Re: [PATCH] drm/exynos: IOMMU support should not be selectable by user

[Tobias Jakobi <liquid.acid@gmx.net>]

Hello!

Marek Szyprowski wrote:
> If system provides IOMMU feature, Exynos DRM should use it by default,
> because the Exynos DRM subdrivers don't work correctly when Exynos IOMMU
> driver has been enabled and no IOMMU support has been compiled into Exynos
> DRM driver.
> 
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> ---
>  drivers/gpu/drm/exynos/Kconfig | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/exynos/Kconfig b/drivers/gpu/drm/exynos/Kconfig
> index 7f9f6f9e9b7e..39fe490efcd4 100644
> --- a/drivers/gpu/drm/exynos/Kconfig
> +++ b/drivers/gpu/drm/exynos/Kconfig
> @@ -13,10 +13,9 @@ config DRM_EXYNOS
>  	  If M is selected the module will be called exynosdrm.
>  
>  config DRM_EXYNOS_IOMMU
> -	bool "EXYNOS DRM IOMMU Support"
> +	bool
>  	depends on DRM_EXYNOS && EXYNOS_IOMMU && ARM_DMA_USE_IOMMU
> -	help
> -	  Choose this option if you want to use IOMMU feature for DRM.
> +	default y
>  
>  config DRM_EXYNOS_DMABUF
>  	bool "EXYNOS DRM DMABUF"
> 

I tested Exynos DRM with the IOMMU enabled today and couldn't find any
of the previous issues.

A few things that I noticed though:

1) Without the IOMMU I get these powerdomain infos in the kernel logs:
"lcd0-power-domain: Power-on latency exceeded, new value 416167 ns"
"tv-power-domain: Power-on latency exceeded, new value 456125 ns"
These don't appear with the IOMMU, so I was wondering if the
powerdomains are now staying on the whole time?

2) With Exynos DRM now having a dependency on IOMMU (when it is
enabled), I was wondering if anything needs to be done for the old
's5p-tv' driver to work properly now?

With best wishes,
Tobias

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