linux-kernel - Re: [PATCH] iommu/arm-smmu-qcom: Add missing GMU entry to match table

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Message-ID: <ZXLRjDZn9bgiREPf@hovoldconsulting.com>
Date:   Fri, 8 Dec 2023 09:19:24 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Rob Clark <robdclark@...il.com>
Cc:     iommu@...ts.linux-foundation.org, freedreno@...ts.freedesktop.org,
        linux-arm-msm@...r.kernel.org, Rob Clark <robdclark@...omium.org>,
        Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Bjorn Andersson <quic_bjorande@...cinc.com>,
        Elliot Berman <quic_eberman@...cinc.com>,
        Richard Acayan <mailingradian@...il.com>,
        Manivannan Sadhasivam <mani@...nel.org>,
        "moderated list:ARM SMMU DRIVERS" 
        <linux-arm-kernel@...ts.infradead.org>,
        "open list:IOMMU SUBSYSTEM" <iommu@...ts.linux.dev>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] iommu/arm-smmu-qcom: Add missing GMU entry to match table

On Thu, Dec 07, 2023 at 01:24:39PM -0800, Rob Clark wrote:
> From: Rob Clark <robdclark@...omium.org>
> 
> We also want the default domain for the GMU to be an identy domain,
> so it does not get a context bank assigned.  Without this, both
> of_dma_configure() and drm/msm's iommu_domain_attach() will trigger
> allocating and configuring a context bank.  So GMU ends up attached
> to both cbndx 1 and cbndx 2.  This arrangement seemingly confounds
> and surprises the firmware if the GPU later triggers a translation
> fault, resulting (on sc8280xp / lenovo x13s, at least) in the SMMU
> getting wedged and the GPU stuck without memory access.

This sounds like something that should be backported. Should you add a
Fixes and CC-stable tag?
 
> Signed-off-by: Rob Clark <robdclark@...omium.org>

Johan