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Date:   Thu, 15 Jul 2021 10:46:44 +0200
From:   Oliver Graute <oliver.graute@kococonnector.com>
To:     Robin Murphy <robin.murphy@arm.com>
Cc:     shawnguo@kernel.org, devicetree@vger.kernel.org,
        aisheng.dong@nxp.com, fabio.estevam@nxp.com,
        Rob Herring <robh+dt@kernel.org>,
        Sascha Hauer <kernel@pengutronix.de>,
        Sascha Hauer <s.hauer@pengutronix.de>,
        Fabio Estevam <festevam@gmail.com>,
        NXP Linux Team <linux-imx@nxp.com>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1] arm64: dts: imx8qm: added System MMU
Message-ID: <20210715084644.GA28307@optiplex>
References: <20210714120925.23571-1-oliver.graute@kococonnector.com>
 <20210714120925.23571-3-oliver.graute@kococonnector.com>
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On 14/07/21, Robin Murphy wrote:
> On 2021-07-14 13:09, Oliver Graute wrote:
> > added node for System MMU
>=20
> Note that it's a bit of a dangerous game to enable an SMMU without the
> complete Stream ID topology for *all* its upstream devices also described=
,
> since CONFIG_ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT will ruin peoples' day. I=
t
> might be more polite to add it in a disabled state until every "iommus"
> property has been filled in, so that people who do want to play with it f=
or
> specific devices in the meantime can easily just flip the status (while
> taking the necessary precautions), but people who don't care won't be
> inadvertently affected regardless of their kernel config. I'm assuming an
> SMMU with 32 contexts has more than a single USB controller behind it...

thx for the explanation. So I will set this node to disabled state in
next version of this patch.
>=20
> >   	};
> > +	smmu: iommu@51400000 {
> > +		compatible =3D "arm,mmu-500";
> > +		interrupt-parent =3D <&gic>;
> > +		reg =3D <0 0x51400000 0 0x40000>;
> > +		#global-interrupts =3D <1>;
> > +		#iommu-cells =3D <2>;
> > +		interrupts =3D <0 32 4>,
> > +			     <0 32 4>, <0 32 4>, <0 32 4>, <0 32 4>,
> > +			     <0 32 4>, <0 32 4>, <0 32 4>, <0 32 4>,
> > +			     <0 32 4>, <0 32 4>, <0 32 4>, <0 32 4>,
> > +			     <0 32 4>, <0 32 4>, <0 32 4>, <0 32 4>,
> > +			     <0 32 4>, <0 32 4>, <0 32 4>, <0 32 4>,
> > +			     <0 32 4>, <0 32 4>, <0 32 4>, <0 32 4>,
> > +			     <0 32 4>, <0 32 4>, <0 32 4>, <0 32 4>,
> > +			     <0 32 4>, <0 32 4>, <0 32 4>, <0 32 4>;
		status =3D "disabled";
> > +	};

Best regards,

Oliver