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Subject: Re: [PATCH v1 2/2] iommu/tegra-smmu: Revert workaround that was
 needed for Nyan Big Chromebook
To:     Guillaume Tucker <guillaume.tucker@collabora.com>,
        Nicolin Chen <nicoleotsuka@gmail.com>
Cc:     Thierry Reding <thierry.reding@gmail.com>,
        Joerg Roedel <joro@8bytes.org>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        Krishna Reddy <vdumpa@nvidia.com>,
        Will Deacon <will@kernel.org>,
        iommu@lists.linux-foundation.org, linux-tegra@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20210328233256.20494-1-digetx@gmail.com>
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 <20210401085549.GA31146@Asurada-Nvidia>
 <50a7e4c7-0e72-534a-a317-366e455213c1@gmail.com>
 <d01ccde4-5fa9-2aa7-c28b-b3899cc54c54@collabora.com>
From:   Dmitry Osipenko <digetx@gmail.com>
Message-ID: <724e683f-5317-cdf7-7351-fcfd42b7b607@gmail.com>
Date:   Fri, 23 Apr 2021 18:23:22 +0300
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23.04.2021 18:01, Guillaume Tucker пишет:
> On 02/04/2021 15:40, Dmitry Osipenko wrote:
>> 01.04.2021 11:55, Nicolin Chen пишет:
>>> On Mon, Mar 29, 2021 at 02:32:56AM +0300, Dmitry Osipenko wrote:
>>>> The previous commit fixes problem where display client was attaching too
>>>> early to IOMMU during kernel boot in a multi-platform kernel configuration
>>>> which enables CONFIG_ARM_DMA_USE_IOMMU=y. The workaround that helped to
>>>> defer the IOMMU attachment for Nyan Big Chromebook isn't needed anymore,
>>>> revert it.
>>>
>>> Sorry for the late reply. I have been busy with downstream tasks.
>>>
>>> I will give them a try by the end of the week. Yet, probably it'd
>>> be better to include Guillaume also as he has the Nyan platform.
>>>
>>
>> Indeed, thanks. Although, I'm pretty sure that it's the same issue which
>> I reproduced on Nexus 7.
>>
>> Guillaume, could you please give a test to these patches on Nyan Big?
>> There should be no EMEM errors in the kernel log with this patches.
>>
>> https://patchwork.ozlabs.org/project/linux-tegra/list/?series=236215
> 
> So sorry for the very late reply.  I have tried the patches but
> hit some issues on linux-next, it's not reaching a login prompt
> with next-20210422.  So I then tried with next-20210419 which
> does boot but shows the IOMMU error:
> 
> <6>[    2.995341] tegra-dc 54200000.dc: Adding to iommu group 1
> <4>[    3.001070] Failed to attached device 54200000.dc to IOMMU_mapping  
> 
>   https://lava.collabora.co.uk/scheduler/job/3570052#L1120
> 
> The branch I'm using with the patches applied can be found here:
> 
>   https://gitlab.collabora.com/gtucker/linux/-/commits/next-20210419-nyan-big-drm-read/
> 
> Hope this helps, let me know if you need anything else to be
> tested.


Hello Guillaume,

The current linux-next doesn't boot on all ARM (AFAIK), the older
next-20210413 works. The above message should be unrelated to the boot
problem. It should be okay to ignore that message as it should be
harmless in yours case.