Re: [PATCH] exynos-drm: Fix display manager failing to start without IOMMU problem
From: Shuah Khan
Date: Wed Oct 12 2016 - 19:15:56 EST
On 10/12/2016 05:11 PM, Shuah Khan wrote:
+ Fixing Krzysztof Kozlowski address.
> Hi Inki,
> On 08/15/2016 10:40 PM, Inki Dae wrote:
>>> okay the very first commit that added IOMMU support
>>> introduced the code that rejects non-contig gem memory
>>> type without IOMMU.
>>> commit 0519f9a12d0113caab78980c48a7902d2bd40c2c
>>> Author: Inki Dae <inki.dae@xxxxxxxxxxx>
>>> Date: Sat Oct 20 07:53:42 2012 -0700
>>> drm/exynos: add iommu support for exynos drm framework
> I haven't given up on this yet. I am still seeing the following failure:
> Additional debug messages I added:
> [ 15.287403] exynos_drm_gem_create_ioctl() 1
> [ 15.287419] exynos_drm_gem_create() flags 1
> [ 15.311511] [drm:exynos_drm_framebuffer_init] *ERROR* Non-contiguous GEM memory is not supported.
> Additional debug message I added:
> [ 15.318981] [drm:exynos_user_fb_create] *ERROR* failed to initialize framebuffer
> This is what happens:
> 1. exynos_drm_gem_create_ioctl() gets called with EXYNOS_BO_NONCONTIG request
> 2. exynos_drm_gem_create(0 goes ahead and creates the GEM buffers
> 3. exynos_user_fb_create() tries to associate GEM to fb and fails during
> At this point, there is no recovery and lightdm fails
> xf86-video-armsoc/src/drmmode_exynos/drmmode_exynos.c assumes contiguous
> allocations are not supported in some exynos drm versions: The following
> commit introduced this change:
> excerpts from the diff:- if (create_gem->buf_type == ARMSOC_BO_SCANOUT)
> - create_exynos.flags = EXYNOS_BO_CONTIG;
> - else
> - create_exynos.flags = EXYNOS_BO_NONCONTIG;
> + /* Contiguous allocations are not supported in some exynos drm versions.
> + * When they are supported all allocations are effectively contiguous
> + * anyway, so for simplicity we always request non contiguous buffers.
> + */
> + create_exynos.flags = EXYNOS_BO_NONCONTIG;
> There might have been logic on exynos_drm that forced Contig when it coudn't
> support NONCONTIG. At least, that is what this comment suggests. This assumption
> doesn't appear to be a good one and not sure if this change was made to fix a bug.
> After the IOMMU support, this assumption is no longer true. Hence, with IOMMU
> support, latest kernels have a mismatch with the installed xf86-video-armsoc
> This is what I am running into. This leads to the following question:
> 1. How do we ensure exynos_drm kernel changes don't break user-space
> specifically xf86-video-armsoc
> 2. This seems to have gone undetected for a while. I see a change in
> exynos_drm_gem_dumb_create() that is probably addressing this type
> of breakage. Commit 122beea84bb90236b1ae545f08267af58591c21b adds
> handling for IOMMU NONCONTIG case.
> Anyway, I am interested in getting the exynos_drm kernel side code
> and xf86-video-armsoc in sync to resolve the issue.
> Could you recommend a going forward plan?
> I can submit a patch to xf86-video-armsoc. I am also looking ahead to
> see if we can avoid such breaks in the future by keeping kernel and
> xf86-video-armsoc in sync.
> -- Shuah