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References: <20210326231303.3071950-1-eric@anholt.net> <20210329144729.GB4203@willie-the-truck>
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From:   Rob Clark <robdclark@gmail.com>
Date:   Mon, 29 Mar 2021 21:02:50 -0700
Message-ID: <CAF6AEGugpEk396DVtWX=W+uf3p-wcgBfCSpSLWGQJE1vKpJ4aw@mail.gmail.com>
Subject: Re: [PATCH 1/2] iommu/arm-smmu-qcom: Skip the TTBR1 quirk for db820c.
To:     Will Deacon <will@kernel.org>
Cc:     Eric Anholt <eric@anholt.net>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        freedreno <freedreno@lists.freedesktop.org>,
        Sean Paul <sean@poorly.run>,
        Jordan Crouse <jcrouse@codeaurora.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Rob Herring <robh+dt@kernel.org>,
        Joerg Roedel <joro@8bytes.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@lists.infradead.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Mon, Mar 29, 2021 at 7:47 AM Will Deacon <will@kernel.org> wrote:
>
> On Fri, Mar 26, 2021 at 04:13:02PM -0700, Eric Anholt wrote:
> > db820c wants to use the qcom smmu path to get HUPCF set (which keeps
> > the GPU from wedging and then sometimes wedging the kernel after a
> > page fault), but it doesn't have separate pagetables support yet in
> > drm/msm so we can't go all the way to the TTBR1 path.
>
> What do you mean by "doesn't have separate pagetables support yet"? The
> compatible string doesn't feel like the right way to determine this.

the compatible string identifies what it is, not what the sw
limitations are, so in that regard it seems right to me..

BR,
-R