linux-kernel - Re: [PATCH] ARM: dma-mapping: Clear DMA ops on teardown

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Date:   Mon, 21 Jan 2019 16:34:40 +0100
From:   Thierry Reding <treding@...dia.com>
To:     Robin Murphy <robin.murphy@....com>
CC:     <iommu@...ts.linux-foundation.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <m.szyprowski@...sung.com>,
        <hch@....de>, <rmk+kernel@...linux.org.uk>, <bskeggs@...hat.com>,
        <tjakobi@...h.uni-bielefeld.de>, <b.zolnierkie@...sung.com>
Subject: Re: [PATCH] ARM: dma-mapping: Clear DMA ops on teardown

On Mon, Jan 21, 2019 at 02:52:16PM +0000, Robin Murphy wrote:
> Installing the appropriate non-IOMMU DMA ops in arm_iommu_detch_device()
> serves the case where IOMMU-aware drivers choose to control their own
> mapping but still make DMA API calls, however it also affects the case
> when the arch code itself tears down the mapping upon driver unbinding,
> where the ops now get left in place and can inhibit arch_setup_dma_ops()
> on subsequent re-probe attempts.
> 
> Fix the latter case by making sure that arch_teardown_dma_ops() cleans
> up whenever the ops were automatically installed by its counterpart.
> 
> Reported-by: Tobias Jakobi <tjakobi@...h.uni-bielefeld.de>
> Reported-by: Marek Szyprowski <m.szyprowski@...sung.com>
> Fixes: 1874619a7df4 "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()"
> Tested-by: Tobias Jakobi <tjakobi@...h.uni-bielefeld.de>
> Signed-off-by: Robin Murphy <robin.murphy@....com>
> ---
> 
> Sorry for the delay - there was a giant email infrastructure cock-up just
> at the point I wanted to go back through my archive and double-check the
> discussion around the original commit...
> 
> Robin.
> 
>  arch/arm/mm/dma-mapping.c | 2 ++
>  1 file changed, 2 insertions(+)

I had also tested your draft on Tegra last week and this looks
identical, so:

Tested-by: Thierry Reding <treding@...dia.com>

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