linux-kernel - Re: [PATCH 1/1] ARM: exynos_defconfig: Disable IOMMU support

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Date:	Tue, 17 Feb 2015 14:08:03 +0100
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
Cc:	Kukjin Kim <kgene@...nel.org>, Olof Johansson <olof@...om.net>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Andreas Faerber <afaerber@...e.de>,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] ARM: exynos_defconfig: Disable IOMMU support

On wto, 2015-02-17 at 13:56 +0100, Javier Martinez Canillas wrote:
> Hello Krzysztof,
> 
> On 02/17/2015 01:20 PM, Krzysztof Kozlowski wrote:
> > On wto, 2015-02-17 at 12:38 +0100, Javier Martinez Canillas wrote:
> >> Enabling Exynos DRM IOMMU support for Exynos is currently broken and
> >> causes a BUG on exynos-iommu driver. This was not an issue since the
> >> options was disabled in exynos_defconfig but after commit 8dcc14f82f06
> >> ("drm/exynos: IOMMU support should not be selectable by user"), it is
> >> selected if EXYNOS_IOMMU is enabled which is in exynos_defconfig.
> >> 
> >> So a kernel built using exynos_defconfig after the mentioned commit
> >> fails to boot [0]. Disable IOMMU support in Exynos defconfig until
> >> things get sorted out.
> > 
> > On which board you got this error?
> > 
> 
> Sorry, I should had mention it in the commit message. I get that error
> with at least Exynos5800 Peach Pi, Exynos5420 Peach Pit and Exynos5250
> Snow Chromebooks with today's next (next-20150217).
> 
> The problem is that the Exynos IOMMU driver does not set a struct
> exynos_iommu_owner in dev.archdata.iommu but __exynos_sysmmu_enable()
> has a BUG_ON(!has_sysmmu(dev)).
> 
> Marek's series [1] solves this issue by filling sysmmu devices from DT
> but causes boot failures on the Exynos Chromebooks because the display
> is left enabled by the bootloader [2].
> 
> So I think that this option should be disabled until is known to not
> cause issues on any platform.

Sure, I am completely fine with that change. I just wanted to know the
hardware.

Anyway Marek already acked this I won't duplicate the effort :).

Best regards,
Krzysztof



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