linux-kernel - RE: [PATCH] RM64: dts: ls208xa: Add iommu-map property for pci

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Message-ID: <AM5PR0401MB2545B7C55F634D7B9CABAE629A9D0@AM5PR0401MB2545.eurprd04.prod.outlook.com>
Date:   Thu, 31 Aug 2017 10:41:38 +0000
From:   Bharat Bhushan <bharat.bhushan@....com>
To:     Marc Zyngier <marc.zyngier@....com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "ark.rutland@....com" <ark.rutland@....com>,
        "will.deacon@....com" <will.deacon@....com>,
        "oss@...error.net" <oss@...error.net>, Gang Liu <gang.liu@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "catalin.marinas@....com" <catalin.marinas@....com>
Subject: RE: [PATCH] RM64: dts: ls208xa: Add iommu-map property for pci


> -----Original Message-----
> From: Marc Zyngier [mailto:marc.zyngier@....com]
> Sent: Thursday, August 31, 2017 3:02 PM
> To: Bharat Bhushan <bharat.bhushan@....com>; robh+dt@...nel.org;
> ark.rutland@....com; will.deacon@....com; oss@...error.net; Gang Liu
> <gang.liu@....com>; devicetree@...r.kernel.org; linux-arm-
> kernel@...ts.infradead.org; linux-kernel@...r.kernel.org;
> catalin.marinas@....com
> Subject: Re: [PATCH] RM64: dts: ls208xa: Add iommu-map property for pci
> 
> On 31/08/17 10:23, Bharat Bhushan wrote:
> > This patch adds iommu-map property for PCIe, which enables SMMU for
> > these devices on LS208xA devices.
> >
> > Signed-off-by: Bharat Bhushan <Bharat.Bhushan@....com>
> > ---
> >  arch/arm64/boot/dts/freescale/fsl-ls208xa.dtsi | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/arch/arm64/boot/dts/freescale/fsl-ls208xa.dtsi
> > b/arch/arm64/boot/dts/freescale/fsl-ls208xa.dtsi
> > index 94cdd30..67cf605 100644
> > --- a/arch/arm64/boot/dts/freescale/fsl-ls208xa.dtsi
> > +++ b/arch/arm64/boot/dts/freescale/fsl-ls208xa.dtsi
> > @@ -606,6 +606,7 @@
> >  			num-lanes = <4>;
> >  			bus-range = <0x0 0xff>;
> >  			msi-parent = <&its>;
> > +			iommu-map = <0 &smmu 0 1>;	/* This is fixed-up by
> u-boot */
> 
> What does this do when your version of u-boot doesn't fill this in for you?

Good question, frankly I have not thought of this case before.
But if we pass length = 0 in above property then no fixup happen with happen with older u-boot. In this case of_iommu_configure() will return NULL iommu-ops and it switch to swio-tlb. Will that work?

Thanks
-Bharat

> 
> Thanks,
> 
> 	M.
> --
> Jazz is not dead. It just smells funny...