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Date:   Mon, 11 Dec 2023 11:11:29 +0100
From:   Johan Hovold <johan@kernel.org>
To:     Rob Clark <robdclark@gmail.com>
Cc:     iommu@lists.linux-foundation.org, freedreno@lists.freedesktop.org,
        linux-arm-msm@vger.kernel.org, Robin Murphy <robin.murphy@arm.com>,
        Rob Clark <robdclark@chromium.org>, stable@vger.kernel.org,
        Will Deacon <will@kernel.org>, Joerg Roedel <joro@8bytes.org>,
        Konrad Dybcio <konrad.dybcio@linaro.org>,
        Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
        Bjorn Andersson <quic_bjorande@quicinc.com>,
        Manivannan Sadhasivam <mani@kernel.org>,
        Danila Tikhonov <danila@jiaxyga.com>,
        Elliot Berman <quic_eberman@quicinc.com>,
        "moderated list:ARM SMMU DRIVERS" 
        <linux-arm-kernel@lists.infradead.org>,
        "open list:IOMMU SUBSYSTEM" <iommu@lists.linux.dev>,
        open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] iommu/arm-smmu-qcom: Add missing GMU entry to match
 table
Message-ID: <ZXbgUeuf0-dYBOYV@hovoldconsulting.com>
References: <20231210180655.75542-1-robdclark@gmail.com>
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On Sun, Dec 10, 2023 at 10:06:53AM -0800, Rob Clark wrote:
> From: Rob Clark <robdclark@chromium.org>
> 
> In some cases the firmware expects cbndx 1 to be assigned to the GMU,
> so we also want the default domain for the GMU to be an identy domain.
> This way 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 later 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.
> 
> Cc: stable@vger.kernel.org
> Signed-off-by: Rob Clark <robdclark@chromium.org>

Tested-by: Johan Hovold <johan+linaro@kernel.org>