linux-kernel - Re: [PATCH] memory: tegra: Remove GPU from DRM IOMMU group

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Date:   Tue, 1 Sep 2020 19:57:52 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Krzysztof Kozlowski <krzk@...nel.org>
Cc:     Jonathan Hunter <jonathanh@...dia.com>,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
        Matias Zuniga <matias.nicolas.zc@...il.com>
Subject: Re: [PATCH] memory: tegra: Remove GPU from DRM IOMMU group

01.09.2020 18:32, Thierry Reding пишет:
> From: Thierry Reding <treding@...dia.com>
> 
> Commit 63a613fdb16c ("memory: tegra: Add gr2d and gr3d to DRM IOMMU
> group") added the GPU to the DRM IOMMU group, which doesn't make any
> sense. This causes problems when Nouveau tries to attach to the SMMU
> and causes it to fall back to using the DMA API.
> 
> Remove the GPU from the DRM groups to restore the old behaviour. The
> GPU should always have its own IOMMU domain to make sure it can map
> buffers into contiguous chunks (for big page support) without getting
> in the way of mappings from the DRM group.
> 
> Fixes: 63a613fdb16c ("memory: tegra: Add gr2d and gr3d to DRM IOMMU group")
> Reported-by: Matias Zuniga <matias.nicolas.zc@...il.com>
> Signed-off-by: Thierry Reding <treding@...dia.com>
> ---
>  drivers/memory/tegra/tegra124.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/memory/tegra/tegra124.c b/drivers/memory/tegra/tegra124.c
> index 493b5dc3a4b3..0cede24479bf 100644
> --- a/drivers/memory/tegra/tegra124.c
> +++ b/drivers/memory/tegra/tegra124.c
> @@ -957,7 +957,6 @@ static const struct tegra_smmu_swgroup tegra124_swgroups[] = {
>  static const unsigned int tegra124_group_drm[] = {
>  	TEGRA_SWGROUP_DC,
>  	TEGRA_SWGROUP_DCB,
> -	TEGRA_SWGROUP_GPU,
>  	TEGRA_SWGROUP_VIC,
>  };
>  
> 

Technically a stable tag is needed for this patch, but I guess the bot
will recognize that this patch is useful for older kernels.

Otherwise looks good!

Reviewed-by: Dmitry Osipenko <digetx@...il.com>