Re: [PATCH 14/15] media: s5p-mfc: Use preallocated block allocator always for MFC v6+

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On 02/27/2017 05:50 AM, Marek Szyprowski wrote:
> Hi Shuah,
> 
> On 2017-02-24 15:23, Shuah Khan wrote:
>> On Thu, Feb 23, 2017 at 11:26 PM, Marek Szyprowski
>> <m.szyprowski@xxxxxxxxxxx> wrote:
>>> On 2017-02-23 22:43, Shuah Khan wrote:
>>>> On Tue, Feb 14, 2017 at 12:52 AM, Marek Szyprowski
>>>> <m.szyprowski@xxxxxxxxxxx> wrote:
>>>>> It turned out that all versions of MFC v6+ hardware doesn't have a strict
>>>>> requirement for ALL buffers to be allocated on higher addresses than the
>>>>> firmware base like it was documented for MFC v5. This requirement is true
>>>>> only for the device and per-context buffers. All video data buffers can
>>>>> be
>>>>> allocated anywhere for all MFC v6+ versions. Basing on this fact, the
>>>>> special DMA configuration based on two reserved memory regions is not
>>>>> really needed for MFC v6+ devices, because the memory requirements for
>>>>> the
>>>>> firmware, device and per-context buffers can be fulfilled by the simple
>>>>> probe-time pre-allocated block allocator instroduced in previous patch.
>>>>>
>>>>> This patch enables support for such pre-allocated block based allocator
>>>>> always for MFC v6+ devices. Due to the limitations of the memory
>>>>> management
>>>>> subsystem the largest supported size of the pre-allocated buffer when no
>>>>> CMA (Contiguous Memory Allocator) is enabled is 4MiB.
>>>>>
>>>>> This patch also removes the requirement to provide two reserved memory
>>>>> regions for MFC v6+ devices in device tree. Now the driver is fully
>>>>> functional without them.
>>>>>
>>>>> Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
>>>> Hi Marek,
>>>>
>>>> This patch breaks display manager. exynos_drm_gem_create() isn't happy.
>>>> dmesg and console are flooded with
>>>>
>>>> odroid login: [  209.170566] [drm:exynos_drm_gem_create] *ERROR* failed to
>>>> allo.
>>>> [  212.173222] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>> [  215.354790] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>> [  218.736464] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>> [  221.837128] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>> [  226.284827] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>> [  229.242498] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>> [  232.063150] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>> [  235.799993] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>> [  239.472061] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>> [  242.567465] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>> [  246.500541] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>> [  249.996018] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>> [  253.837272] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>> [  257.048782] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>> [  260.084819] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>> [  263.448611] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>> [  266.271074] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>> [  269.011558] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>> [  272.039066] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>> [  275.404938] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>> [  278.339033] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>> [  281.274751] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>> [  284.641202] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>> [  287.461039] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>> [  291.062011] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>> [  294.746870] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>> [  298.246570] [drm:exynos_drm_gem_create] *ERROR* failed to allocate
>>>> buffer.
>>>>
>>>> I don't think this is an acceptable behavior. It is a regression.
>>>
>>> This is a really poor bug report... Could you elaborate a bit how to
>>> reproduce
>>> this? Could you provide your kernel config and information about test
>>> environment?
>> Yeah. I should have give you more information. My bad.
>>
>>> I suspect that you use CMA without IOMMU and you have too small global CMA
>>> region.
>> Yes. I have CMA and using exynos_defconfig. Nothing fancy. I think
>> what's happening is s5p_mfc pre-allocates and there is nothing left
>> when disaply manager starts requestuing gem buffers. This failure
>> happens when systemd kicks off lightdm.
>>
>>> After this patch MFC driver uses global CMA region instead of the MFC's
>>> private
>>> ones, so one has to ensure that the global region is large enough.
>> This is still a regression since it requires users to take some
>> action. I think we need some kind of checks to warn users there isn't
>> a large enough CMA region. This is the same config I have been using
>> forever and with this patch, it breaks.
>>
>> Easy to reproduce on odroid-xu4 with HDMI display. You just have to
>> boot the system with exynos_defconfig. Display manager will fail when
>> it requests buffers.
> 
> That is still a bit strange. MFC pre-allocates 8MiB buffer. The default CMA
> global region size is 64MiB, which should be enough for a few display buffers.
> It looks that your display manager consumes quite a lot of memory and it
> already almost hits the limit from the exynos_defconfig.
> 
> It should be safe to increase default CMA region size to 80MiB or even 96MiB
> in the exynos_defconfig to avoid such problem.

Increasing CONFIG_CMA_SIZE_MBYTES to 96 in exynos_defconfig worked for me.
No more gem buffer allocation errors. I sent in a patch to exynos_defconfig
with your Suggested-by

thanks,
-- Shuah
> 
> Best regards

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