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Date:   Mon, 14 Jan 2019 17:09:03 +0100
From:   Thierry Reding <treding@nvidia.com>
To:     Marek Szyprowski <m.szyprowski@samsung.com>
CC:     <iommu@lists.linux-foundation.org>, <linux-kernel@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        Christoph Hellwig <hch@lst.de>,
        Robin Murphy <robin.murphy@arm.com>,
        Russell King <rmk+kernel@armlinux.org.uk>,
        Ben Skeggs <bskeggs@redhat.com>,
        Tobias Jakobi <tjakobi@math.uni-bielefeld.de>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Subject: Re: [PATCH] Revert "ARM: dma-mapping: Set proper DMA ops in
 arm_iommu_detach_device()"
Message-ID: <20190114160902.GB9218@ulmo>
References: <CGME20190114132250eucas1p2abdf2f36bad3554e37dfbf40e539f594@eucas1p2.samsung.com>
 <20190114132240.12125-1-m.szyprowski@samsung.com>
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On Mon, Jan 14, 2019 at 02:22:40PM +0100, Marek Szyprowski wrote:
> This reverts commit 1874619a7df4b14b23b14877e705ae15325773e3.
>=20
> That patch broke IOMMU support for devices, which fails to probe for the
> first time and use deferred probe approach. When non-NULL dma_ops is set
> in arm_iommu_detach_device(), the given device later ignored by
> arch_setup_dma_ops() and stays with non-IOMMU dma_ops.
>=20
> Reported-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
> Fixes: 1874619a7df4 "ARM: dma-mapping: Set proper DMA ops in arm_iommu_de=
tach_device()"
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> ---
>  arch/arm/mm/dma-mapping.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)

Can you point out exactly what drivers break because of this change? We
need to find a solution that works for everyone. Reverting is only
marginally useful because somebody will just end up wanting to revert
the revert because a different driver is now broken.

Thierry

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