linux-kernel - Re: [PATCH 3/5] dt-bindings: mediatek: Add smi dts binding

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Date:	Tue, 14 Apr 2015 11:06:58 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	Yong Wu <yong.wu@...iatek.com>
Cc:	Rob Herring <robh+dt@...nel.org>, Joerg Roedel <joro@...tes.org>,
	Matthias Brugger <matthias.bgg@...il.com>,
	Robin Murphy <Robin.Murphy@....com>,
	Will Deacon <Will.Deacon@....com>,
	Daniel Kurtz <djkurtz@...gle.com>,
	Tomasz Figa <tfiga@...gle.com>,
	Lucas Stach <l.stach@...gutronix.de>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"linux-mediatek@...ts.infradead.org" 
	<linux-mediatek@...ts.infradead.org>,
	Sasha Hauer <kernel@...gutronix.de>,
	"srv_heupstream@...iatek.com" <srv_heupstream@...iatek.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>
Subject: Re: [PATCH 3/5] dt-bindings: mediatek: Add smi dts binding

On Tue, Apr 14, 2015 at 10:07:54AM +0100, Yong Wu wrote:
> Hi Mark,
>     Thanks very much for review. 
>     About the clock name should be the PoV of _this_ device. Could you
> help check below?
> 
> On Fri, 2015-03-06 at 11:13 +0000, Mark Rutland wrote:
> > On Fri, Mar 06, 2015 at 10:48:18AM +0000, yong.wu@...iatek.com wrote:
> > > From: Yong Wu <yong.wu@...iatek.com>
> > > 
> > > This patch add smi binding document.
> > 
> > Please move binding documents to the start of the series. It makes
> > things far easier to review.
> > 
> > > 
> > > Signed-off-by: Yong Wu <yong.wu@...iatek.com>
> > > +++ b/Documentation/devicetree/bindings/soc/mediatek/mediatek,smi.txt
> > > @@ -0,0 +1,17 @@
> > > +SMI hardware block diagram please help check <bindings/iommu/mediatek,iommu.txt>
> > > +
> > > +Required properties:
> > > +- compatible : must be "mediatek,mediatek,mt8173-smi-larb"
> > 
> > Double vendor prefix?
> > 
> > What does "larb" mean? It would be nice for the intorductory paragraph
> > in this file to explain.
> > 
> > > +- reg : the register of each local arbiter
> > > +- clocks : the clocks of each local arbiter
> > > +- clock-name: larb_sub*(3 clockes at most)
> > 
> > The names required _must_ be specified here, or clock-names is
> > pointless.
> > 
> > The clock names should be from the PoV of _this_ device (i.e. they
> > should be the names of the inputs) not from the PoV of the provider
> > (i.e. they should not be the names of the outputs from the provider).
> > 
> > Mark.
> > 
>      After we check with our SMI Designer. Every SMI local arbiter need
> two clocks, which is called  APB clocks and SMI clock.
>      APB clock : Advanced Peripheral Bus Clock. It is the clock for
> setting the register of local arbiter.
>      SMI clock : Smart Multimedia Interface Clock, It is the clock for
> transfering the data and command. 
> 
>      And all the local arbiters need the smi common clock, so we
> separate it. 
> 
>      Then I prepare to design the smi the dtsi like this: 
> 
>       smi_common:smi@...22000 {
>                  compatible = “mediate, mt8173-smi”;
>                  reg = <0 0x14022000 0 0x1000>;
>                  clocks = <&mmsys MM_SMI_COMMON>;
>                  clocks-names = “smi_common”;
>       };
> 
>       larb0: larb@...21000 {
>                  compatible = “mediate, mt8173-smi-larb”;
>                  reg = <0 0x14021000 0 0x1000>;
>                  smi = <&smi_common>;
>                  clocks = <&mmsys MM_SMI_LARB0>, 
> 		 	<&mmsys MM_SMI_LARB0>;
>                  clocks-names = “apb_clk”, “smi_clk”;
>      };
> 
>      larb1: larb@...10000 {
>                  compatible = “mediate, mt8173-smi-larb”;
>                  reg = <0 0x16010000 0 0x1000>;
>                  smi = <&smi_common>;
>                  clocks = <&vdecsys VDEC_CKEN>, 
> 			 <&mmsys VDEC_LARB_CKEN>;
>                  clocks-names = “apb_clk”, “smi_clk”;
>       };
>       … 
>      In some local arbiter, the source clock of the APB clock and the
> SMI clock may be the same, like larb0. so the two clocks are the same.
> And they may be different in other local arbiteres, like larb1.      
> 
>      If it is designed like this, is it ok?

That looks pretty good; the clocks and names on the larb nodes seem
sensible.

The naming of the "smi_common" clock on the smi_common node looks a bit
odd though. Is that really what the clock input is called?

Mark.
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