linux-kernel - Re: [PATCH v1 2/2] iommu/tegra-smmu: Revert workaround that was needed for Nyan Big Chromebook

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Date:   Fri, 23 Apr 2021 16:01:06 +0100
From:   Guillaume Tucker <guillaume.tucker@...labora.com>
To:     Dmitry Osipenko <digetx@...il.com>,
        Nicolin Chen <nicoleotsuka@...il.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Joerg Roedel <joro@...tes.org>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Krishna Reddy <vdumpa@...dia.com>,
        Will Deacon <will@...nel.org>,
        iommu@...ts.linux-foundation.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 2/2] iommu/tegra-smmu: Revert workaround that was
 needed for Nyan Big Chromebook

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.

Best wishes,
Guillaume