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From: Christoph Hellwig <hch@infradead.org>
To: Jonathan Marek <jonathan@marek.ca>
Cc: Christoph Hellwig <hch@infradead.org>,
	freedreno@lists.freedesktop.org, Rob Clark <robdclark@gmail.com>,
	Sean Paul <sean@poorly.run>, David Airlie <airlied@linux.ie>,
	Daniel Vetter <daniel@ffwll.ch>,
	"open list:DRM DRIVER FOR MSM ADRENO GPU" 
	<linux-arm-msm@vger.kernel.org>,
	"open list:DRM DRIVER FOR MSM ADRENO GPU" 
	<dri-devel@lists.freedesktop.org>,
	open list <linux-kernel@vger.kernel.org>,
	iommu@lists.linux-foundation.org, Joerg Roedel <joro@8bytes.org>,
	Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH 2/3] drm/msm: add DRM_MSM_GEM_SYNC_CACHE for non-coherent cache maintenance
Date: Wed, 7 Oct 2020 07:25:19 +0100	[thread overview]
Message-ID: <20201007062519.GA23519@infradead.org> (raw)
In-Reply-To: <148a1660-f0fc-7163-2240-6b94725342b5@marek.ca>

On Tue, Oct 06, 2020 at 09:19:32AM -0400, Jonathan Marek wrote:
> One example why drm/msm can't use DMA API is multiple page table support
> (that is landing in 5.10), which is something that definitely couldn't work
> with DMA API.
> 
> Another one is being able to choose the address for mappings, which AFAIK
> DMA API can't do (somewhat related to this: qcom hardware often has ranges
> of allowed addresses, which the dma_mask mechanism fails to represent, what
> I see is drivers using dma_mask as a "maximum address", and since addresses
> are allocated from the top it generally works)

That sounds like a good enough rason to use the IOMMU API.  I just
wanted to make sure this really makes sense.

WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@infradead.org>
To: Jonathan Marek <jonathan@marek.ca>
Cc: David Airlie <airlied@linux.ie>,
	freedreno@lists.freedesktop.org,
	open list <linux-kernel@vger.kernel.org>,
	"open list:DRM DRIVER FOR MSM ADRENO GPU"
	<dri-devel@lists.freedesktop.org>,
	Christoph Hellwig <hch@infradead.org>,
	iommu@lists.linux-foundation.org, Daniel Vetter <daniel@ffwll.ch>,
	"open list:DRM DRIVER FOR MSM ADRENO GPU"
	<linux-arm-msm@vger.kernel.org>, Sean Paul <sean@poorly.run>,
	Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH 2/3] drm/msm: add DRM_MSM_GEM_SYNC_CACHE for non-coherent cache maintenance
Date: Wed, 7 Oct 2020 07:25:19 +0100	[thread overview]
Message-ID: <20201007062519.GA23519@infradead.org> (raw)
In-Reply-To: <148a1660-f0fc-7163-2240-6b94725342b5@marek.ca>

On Tue, Oct 06, 2020 at 09:19:32AM -0400, Jonathan Marek wrote:
> One example why drm/msm can't use DMA API is multiple page table support
> (that is landing in 5.10), which is something that definitely couldn't work
> with DMA API.
> 
> Another one is being able to choose the address for mappings, which AFAIK
> DMA API can't do (somewhat related to this: qcom hardware often has ranges
> of allowed addresses, which the dma_mask mechanism fails to represent, what
> I see is drivers using dma_mask as a "maximum address", and since addresses
> are allocated from the top it generally works)

That sounds like a good enough rason to use the IOMMU API.  I just
wanted to make sure this really makes sense.
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

  reply	other threads:[~2020-10-07  6:25 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-01  0:27 [PATCH 0/3] drm/msm: support for host-cached BOs Jonathan Marek
2020-10-01  0:27 ` Jonathan Marek
2020-10-01  0:27 ` [PATCH 1/3] drm/msm: add MSM_BO_CACHED_COHERENT Jonathan Marek
2020-10-01  0:27   ` Jonathan Marek
2020-10-01 23:47   ` Jordan Crouse
2020-10-01 23:47     ` Jordan Crouse
2020-10-01  0:27 ` [PATCH 2/3] drm/msm: add DRM_MSM_GEM_SYNC_CACHE for non-coherent cache maintenance Jonathan Marek
2020-10-01  0:27   ` Jonathan Marek
2020-10-01 23:29   ` [Freedreno] " Jordan Crouse
2020-10-01 23:29     ` Jordan Crouse
2020-10-02  7:53   ` Christoph Hellwig
2020-10-02 12:46     ` Jonathan Marek
2020-10-02 12:46       ` Jonathan Marek
2020-10-05  8:29       ` Christoph Hellwig
2020-10-05 14:35         ` Jonathan Marek
2020-10-05 14:35           ` Jonathan Marek
2020-10-06  7:23           ` Christoph Hellwig
2020-10-06  7:23             ` Christoph Hellwig
2020-10-06 13:19             ` Jonathan Marek
2020-10-06 13:19               ` Jonathan Marek
2020-10-06 13:19               ` Jonathan Marek
2020-10-07  6:25               ` Christoph Hellwig [this message]
2020-10-07  6:25                 ` Christoph Hellwig
2020-10-13 13:42                 ` Robin Murphy
2020-10-13 13:42                   ` Robin Murphy
2020-10-13 13:42                   ` Robin Murphy
2020-10-13 16:11                   ` Rob Clark
2020-10-13 16:11                     ` Rob Clark
2020-10-13 16:11                     ` Rob Clark
2020-10-15  6:55                   ` Christoph Hellwig
2020-10-15  6:55                     ` Christoph Hellwig
2020-10-15 15:33                     ` Daniel Vetter
2020-10-15 15:33                       ` Daniel Vetter
2020-10-15 15:33                       ` Daniel Vetter
2020-10-15 15:43                       ` Christoph Hellwig
2020-10-15 15:43                         ` Christoph Hellwig
2020-10-23  6:48                         ` Christoph Hellwig
2020-10-23  6:48                           ` Christoph Hellwig
2020-10-08  8:27             ` Joerg Roedel
2020-10-08  8:27               ` Joerg Roedel
2020-10-08  8:27               ` Joerg Roedel
2020-10-01  0:27 ` [PATCH 3/3] drm/msm: bump up the uapi version Jonathan Marek
2020-10-01  0:27   ` Jonathan Marek

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