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

From: [email-masked] (Andreas Färber)
Date: Tue, 19 Aug 2014 14:30:59 +0200

Hi,

Am 19.08.2014 14:01, schrieb Marek Szyprowski:
> On 2014-08-19 13:39, Andreas F?rber 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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