linux-kernel - Re: [PATCH 00/29] Exynos SYSMMU (IOMMU) integration with DT and DMA-mapping subsystem

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Date:	Tue, 19 Aug 2014 14:30:59 +0200
From:	Andreas Färber <afaerber@...e.de>
To:	Marek Szyprowski <m.szyprowski@...sung.com>,
	Inki Dae <inki.dae@...sung.com>
CC:	Joerg Roedel <joro@...tes.org>, iommu@...ts.linux-foundation.org,
	linux-samsung-soc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linaro-mm-sig@...ts.linaro.org, Arnd Bergmann <arnd@...db.de>,
	Shaik Ameer Basha <shaik.ameer@...sung.com>,
	Cho KyongHo <pullip.cho@...sung.com>,
	Thierry Reding <treding@...dia.com>,
	Olof Johansson <olof@...om.net>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Rob Herring <robh@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Sylwester Nawrocki <s.nawrocki@...sung.com>,
	Tomasz Figa <tomasz.figa@...il.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Ajay Kumar <ajaykumar.rs@...sung.com>
Subject: Re: [PATCH 00/29] Exynos SYSMMU (IOMMU) integration with DT and DMA-mapping
 subsystem

Hi,

Am 19.08.2014 14:01, schrieb Marek Szyprowski:
> On 2014-08-19 13:39, Andreas Färber wrote:
>> I'm working on 5250 based Spring Chromebook and noticed that v3.17-rc1
>> got some more iommu support. With the new CONFIG_DRM_EXYNOS_IOMMU=y my
>> machine stops booting. So I'm wondering, is any of this a fix for 3.17,
>> or is all of this "unrelated" -next material?
> 
> This is probably a side effect of patch
> 3170447c1f264d51b8d1f3898bf2588588a64fdc
> ("iommu/exynos: Select ARM_DMA_USE_IOMMU"). It added selection of
> ARM_DMA_USE_IOMMU
> symbol, on which IOMMU support in Exynos DRM subsystem depends. However
> selecting
> this symbol is all that this patch does, without providing any code code
> which
> implements real support for ARM DMA IOMMU integration, which is needed
> by Exynos
> DRM driver. Please disable CONFIG_DRM_EXYNOS_IOMMU in kernel .config and
> your
> system should be bootable again.

Yes, that's what my report implied. :)

I'm bringing this up for -rc2 though: It sounds as if that option should
remain unavailable until the required code is in? Thanks.

>> Also, are you or someone
>> working on the respective DT changes for Exynos5?
> 
> I can prepare DT changes for Exynos5 as well, but first I wanted to
> clarify if
> everyone involved in generic IOMMU bindings and Exynos IOMMU driver
> agrees on my
> proposal.

Sure. I'm updating my old spring-bridge.v6 branch [1] to 3.17-rc1 [2],
which involves three drm bridge patches rebased onto the new drm panel
prepare/unprepare infrastructure plus two LVDS DT patches in addition to
the IOMMU patches. That old branch included DT changes for 5250 in "ARM:
dts: add System MMU nodes of Exynos SoCs", but that'll probably need
updating for the new bindings.

Regards,
Andreas

[1] https://github.com/afaerber/linux/commits/spring-bridge.v6
[2] https://github.com/afaerber/linux/commits/spring-next

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