Re: [PATCH v10 00/17] drm/exynos: atomic modesetting support

[Inki Dae <inki.dae@samsung.com>]

On 2015년 06월 10일 20:38, Marek Szyprowski wrote:
> Hello,
> 
> On 2015-06-10 12:59, Inki Dae wrote:
>> Hi Marek,
>>
>> On 2015년 06월 10일 19:03, Marek Szyprowski wrote:
>>> Hello,
>>>
>>> On 2015-06-01 17:04, Gustavo Padovan wrote:
>>>> From: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
>>>>
>>>> Hi,
>>>>
>>>> Here goes the full support for atomic modesetting on exynos. I've
>>>> split the patches in the various phases of atomic support.
>>> Thanks for this patchses, however I've noticed a problem after applying
>>> them.
>>> The issue gets revealed when support for IOMMU is enabled. I've did my
>>> tests
>>> with Exynos HDMI driver on Odroid U3 board.
>>>
>>> To demonstrated the issue I've added following additional debug in the
>>> exynos
>>> mixer driver in mixer_graph_buffer() function:
>>> pr_info("dma addr %pad plane->src_width %d plane->src_height %d\n",
>>> &plane->dma_addr[0], plane->src_width, plane->src_height);
>>>
>>> Before applying patches setting 640x480 mode and getting back to
>>> 1920x1080
>>> console generates following log:
>>>
>>> # modetest -M exynos -s 23:640x480
>>> setting mode 640x480-60Hz@XR24 on connectors 23, crtc 21
>>> [ 3860.617151] dma 0xbc500000 plane->src_width 640 plane->src_height 480
>>> ^C
>>> [ 3870.555232] dma 0xbbd00000 plane->src_width 1920 plane->src_height
>>> 1080
>>> [ 3870.565696] dma 0xbbd00000 plane->src_width 1920 plane->src_height
>>> 1080
>>>
>>> After applying atomic modesetting patchset:
>>> # modetest -M exynos -s 24:640x480
>>> [  142.540122] dma 0xbbd00000 plane->src_width 1920 plane->src_height
>>> 1080
>>> [  142.550726] dma 0xbbd00000 plane->src_width 1920 plane->src_height
>>> 1080
>>> setting mode 640x480-60Hz@XR24 on connectors 24, crtc 22
>>> [  142.643672] dma 0xbc500000 plane->src_width 1920 plane->src_height
>>> 1080
>>> [  142.759982] dma 0xbc500000 plane->src_width 640 plane->src_height 480
>>> ^C
>>> [  154.986040] dma 0xbbd00000 plane->src_width 1920 plane->src_height
>>> 1080
>>>
>>> As you can see from the above log, mixer_graph_buffer function is called
>>> several times. 0xbbd00000 is the DMA address of the 1920x1080
>>> framebuffer
>>> and 0xbc500000 is the DMA address of the allocated 640x480 buffer.
>>> mixer_graph_buffer() is first called with the new DMA address of the
>>> framebuffer, but with the old mode parameters (1920x1080 size) and then
>>> in the next call it updates the plane parameters to the correct values
>>> (size changed to 640x480). When IOMMU is not used, this can be easily
>>> missed, but after enabling IOMMU support, any DMA access to unallocated
>>> address causes IOMMU PAGE FAULT. Here it will happen after changing DMA
>>> address of the buffer without changing the size.
>>>
>>> A quick workaround to resolve this multiple calls to
>>> mixer_graph_buffer()
>>> with partially updated mode values is to remove calls to
>>> mixer_window_suspend/mixer_window_resume from mixer_disable and
>>> mixer_disable functions, but I expect that this is not the right
>>> approach.
>>>
>>> Probably the same problem can be observed with Exynos FIMD driver.
>>>
>>> Gustavo: could you check if mixer_enable functions should really
>>> call mixer_window_resume function, which in turn calls mixer_win_commit,
>>> which calls mixer_graph_buffer with partially updated display buffer
>>> data?
>> Marek, can you share how other people can test the atomic feature with
>> iommu?
>>
>> I should have merged below several patches and added device tree
>> relevant codes to test iommu.
>>
>> 1. Merged iommu support patches for Exynos SoC below iommu exynos tree,
>>
>> https://git.kernel.org/cgit/linux/kernel/git/joro/iommu.git/log/?h=arm/exynos
>>
>>
>> 2. Merged below patch,
>>      [PATCH v7 24/25] ARM: DMA-mapping: add
>> support for creating reserved mappings in iova space
>>
>> 3. Added device node relevant codes - I tested Exynos drm on trats2
>> board based on Exynos4412 SoC - like below,
>> in exynos4.dtsi file:
>> fimd: fimd@11c00000 {
>>                   ...
>>                 iommus = <&sysmmu_fimd0>;
>>                   ...
>>
>> sysmmu_fimd0: sysmmu@11E20000 {
>>          compatible = "samsung,exynos-sysmmu";
>>          reg = <0x11E20000 0x1000>;
>>          interrupt-parent = <&combiner>;
>>          interrupts = <5 2>;
>>          clock-names = "sysmmu", "master";
>>          clocks = <&clock CLK_SMMU_FIMD0>, <&clock CLK_FIMD0>;
>>           power-domains = <&pd_lcd0>;
>>          #iommu-cells = <0>;
>> };
>>
>> in exynos4412-trats2.dts file:
>> fimd@11c00000 {
>>                  status = "okay";
>>                  iommu-reserved-mapping = <0x40000000 0x40000000
>> 0x40000000>;
>> };
>>
>> Is that all? You would need to share exact guide about iommu enabling to
>> other people so that they can test atomic feature with iommu.
> 
> Right, the above should be enough. For convenience I've prepared a
> branch with all needed patches:
> https://git.linaro.org/people/marek.szyprowski/linux-srpol.git
> v4.1-exynos-drm-iommu
> 
> I've included following branches:
> https://git.kernel.org/cgit/linux/kernel/git/daeinki/drm-exynos.git/log/?h=exynos-drm/for-next
> 
> https://git.kernel.org/cgit/linux/kernel/git/kgene/linux-samsung.git/log/?h=v4.2-next/dt-samsung-4th
> 
> https://git.kernel.org/cgit/linux/kernel/git/kgene/linux-samsung.git/log/?h=v4.2-next/mach-samsung
> 
> https://git.kernel.org/cgit/linux/kernel/git/joro/iommu.git/log/?h=arm/exynos
> 
> 
> Then I've applied my Exynos DRM patches
> (http://www.spinics.net/lists/linux-samsung-soc/msg45114.html)
> as well as rebased patch 24/25 and 25/25 from my initial v7 IOMMU series
> (http://www.spinics.net/lists/linux-samsung-soc/msg44652.html).
> 

Thanks, Marek.

Gustavo and Joonyoung, let's resolve the page fault issue with iommu
this time. I'd like to merge most patch sets - atomic feature, iommu,
Exynos5433 IP support, and driver initialization consolidating. I should
have pull-request in the near feature. So we need to do this in a hurry.

Thanks,
Inki Dae

> Best regards

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