From: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>
To: linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
Cc: Rob Herring <robherring2-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
"devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Russell King <linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>,
Linus Walleij
<linus.walleij-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>,
Magnus Damm <magnus.damm-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
Olof Johansson <olof-nZhT3qVonbNeoWH0uzbU5w@public.gmane.org>,
Rob Herring <robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Santosh Shilimkar
<santosh.shilimkar-l0cyMroinI0@public.gmane.org>,
Grant Likely
<grant.likely-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
Subject: Re: [PATCH v2 4/7] dma: of: introduce of_dma_is_coherent() helper
Date: Fri, 28 Feb 2014 16:24:56 +0100 [thread overview]
Message-ID: <5773663.p5fEFmy536@wuerfel> (raw)
In-Reply-To: <CAL_JsqL6-hoD4F7+adPhsOJXeM5f+wpEuBWg_6AWqj3k2v0NEw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
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?
> Effectively, highbank is always coherent. It was only PCI that is
> non-coherent, but I can safely say PCI will never be enabled at this
> point. There are no designs with PCI beyond 1 or 2 validation boards
> (total boards, not designs), and getting PCI to work was quite hacky
> due to only a 1MB window. The other masters are programmable, but only
> the coherent path is used as the non-coherent path actually has some
> issues. I had expected the opposite believing the ACP port would
> actually have issues which is also why I made it configurable.
Ok, I see. I still expect that we will see systems that are only
partially coherent in the future, but it's good to know we don't really
have to deal with backwards-compatibility as long as we can just
hardcode highbank to be always coherent.
I'm especially thankful we don't have to deal with the PCI implementation.
Arnd
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WARNING: multiple messages have this Message-ID (diff)
From: arnd@arndb.de (Arnd Bergmann)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2 4/7] dma: of: introduce of_dma_is_coherent() helper
Date: Fri, 28 Feb 2014 16:24:56 +0100 [thread overview]
Message-ID: <5773663.p5fEFmy536@wuerfel> (raw)
In-Reply-To: <CAL_JsqL6-hoD4F7+adPhsOJXeM5f+wpEuBWg_6AWqj3k2v0NEw@mail.gmail.com>
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?
> Effectively, highbank is always coherent. It was only PCI that is
> non-coherent, but I can safely say PCI will never be enabled at this
> point. There are no designs with PCI beyond 1 or 2 validation boards
> (total boards, not designs), and getting PCI to work was quite hacky
> due to only a 1MB window. The other masters are programmable, but only
> the coherent path is used as the non-coherent path actually has some
> issues. I had expected the opposite believing the ACP port would
> actually have issues which is also why I made it configurable.
Ok, I see. I still expect that we will see systems that are only
partially coherent in the future, but it's good to know we don't really
have to deal with backwards-compatibility as long as we can just
hardcode highbank to be always coherent.
I'm especially thankful we don't have to deal with the PCI implementation.
Arnd
next prev parent reply other threads:[~2014-02-28 15:24 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 [this message]
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
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
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