linux-kernel - Re: [PATCH v8 06/12] ARM: dts: Add description of System MMU of Exynos SoCs

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Message-id: <20131008133853.8b8277b70d69e05edd011945@samsung.com>
Date:	Tue, 08 Oct 2013 13:38:53 +0900
From:	Cho KyongHo <pullip.cho@...sung.com>
To:	Rob Herring <robherring2@...il.com>
Cc:	Linux ARM Kernel <linux-arm-kernel@...ts.infradead.org>,
	Linux IOMMU <iommu@...ts.linux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Linux Samsung SOC <linux-samsung-soc@...r.kernel.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Hyunwoong Kim <khw0178.kim@...sung.com>,
	Prathyush <prathyush.k@...sung.com>,
	Grant Grundler <grundler@...omium.org>,
	Joerg Roedel <joro@...tes.org>,
	Keyyoung Park <keyyoung.park@...sung.com>,
	Subash Patel <supash.ramaswamy@...aro.org>,
	Sachin Kamat <sachin.kamat@...aro.org>,
	Antonios Motakis <a.motakis@...tualopensystems.com>,
	kvmarm@...ts.cs.columbia.edu,
	Rahul Sharma <rahul.sharma@...sung.com>,
	Will Deacon <will.deacon@....com>
Subject: Re: [PATCH v8 06/12] ARM: dts: Add description of System MMU of Exynos
 SoCs

On Mon, 07 Oct 2013 08:44:54 -0500, Rob Herring wrote:
> On Fri, Jul 26, 2013 at 6:28 AM, Cho KyongHo <pullip.cho@...sung.com> wrote:
> > Signed-off-by: Cho KyongHo <pullip.cho@...sung.com>
> > ---
> >  .../bindings/iommu/samsung,exynos4210-sysmmu.txt   |  103 +++++++
> >  arch/arm/boot/dts/exynos4.dtsi                     |  122 ++++++++
> >  arch/arm/boot/dts/exynos4210.dtsi                  |   25 ++
> >  arch/arm/boot/dts/exynos4x12.dtsi                  |   76 +++++
> >  arch/arm/boot/dts/exynos5250.dtsi                  |  291 ++++++++++++++++++++
> >  5 files changed, 617 insertions(+), 0 deletions(-)
> >  create mode 100644 Documentation/devicetree/bindings/iommu/samsung,exynos4210-sysmmu.txt
> >
> > diff --git a/Documentation/devicetree/bindings/iommu/samsung,exynos4210-sysmmu.txt
> > b/Documentation/devicetree/bindings/iommu/samsung,exynos4210-sysmmu.txt
> > new file mode 100644
> > index 0000000..92f0a33
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/iommu/samsung,exynos4210-sysmmu.txt
> > @@ -0,0 +1,103 @@
> > +Samsung Exynos4210 IOMMU H/W, System MMU (System Memory Management Unit)
> > +
> > +Samsung's Exynos architecture contains System MMU that enables scattered
> > +physical memory chunks visible as a contiguous region to DMA-capable peripheral
> > +devices like MFC, FIMC, FIMD, GScaler, FIMC-IS and so forth.
> > +
> > +System MMU is a sort of IOMMU and support identical translation table format to
> > +ARMv7 translation tables with minimum set of page properties including access
> > +permissions, shareability and security protection. In addition, System MMU has
> > +another capabilities like L2 TLB or block-fetch buffers to minimize translation
> > +latency.
> > +
> > +A System MMU is dedicated to a single master peripheral device.  Thus, it is
> > +important to specify the correct System MMU in the device node of its master
> > +device. Whereas a System MMU is dedicated to a master device, the master device
> > +may have more than one System MMU.
> > +
> > +Required properties:
> > +- compatible: Should be "samsung,exynos4210-sysmmu"
> > +- reg: A tuple of base address and size of System MMU registers.
> > +- interrupt-parent: The phandle of the interrupt controller of System MMU
> > +- interrupts: A tuple of numbers that indicates the interrupt source.
> > +- clock-names: Should be "sysmmu" if the System MMU is needed to gate its clock.
> > +               Please refer to the following documents:
> > +              Documentation/devicetree/bindings/clock/clock-bindings.txt
> > +              Documentation/devicetree/bindings/clock/exynos4-clock.txt
> > +              Documentation/devicetree/bindings/clock/exynos5250-clock.txt
> > +              Optional "master" if the clock to the System MMU is gated by
> > +              another gate clock other than "sysmmu". The System MMU driver
> > +              sets "master" the parent of "sysmmu".
> > +              Exynos4 SoCs, there needs no "master" clocks.
> > +              Exynos5 SoCs, some System MMUs must have "master" clocks.
> > +- clocks: Required if the System MMU is needed to gate its clock.
> > +         Please refer to the documents listed above.
> > +- samsung,power-domain: Required if the System MMU is needed to gate its power.
> > +         Please refer to the following document:
> > +         Documentation/devicetree/bindings/arm/exynos/power_domain.txt
> > +
> > +Required properties for the master peripheral devices:
> > +- iommu: phandles to the System MMUs of the device
> 
> You have not addressed my comments from the last version. We do not
> need 2 (or more) different ways to describe the connection between
> masters and iommu's. Use mmu-masters property here to describe the
> connection.
> 

Sorry, I forgot to reply.
I just thought the meaning of your comment that it should be align with ARM System MMU.
I now understand and it should be changed to mmu-masters property
because it is now in the kernel.

Thank you.


> Rob
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