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

Inki Dae
2015-06-10T10:59:46Z

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.

Thanks,
Inki Dae

>
>> (...)
>
> Best regards