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From: Thierry Reding <thierry.reding@gmail.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: nouveau@lists.freedesktop.org,
	Russell King <linux@armlinux.org.uk>,
	dri-devel@lists.freedesktop.org,
	iommu@lists.linux-foundation.org, linux-tegra@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 2/5] dma-mapping: Introduce dma_iommu_detach_device() API
Date: Mon, 30 Apr 2018 13:02:31 +0200	[thread overview]
Message-ID: <20180430110231.GF2476@ulmo> (raw)
In-Reply-To: <20180426121136.GD11985@ulmo>


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On Thu, Apr 26, 2018 at 02:11:36PM +0200, Thierry Reding wrote:
> On Wed, Apr 25, 2018 at 08:19:34AM -0700, Christoph Hellwig wrote:
> > On Wed, Apr 25, 2018 at 12:10:48PM +0200, Thierry Reding wrote:
> > > From: Thierry Reding <treding@nvidia.com>
> > > 
> > > The dma_iommu_detach_device() API can be used by drivers to forcibly
> > > detach a device from an IOMMU that architecture code might have attached
> > > to. This is useful for drivers that need explicit control over the IOMMU
> > > using the IOMMU API directly.
> > 
> > Given that no one else implements it making it a generic API seems
> > rather confusing.  For now I'd rename it to
> > arm_dma_iommu_detach_device() and only implement it in arm.
> 
> That'd be suboptimal because this code is used on both 32-bit and 64-bit
> ARM. If we make the function 32-bit ARM specific then the driver code
> would need to use an #ifdef to make sure compilation doesn't break on
> 64-bit ARM.

Do you still want me to make this ARM specific? While I haven't
encountered this issue on 64-bit ARM yet, I think it would happen there
as well, under the right circumstances. I could take a shot at
implementing the equivalent there (which means essentially implementing
it for drivers/iommu/dma-iommu.c and calling that from 64-bit ARM code).

Thierry

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WARNING: multiple messages have this Message-ID (diff)
From: thierry.reding@gmail.com (Thierry Reding)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2 2/5] dma-mapping: Introduce dma_iommu_detach_device() API
Date: Mon, 30 Apr 2018 13:02:31 +0200	[thread overview]
Message-ID: <20180430110231.GF2476@ulmo> (raw)
In-Reply-To: <20180426121136.GD11985@ulmo>

On Thu, Apr 26, 2018 at 02:11:36PM +0200, Thierry Reding wrote:
> On Wed, Apr 25, 2018 at 08:19:34AM -0700, Christoph Hellwig wrote:
> > On Wed, Apr 25, 2018 at 12:10:48PM +0200, Thierry Reding wrote:
> > > From: Thierry Reding <treding@nvidia.com>
> > > 
> > > The dma_iommu_detach_device() API can be used by drivers to forcibly
> > > detach a device from an IOMMU that architecture code might have attached
> > > to. This is useful for drivers that need explicit control over the IOMMU
> > > using the IOMMU API directly.
> > 
> > Given that no one else implements it making it a generic API seems
> > rather confusing.  For now I'd rename it to
> > arm_dma_iommu_detach_device() and only implement it in arm.
> 
> That'd be suboptimal because this code is used on both 32-bit and 64-bit
> ARM. If we make the function 32-bit ARM specific then the driver code
> would need to use an #ifdef to make sure compilation doesn't break on
> 64-bit ARM.

Do you still want me to make this ARM specific? While I haven't
encountered this issue on 64-bit ARM yet, I think it would happen there
as well, under the right circumstances. I could take a shot at
implementing the equivalent there (which means essentially implementing
it for drivers/iommu/dma-iommu.c and calling that from 64-bit ARM code).

Thierry
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  reply	other threads:[~2018-04-30 11:02 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-25 10:10 [PATCH v2 1/5] drm/nouveau: tegra: Detach from ARM DMA/IOMMU mapping Thierry Reding
2018-04-25 10:10 ` Thierry Reding
     [not found] ` <20180425101051.15349-1-thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2018-04-25 10:10   ` [PATCH v2 2/5] dma-mapping: Introduce dma_iommu_detach_device() API Thierry Reding
2018-04-25 10:10     ` Thierry Reding
     [not found]     ` <20180425101051.15349-2-thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2018-04-25 15:19       ` Christoph Hellwig
2018-04-25 15:19         ` Christoph Hellwig
     [not found]         ` <20180425151934.GC16075-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2018-04-26 12:11           ` Thierry Reding
2018-04-26 12:11             ` Thierry Reding
2018-04-30 11:02             ` Thierry Reding [this message]
2018-04-30 11:02               ` Thierry Reding
2018-04-30 11:41               ` Robin Murphy
2018-04-30 11:41                 ` Robin Murphy
     [not found]                 ` <e549979d-9f53-a329-da1a-ed5139958762-5wv7dgnIgG8@public.gmane.org>
2018-04-30 12:12                   ` Thierry Reding
2018-04-30 12:12                     ` Thierry Reding
2018-04-30 12:49                     ` Robin Murphy
2018-04-30 12:49                       ` Robin Murphy
2018-04-25 10:10   ` [PATCH v2 3/5] ARM: dma-mapping: Implement arch_iommu_detach_device() Thierry Reding
2018-04-25 10:10     ` Thierry Reding
     [not found]     ` <20180425101051.15349-3-thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2018-04-25 15:20       ` Christoph Hellwig
2018-04-25 15:20         ` Christoph Hellwig
     [not found]         ` <20180425152049.GD16075-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2018-04-26 12:14           ` Thierry Reding
2018-04-26 12:14             ` Thierry Reding
2018-04-25 10:10   ` [PATCH v2 4/5] drm/nouveau: tegra: Use dma_iommu_detach_device() Thierry Reding
2018-04-25 10:10     ` Thierry Reding
2018-04-25 10:10   ` [PATCH v2 5/5] ARM: Unconditionally enable ARM_DMA_USE_IOMMU Thierry Reding
2018-04-25 10:10     ` Thierry Reding
     [not found]     ` <20180425101051.15349-5-thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2018-04-25 10:25       ` Russell King - ARM Linux
2018-04-25 10:25         ` Russell King - ARM Linux
2018-04-25 15:17         ` Christoph Hellwig
2018-04-25 15:17           ` Christoph Hellwig
2018-04-25 15:18   ` [PATCH v2 1/5] drm/nouveau: tegra: Detach from ARM DMA/IOMMU mapping Christoph Hellwig
2018-04-25 15:18     ` Christoph Hellwig
     [not found]     ` <20180425151815.GB16075-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2018-04-26 12:09       ` Thierry Reding
2018-04-26 12:09         ` Thierry Reding
2018-04-25 15:28 ` Jordan Crouse
2018-04-25 15:28   ` Jordan Crouse
     [not found]   ` <20180425152849.GA2447-9PYrDHPZ2Orvke4nUoYGnHL1okKdlPRT@public.gmane.org>
2018-04-26 12:41     ` Thierry Reding
2018-04-26 12:41       ` Thierry Reding
2018-04-26 12:59       ` Mikko Perttunen
2018-04-26 12:59         ` Mikko Perttunen
     [not found]         ` <fd6e0d90-7614-296b-2927-7b2745e8fbde-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
2018-04-26 13:14           ` Thierry Reding
2018-04-26 13:14             ` Thierry Reding

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