On 08/12/2016 11:28 AM, Shuah Khan wrote:
> On 08/10/2016 05:05 PM, Shuah Khan wrote:
>> 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
>
> Hi Inki,
>
> I am looking into this further and I am finding inconsistent
> commits with regards to GEM contiguous and non-contiguous
> buffers.
>
> Okay what you said is that:
>
> exymod-drm should support non-continguous and contiguous GEM memory
> type with or without IOMMU
>
> However, the code currently isn't doing that. The following
> commit allocates non-contiguous buffers when IOMMU is enabled
> to handle contiguous allocation failures.
>
> There are other commits that removed checks for non-contig type.
> Let's look at the following cases to see what should be the driver
> behavior in these cases:
>
> IOMMU is disabled:
>
> exynos_drm_gem_create_ioctl() gets called with NONCONTIG
> - driver should try to allocate non-contig
> - if it can't allocate non-contig, allocate contig
> ( this will allow avoid failure like the one I am seeing)
>
> exynos_drm_gem_create_ioctl() gets called with CONTIG
> - driver should try to allocate contig
> - if it can't allocate contig, allocate non-contig
>
> What is confusing is there are several code paths in the
> GEN allocation and checking memory types are enforcing
> non-contig with IOMMU. Check this routine:
>
> exynos_drm_framebuffer_init() will reject non-contig
> memory type when check_fb_gem_memory_type() rejects
> non-contig GEM memory type without IOMMU.
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
Anyway, if it is th right change to fix check_fb_gem_memory_type()
to not reject NONCONTIG_BUFFER, then I can make that change
instead of this patch I sent.
>
> So there is inconsistency in the non-contig vs. contig
> GEM support in exynos-drm. I think this needs to be cleaned
> up to get the desired behavior.
>
> The following commit allocates non-contiguous buffers when IOMMU is
> enabled to handle contiguous allocation failures.
>
> There are other commits that removed checks for non-contig type.
> Let's look at the following cases to see what should be the driver
> behavior in these cases:
>
> commit 122beea84bb90236b1ae545f08267af58591c21b
> Author: Rahul Sharma <Rahul.Sharma@xxxxxxxxxxx>
> Date: Wed May 7 17:21:29 2014 +0530
>
> drm/exynos: allocate non-contigous buffers when iommu is enabled
>
> Allow to allocate non-contigous buffers when iommu is enabled.
> Currently, it tries to allocates contigous buffer which consistently
> fail for large buffers and then fall back to non contigous. Apart
> from being slow, this implementation is also very noisy and fills
> the screen with alloc fail logs.
>
> Signed-off-by: Rahul Sharma <Rahul.Sharma@xxxxxxxxxxx>
> Reviewed-by: Sachin Kamat <sachin.kamat@xxxxxxxxxx>
> Signed-off-by: Inki Dae <inki.dae@xxxxxxxxxxx>
>
>
> commit ea6d66c3a797376d21b23dc8261733ce35970014
> Author: Inki Dae <inki.dae@xxxxxxxxxxx>
> Date: Fri Nov 2 16:10:39 2012 +0900
>
> drm/exynos: remove EXYNOS_BO_NONCONTIG type checking.
>
> With iommu support, non-continuous buffer also is supported so
> this patch removes these checking from exynos_drm_gem_get/put_dma_addr
> funciton.
>
> This patch is based on the below patch set, "drm/exynos: add
> iommu support for -next".
> http://www.spinics.net/lists/dri-devel/msg29041.html
>
> Signed-off-by: Inki Dae <inki.dae@xxxxxxxxxxx>
> Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
>
> commit 2b35892e9da672df40ce890bffc4f9f6119c57e0
> Author: Inki Dae <inki.dae@xxxxxxxxxxx>
> Date: Fri Mar 16 18:47:05 2012 +0900
>
> drm/exynos: update gem and buffer framework.
>
> with this patch, we can allocate physically continuous or non-continuous
> memory and also it creates scatterlist for iommu support so allocated
> memory region can be mapped to iommu page table using scatterlist.
>
> Signed-off-by: Inki Dae <inki.dae@xxxxxxxxxxx>
> Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
> Signed-off-by: Dave Airlie <airlied@xxxxxxxxxx>
>
> -- Shuah
>
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