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Subject: Re: [PATCH] iommu/tegra-smmu: Fix mc errors on tegra124-nyan
To:     Nicolin Chen <nicoleotsuka@gmail.com>, joro@8bytes.org,
        thierry.reding@gmail.com, will@kernel.org,
        guillaume.tucker@collabora.com
Cc:     vdumpa@nvidia.com, jonathanh@nvidia.com,
        linux-tegra@vger.kernel.org, iommu@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org
References: <20210218220702.1962-1-nicoleotsuka@gmail.com>
From:   Dmitry Osipenko <digetx@gmail.com>
Message-ID: <9d6445c0-9574-1650-e327-32b11716f87e@gmail.com>
Date:   Sat, 20 Feb 2021 08:16:22 +0300
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19.02.2021 01:07, Nicolin Chen пишет:
> Commit 25938c73cd79 ("iommu/tegra-smmu: Rework tegra_smmu_probe_device()")
> removed certain hack in the tegra_smmu_probe() by relying on IOMMU core to
> of_xlate SMMU's SID per device, so as to get rid of tegra_smmu_find() and
> tegra_smmu_configure() that are typically done in the IOMMU core also.
> 
> This approach works for both existing devices that have DT nodes and other
> devices (like PCI device) that don't exist in DT, on Tegra210 and Tegra3
> upon testing. However, Page Fault errors are reported on tegra124-Nyan:
> 
>   tegra-mc 70019000.memory-controller: display0a: read @0xfe056b40:
> 	 EMEM address decode error (SMMU translation error [--S])
>   tegra-mc 70019000.memory-controller: display0a: read @0xfe056b40:
> 	 Page fault (SMMU translation error [--S])
> 
> After debugging, I found that the mentioned commit changed some function
> callback sequence of tegra-smmu's, resulting in enabling SMMU for display
> client before display driver gets initialized. I couldn't reproduce exact
> same issue on Tegra210 as Tegra124 (arm-32) differs at arch-level code.

Hello Nicolin,

Could you please explain in a more details what exactly makes the
difference for the callback sequence?