linux-kernel - Re: [PATCH 03/22] iommu: Propagate error in add_iommu

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Date:	Mon, 29 Jun 2015 11:37:03 +0200
From:	Joerg Roedel <jroedel@...e.de>
To:	Heiko Stübner <heiko@...ech.de>
Cc:	Joerg Roedel <joro@...tes.org>, djkurtz@...omium.org,
	Tomasz Figa <tfiga@...omium.org>,
	iommu@...ts.linux-foundation.org,
	Will Deacon <will.deacon@....com>,
	Kukjin Kim <kgene@...nel.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Hiroshi Doyu <hdoyu@...dia.com>,
	Thierry Reding <thierry.reding@...il.com>,
	Alex Williamson <alex.williamson@...hat.com>,
	Robin Murphy <robin.murphy@....com>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Oded Gabbay <oded.gabbay@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/22] iommu: Propagate error in add_iommu_group

Hello Heiko,

On Mon, Jun 29, 2015 at 11:28:40AM +0200, Heiko Stübner wrote:
> The Rockchip iommu uses bus_set_ops to set its iommu-ops for the platform
> bus and currently returns -ENODEV if it encounters a platform_devices that
> does not have an iommu. As add_iommu_group ignored these returns
> till now this worked, but of course starts to fail now.
> 
> All two invocations of the add_device callback ignored (or still ignore) the
> return value so I've come with the following small patch to fix the breakage
> that now exists in the 4.2 tree.
> 
> There is probably a better solution possible in the longer term, likely
> similar to what Samsung does, but I'm not sure yet how this would work
> with our drm device that needs an iommu mapping without having an
> iommu (the iommus being attached to the crtc-components).

Yes, this issue was already reported from the Exynos side. I have a fix
which just ignores -ENODEV as the return value for now. This fixes
Exynos, and should fix Rockchip (and some other IOMMU drivers) too.


	Joerg

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