Re: Linux-next, Exynos Octa boot fail, bisected to: "drm/exynos: remove drm_iommu_attach_device_if_possible"

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

On 2015년 07월 22일 19:08, Inki Dae wrote:
> On 2015년 07월 22일 17:42, Joonyoung Shim wrote:
>> On 07/22/2015 05:22 PM, Inki Dae wrote:
>>> On 2015년 07월 22일 17:12, Joonyoung Shim wrote:
>>>> On 07/22/2015 01:55 PM, Inki Dae wrote:
>>>>> On 2015년 07월 22일 11:02, Joonyoung Shim wrote:
>>>>>> On 07/21/2015 10:19 PM, Krzysztof Kozlowski wrote:
>>>>>>> Hi,
>>>>>>>
>>>>>>> Today's linux-next (next-20150721) encounters boot failures on Exynos
>>>>>>> Octa (Exynos5422) based boards. The boards hangs. I bisected it to:
>>>>>>>
>>>>>>> d80167b85024982c5f18d0481a5c248100360118 is the first bad commit
>>>>>>> commit d80167b85024982c5f18d0481a5c248100360118
>>>>>>> Author: Joonyoung Shim <jy0922.shim@samsung.com>
>>>>>>> Date:   Thu Jul 2 21:49:39 2015 +0900
>>>>>>>
>>>>>>>     drm/exynos: remove drm_iommu_attach_device_if_possible
>>>>>>>
>>>>>>>     Already drm_iommu_attach_device checks whether support iommu internally.
>>>>>>>     It should clear channels always regardless iommu support. We didn't know
>>>>>>>     because we can detect the problem when iommu is enabled, so we don't
>>>>>>>     have to use drm_iommu_attach_device_if_possible and then we can remove
>>>>>>>     drm_iommu_attach_device_if_possible and clear_channels function pointer.
>>>>>>>
>>>>>>>     Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
>>>>>>>     Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
>>>>>>>     Signed-off-by: Inki Dae <inki.dae@samsung.com>
>>>>>>>
>>>>>>> :040000 040000 83379efbf4960f58d680371628ec04387935bd53
>>>>>>> da03c338b88e7cb6bda895b3dd52d78d9b6eba30 M drivers
>>>>>>>
>>>>>>>
>>>>>>> Config: exynos
>>>>>>> Boot log from Odroid XU3-Lite attached.
>>>>>>>
>>>>>>> Any hints or ideas?
>>>>>>
>>>>>> The point that hangs is when accesses fimd register in
>>>>>> fimd_clear_channels function, so i doubt clock setting for fimd.
>>>>>>
>>>>>> It's gone something that hangs after i enable gating for ACLK_200_DISP1
>>>>>> clock.
>>>>>>
>>>>>> If ACLK_200_DISP1 clock needs for fimd really, i'm thinking how can it
>>>>>> support. Any ideas?
>>>>>
>>>>> I think bootloader should have enabled ACLK_200_DISP1 clock and also
>>>>> device driver should enable all relevant clocks before the device
>>>>> accesses its own registers.
>>>>>
>>>>> Best way would be that the clock is enabled by common clock framework
>>>>> but it seems there is no anything that the clock framework can do it. So
>>>>> I think what we have to do is to add the clock support to device tree.
>>>>
>>>> It's not easy problem to me. Should we add which clock? I think we
>>>> cannot control ACLK_200_DISP1 or CLKDIV2_DISP1_BLK directly by below
>>>> hierarchy, right? Then we should control gate clocks, but we have not
>>>> controlled any gate clocks using BTS_ prefix.
>>>>
>>>> The clock hierarchy from Exynos5422 user manual,
>>>> ACLK_200_DISP1 -- CLKDIV2_DISP1_BLK -- HDMI LINK
>>>>                                        HDMI PHY
>>>>                                        MIC1
>>>>                                        DSIM1
>>>>                                        DPTX LINK
>>>>                                        MDNIE1
>>>>                                        SYSMMU_MIXER
>>>>                                        SYSMMU_FIMD1_M0
>>>>                                        SYSMMU_FIMD1_M1
>>>>                                        BTS_TVM0
>>>>                                        BTS_TVM1
>>>>                                        BTS_FIMD1_M0
>>>>                                        BTS_FIMD1_M1
>>>>
>>>> Other way, IMHO, fimd driver doesn't have to enable ACLK_200_DISP1 clock,
>>>> just it should be controlled by connector drivers, e.g. dsi, dp because
>>>> fimd only cannot operate, so dsi or dp must need (Actually i'm not sure
>>>> about this, just i thought that Exynos5 SoCs don't have any gpios for
>>>> dpi, so they cannot use dpi, right?).
>>>>
>>>> It needs to probe connector driver like dsi or dp earlier than fimd and
>>>> fimd_bind function should return error if connector driver like dsi or
>>>> dp was not probed. This is also not easy to me.
>>>
>>> In this case, if one of above gate clocks is enabled, the ACLK_200_DISP1
>>> should be enabled. So I guess the problem would be due to below line of
>>> clk-exynos5420.c,
>>>
>>> GATE(CLK_FIMD1, "fimd1", "aclk300_disp1", GATE_IP_DISP1, 0, 0, 0),
>>>
>>> Can you check it again after modifying it like below?,
>>> GATE(CLK_FIMD1, "fimd1", "aclk200_disp1", GATE_IP_DISP1, 0, 0, 0),
>>
>> No, parent clock of fimd1 gate clock is ACLK_300_DISP1.
> 
> Yes, I checked just it through exynos5420 and exynos5422 document. I
> just guessed. So do you mean that aclk200_disp1 affects FIMD controller
> even though aclk200_disp1 isn't a parent clock of FIMD? If so, it's very
> strange.

Root problem was because it had tried to access FIMD registers before
crtc and connector driver binding is completed.

ACLK200_DISP1 will be enabled by connector driver - MIPI-DSI - of FIMD
like above clock hierarchy commented by Joonyoung.

So all we have to do would be,
1. to put off clearing channel and attaching iommu just after the
binding completion between crtc and connector drivers - in case of
Exynos drm driver, the binding is done before modeset operation.

Or 2. to enable FIMD relevant clock gates, BTS_FIMD1_M0/1 in FIMD driver.

In case of number 1, we would need to add a new interface which can
notify that crtc drivers enable their iommu units just after the binding
completion.

In case of number 2, it would mean we should consider to enable relevant
clock gates for other crtc drivers - decon drivers for Exynos5433 and
Exynos7.

I tend to proper number 2 because it's easier way than number 1.

Thanks,
Inki Dae

> 
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