linux-kernel - Re: [PATCH] exynos-drm: Fix display manager failing to start without IOMMU problem

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Message-ID: <57ABB31E.1070802@osg.samsung.com>
Date:	Wed, 10 Aug 2016 17:05:02 -0600
From:	Shuah Khan <shuahkh@....samsung.com>
To:	Inki Dae <inki.dae@...sung.com>, jy0922.shim@...sung.com,
	sw0312.kim@...sung.com, kyungmin.park@...sung.com,
	airlied@...ux.ie, kgene@...nel.org, k.kozlowski@...sung.com
Cc:	dri-devel@...ts.freedesktop.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
	Shuah Khan <shuahkh@....samsung.com>
Subject: Re: [PATCH] exynos-drm: Fix display manager failing to start without
 IOMMU problem

On 08/10/2016 04:59 PM, Inki Dae wrote:
> Hi Shuah,
> 
> 2016년 08월 11일 02:30에 Shuah Khan 이(가) 쓴 글:
>> Fix exynos_drm_gem_create_ioctl() attempts to allocate non-contiguous GEM
>> memory without IOMMU. In this case, there is no point in attempting to
> 
> DRM gem can be used for Non-DRM drivers such as GPU, V4L2 based Multimedia device and other DMA devices.
> Even though IOMMU support is disabled, other framework based DMA drivers can use IOMMU - i.e., GPU driver -
> and they can use non-contiguous GEM buffer through UMM. (DMABUF) 
> 
> So GEM allocation type is not dependent on IOMMU.

Hi Inki,

I am seeing the following failure without IOMMU and light dm fails
to start:

[drm:exynos_drm_framebuffer_init] *ERROR* Non-continguous GEM memory is not supported.

The change I made fixed that problem and light dm starts without IOMMU.
Is there a better way to fix this problem? Currently without IOMMU,
light dm doesn't start.

This is on linux_next

thanks,
-- Shuah