From: will.deacon@arm•com (Will Deacon)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH URGENT] arm: dma-mapping: Set DMA IOMMU ops in arm_iommu_attach_device()
Date: Fri, 23 Jan 2015 17:04:55 +0000 [thread overview]
Message-ID: <20150123170455.GB13772@arm.com> (raw)
In-Reply-To: <2036088.T8IpDXjCxc@wuerfel>
On Fri, Jan 23, 2015 at 05:00:45PM +0000, Arnd Bergmann wrote:
> On Friday 23 January 2015 17:55:25 Laurent Pinchart wrote:
> >
> > On Friday 23 January 2015 16:27:24 Arnd Bergmann wrote:
> > > On Friday 23 January 2015 16:21:49 Laurent Pinchart wrote:
> > > > +/**
> > > > + * arm_iommu_detach_device
> > > > + * @dev: valid struct device pointer
> > > > + *
> > > > + * Detaches the provided device from a previously attached map.
> > > > + * This voids the dma operations (dma_map_ops pointer)
> > > > + */
> > > > +void arm_iommu_detach_device(struct device *dev)
> > > > +{
> > > > + __arm_iommu_detach_device(dev);
> > > > + set_dma_ops(dev, NULL);
> > > > +}
> > > >
> > > > EXPORT_SYMBOL_GPL(arm_iommu_detach_device);
> > >
> > > Would this introduce a regression in the case where the device is
> > > cache coherent and needs arm_coherent_dma_ops set?
> >
> > I think we need to handle that case (as well as the coherent IOMMU case in
> > arm_iommu_attach_device), but this patch only tries to restore the previous
> > behaviour to fix the bug detailed in the commit message. Would you prefer
> > fixing both issues in one go ?
> >
>
> No, I was specifically trying to find out whether the new behavior would
> be worse than what we had in 3.18. If it's a preexisting bug that nobody
> has run into, there is no hurry.
Agreed, I think Laurent's proposal here is the smallest thing that fixes
the issue without breaking the new of_xlate-based configuration.
Acked-by: Will Deacon <will.deacon@arm•com>
> It's quite likely that to date, all IOMMU users on ARM32 are not
> cache coherent.
Highbank has an ARM SMMU, but I don't see the iommu_coherent_ops getting
used, so your assertion is probably right.
Will
next prev parent reply other threads:[~2015-01-23 17:04 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-23 14:21 [PATCH URGENT] arm: dma-mapping: Set DMA IOMMU ops in arm_iommu_attach_device() Laurent Pinchart
2015-01-23 15:27 ` Arnd Bergmann
2015-01-23 15:55 ` Laurent Pinchart
2015-01-23 17:00 ` Arnd Bergmann
2015-01-23 17:04 ` Will Deacon [this message]
2015-01-26 0:34 ` Heiko Stübner
2015-01-26 10:42 ` Joerg Roedel
2015-01-28 0:25 ` Heiko Stübner
2015-01-29 18:57 ` Olof Johansson
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