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Subject: Re: [PATCH] iommu/tegra-smmu: Fix mc errors on tegra124-nyan
To:     Nicolin Chen <nicoleotsuka@gmail.com>
Cc:     joro@8bytes.org, thierry.reding@gmail.com, will@kernel.org,
        guillaume.tucker@collabora.com, 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>
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 <20210223021343.GA6539@Asurada-Nvidia>
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 <20210225062742.GA13353@Asurada-Nvidia>
 <ee0f40f4-dffe-2987-5d4b-c5896f27ec24@gmail.com>
 <20210302230856.GA22992@Asurada-Nvidia>
From:   Dmitry Osipenko <digetx@gmail.com>
Message-ID: <4a407ad8-33cb-94e9-398a-78fa65178e08@gmail.com>
Date:   Wed, 3 Mar 2021 12:47:28 +0300
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03.03.2021 02:08, Nicolin Chen пишет:
> On Sat, Feb 27, 2021 at 12:59:17PM +0300, Dmitry Osipenko wrote:
>> 25.02.2021 09:27, Nicolin Chen пишет:
>> ...
>>>> The partially revert should be okay, but it's not clear to me what makes
>>>> difference for T124 since I don't see that problem on T30, which also
>>>> has active display at a boot time.
>>>
>>> Hmm..do you see ->attach_dev() is called from host1x_client_iommu_attach
>>> or from of_dma_configure_id/arch_setup_dma_ops?
>>>
>>
>> I applied yours debug-patch, please see dmesg.txt attached to the email.
>> Seems probe-defer of the tegra-dc driver prevents the implicit
>> tegra_smmu_attach_dev, so it happens to work by accident.
> 
>> [    0.327826] tegra-dc 54200000.dc: -------tegra_smmu_of_xlate: id 1
>> [    0.328641] [<c052ec75>] (tegra_smmu_of_xlate) from [<c052e591>] (of_iommu_xlate+0x51/0x70)
>> [    0.328740] [<c052e591>] (of_iommu_xlate) from [<c052e6d7>] (of_iommu_configure+0x127/0x150)
>> [    0.328896] [<c052e6d7>] (of_iommu_configure) from [<c073f697>] (of_dma_configure_id+0x1fb/0x2ec)
>> [    0.329060] [<c073f697>] (of_dma_configure_id) from [<c059743f>] (really_probe+0x7b/0x2a0)
>> [    0.331438] tegra-dc 54200000.dc: --------tegra_smmu_probe_device, 822
>> [    0.332234] [<c052ebed>] (tegra_smmu_probe_device) from [<c052bd6d>] (__iommu_probe_device+0x35/0x1c4)
>> [    0.332391] [<c052bd6d>] (__iommu_probe_device) from [<c052c3cd>] (iommu_probe_device+0x19/0xec)
>> [    0.332545] [<c052c3cd>] (iommu_probe_device) from [<c052e6ab>] (of_iommu_configure+0xfb/0x150)
>> [    0.332701] [<c052e6ab>] (of_iommu_configure) from [<c073f697>] (of_dma_configure_id+0x1fb/0x2ec)
>> [    0.332804] [<c073f697>] (of_dma_configure_id) from [<c059743f>] (really_probe+0x7b/0x2a0)
>> [    0.335202] tegra-dc 54200000.dc: ---------iommu_group_get_for_dev, 1572
>> [    0.335292] tegra-dc 54200000.dc: ---------tegra_smmu_device_group, 862
>> [    0.335474] tegra-dc 54200000.dc: ---------tegra_smmu_device_group, 909: 1: drm
>> [    0.335566] tegra-dc 54200000.dc: ---------iommu_group_get_for_dev, 1574
>> [    0.335718] tegra-dc 54200000.dc: ---------iommu_group_add_device, 858
>> [    0.335862] tegra-dc 54200000.dc: Adding to iommu group 1
>> [    0.335955] tegra-dc 54200000.dc: ---------iommu_alloc_default_domain, 1543: type 3
>> [    0.336101] iommu: ------iommu_group_alloc_default_domain: platform, (null), drm
>> [    0.336187] ---------tegra_smmu_domain_alloc, 284: type 3
>  [    0.336968] [<c0a0ff45>] (tegra_smmu_domain_alloc) from [<c0a0f87b>] (iommu_group_alloc_default_domain+0x4b/0xfa)
>> [    0.337127] [<c0a0f87b>] (iommu_group_alloc_default_domain) from [<c052c41d>] (iommu_probe_device+0x69/0xec)
>> [    0.337285] [<c052c41d>] (iommu_probe_device) from [<c052e6ab>] (of_iommu_configure+0xfb/0x150)
>> [    0.337441] [<c052e6ab>] (of_iommu_configure) from [<c073f697>] (of_dma_configure_id+0x1fb/0x2ec)
>> [    0.337599] [<c073f697>] (of_dma_configure_id) from [<c059743f>] (really_probe+0x7b/0x2a0)
>> [    0.339913] tegra-dc 54200000.dc: ---------iommu_probe_device, 272
>> [    0.348144] tegra-dc 54200000.dc: failed to probe RGB output: -517
> 
> Hmm..not sure where this EPROBE_DEFER comes from.

DC driver on Nexus 7 depends on LVDS bridge and display panel, which
cause the probe defer.

> But you are right,
> as of_dma_configure_id() returns because of that so it didn't run to
> arch_setup_dma_ops() call, which allocates an UNMANAGED iommu domain
> and attaches DC to it on Tegra124.
> 
> By the way, anyone can accept this change? It doesn't feel right to
> leave a regression in the newer release...
> 

I think Thierry should give ack.