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

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Date:	Wed, 22 Jul 2015 13:55:11 +0900
From:	Inki Dae <inki.dae@...sung.com>
To:	Joonyoung Shim <jy0922.shim@...sung.com>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Seung-Woo Kim <sw0312.kim@...sung.com>
Cc:	dri-devel@...ts.freedesktop.org,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Kukjin Kim <kgene@...nel.org>,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
	Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: Linux-next, Exynos Octa boot fail,
 bisected to: "drm/exynos: remove drm_iommu_attach_device_if_possible"

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@...sung.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@...sung.com>
>>     Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>
>>     Signed-off-by: Inki Dae <inki.dae@...sung.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.

Other idea?

Thanks,
Inki Dae

> 
> Thanks.
> --
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