linux-kernel - Re: [PATCH v3 6/6] iommu: mtk_iommu: Lookup phandle to retrieve syscon to pericfg

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Message-ID: <2d0f49294a8bac34dd5dd1ce4201f009a207b7a7.camel@mediatek.com>
Date:   Thu, 16 Jun 2022 14:30:57 +0800
From:   Yong Wu <yong.wu@...iatek.com>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
CC:     <joro@...tes.org>, <will@...nel.org>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <matthias.bgg@...il.com>,
        <iommu@...ts.linux-foundation.org>,
        <linux-mediatek@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <krzysztof.kozlowski@...aro.org>
Subject: Re: [PATCH v3 6/6] iommu: mtk_iommu: Lookup phandle to retrieve
 syscon to pericfg

On Mon, 2022-06-13 at 10:13 +0200, AngeloGioacchino Del Regno wrote:
> Il 13/06/22 07:32, Yong Wu ha scritto:
> > On Thu, 2022-06-09 at 12:08 +0200, AngeloGioacchino Del Regno
> > wrote:
> > > On some SoCs (of which only MT8195 is supported at the time of
> > > writing),
> > > the "R" and "W" (I/O) enable bits for the IOMMUs are in the
> > > pericfg_ao
> > > register space and not in the IOMMU space: as it happened already
> > > with
> > > infracfg, it is expected that this list will grow.
> > 
> > Currently I don't see the list will grow. As commented before, In
> > the
> > lastest SoC, The IOMMU enable bits for IOMMU will be in ATF, rather
> > than in this pericfg register region. In this case, Is this patch
> > unnecessary? or we could add this patch when there are 2 SoCs use
> > this
> > setting at least?  what's your opinion?
> > 
> 
> Perhaps I've misunderstood... besides, can you please check if
> there's any
> other SoC (not just chromebooks, also smartphone SoCs) that need this
> logic?

As far as I know, SmartPhone SoCs don't enable the infra iommu until
now. they don't have this logic. I don't object this patch, I think we
could add it when at least 2 SoCs need this.

Thanks very much for help improving here.

> 
> Thanks,
> Angelo
> 
>