0/7] ARM: dma: Support dma-ranges and dma-coherent Santosh Shilimkar
2014-02-27 21:17 ` Santosh Shilimkar
2014-02-27 21:17 ` [PATCH v2 1/7] ARM: mm: Introduce archdata.dma_pfn_offset Santosh Shilimkar
2014-02-27 21:17 ` Santosh Shilimkar
[not found] ` <1393535872-20915-2-git-send-email-santosh.shilimkar-l0cyMroinI0@public.gmane.org>
2014-02-28 9:30 ` Arnd Bergmann
2014-02-28 9:30 ` Arnd Bergmann
2014-03-05 4:45 ` Linus Walleij
2014-03-05 4:45 ` Linus Walleij
[not found] ` <CACRpkdaRgf2yn51HYnJHBVKdrGdYhwSr0yf2GLmT3DwzmPbMDA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-03-05 6:37 ` Santosh Shilimkar
2014-03-05 6:37 ` Santosh Shilimkar
[not found] ` <1393535872-20915-1-git-send-email-santosh.shilimkar-l0cyMroinI0@public.gmane.org>
2014-02-27 21:17 ` [PATCH v2 2/7] ARM: mm: Remove unsed dma_to_virt() Santosh Shilimkar
2014-02-27 21:17 ` Santosh Shilimkar
[not found] ` <1393535872-20915-3-git-send-email-santosh.shilimkar-l0cyMroinI0@public.gmane.org>
2014-02-28 9:31 ` Arnd Bergmann
2014-02-28 9:31 ` Arnd Bergmann
2014-03-07 5:59 ` Greg Ungerer
2014-03-07 5:59 ` Greg Ungerer
2014-02-27 21:17 ` [PATCH v2 3/7] dma: of: introduce of_dma_get_range() helper Santosh Shilimkar
2014-02-27 21:17 ` Santosh Shilimkar
2014-02-27 21:17 ` [PATCH v2 4/7] dma: of: introduce of_dma_is_coherent() helper Santosh Shilimkar
2014-02-27 21:17 ` Santosh Shilimkar
2014-02-28 9:39 ` Arnd Bergmann
2014-02-28 9:39 ` Arnd Bergmann
2014-02-28 14:17 ` Santosh Shilimkar
2014-02-28 14:17 ` Santosh Shilimkar
[not found] ` <53109A64.9030701-l0cyMroinI0@public.gmane.org>
2014-03-03 1:49 ` Catalin Marinas
2014-03-03 1:49 ` Catalin Marinas
2014-02-28 15:14 ` Rob Herring
2014-02-28 15:14 ` Rob Herring
[not found] ` <CAL_JsqL6-hoD4F7+adPhsOJXeM5f+wpEuBWg_6AWqj3k2v0NEw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-02-28 15:17 ` Santosh Shilimkar
2014-02-28 15:17 ` Santosh Shilimkar
2014-02-28 15:24 ` Arnd Bergmann
2014-02-28 15:24 ` Arnd Bergmann
2014-03-03 14:04 ` Rob Herring
2014-03-03 14:04 ` Rob Herring
2014-03-04 15:21 ` Will Deacon [this message]
2014-03-04 15:21 ` Will Deacon
2014-02-27 21:17 ` [PATCH v2 5/7] ARM: of: introduce common routine for DMA configuration Santosh Shilimkar
2014-02-27 21:17 ` Santosh Shilimkar
2014-02-28 10:00 ` Arnd Bergmann
2014-02-28 10:00 ` Arnd Bergmann
2014-02-28 11:49 ` Grygorii Strashko
2014-02-28 11:49 ` Grygorii Strashko
2014-02-28 11:14 ` Arnd Bergmann
2014-02-28 11:14 ` Arnd Bergmann
2014-02-28 15:06 ` Santosh Shilimkar
2014-02-28 15:06 ` Santosh Shilimkar
[not found] ` <5310A5F1.9070901-l0cyMroinI0@public.gmane.org>
2014-02-28 15:31 ` Arnd Bergmann
2014-02-28 15:31 ` Arnd Bergmann
2014-02-28 15:35 ` Santosh Shilimkar
2014-02-28 15:35 ` Santosh Shilimkar
2014-03-07 3:15 ` Linus Walleij
2014-03-07 3:15 ` Linus Walleij
[not found] ` <1393535872-20915-6-git-send-email-santosh.shilimkar-l0cyMroinI0@public.gmane.org>
2014-02-28 14:56 ` Rob Herring
2014-02-28 14:56 ` Rob Herring
2014-02-27 21:17 ` [PATCH v2 6/7] ARM: dts: keystone: Use dma-ranges property Santosh Shilimkar
2014-02-27 21:17 ` Santosh Shilimkar
2014-02-27 21:17 ` [PATCH v2 7/7] ARM: dts: keystone: Udate USB node for dma properties Santosh Shilimkar
2014-02-27 21:17 ` Santosh Shilimkar
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20140304152137.GL8766@mudshark.cambridge.arm.com \
--to=will.deacon@arm.com \
--cc=arnd@arndb.de \
--cc=dave.martin@arm.com \
--cc=devicetree@vger.kernel.org \
--cc=grant.likely@linaro.org \
--cc=linus.walleij@linaro.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux@arm.linux.org.uk \
--cc=magnus.damm@gmail.com \
--cc=olof@lixom.net \
--cc=robh+dt@kernel.org \
--cc=robherring2@gmail.com \
--cc=santosh.shilimkar@ti.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.