Re: [PATCH] arm64: dma-mapping: fix dma_to_phys API for IOMMU attached devices

Path	csiph.com!news.mixmin.net!aioe.org!gothmog.csi.it!bofh.it!news.nic.it!robomod
From	Sinan Kaya <okaya@codeaurora.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH] arm64: dma-mapping: fix dma_to_phys API for IOMMU attached devices
Date	Thu, 17 Mar 2016 17:10:04 +0100
Message-ID	<rdIEP-1aN-47@gated-at.bofh.it> (permalink)
References	<rdIv7-Qo-7@gated-at.bofh.it> <rdIv7-Qo-5@gated-at.bofh.it>
X-Original-To	Robin Murphy <robin.murphy@arm.com>, linux-arm-kernel@lists.infradead.org, timur@codeaurora.org, cov@codeaurora.org, nwatters@codeaurora.org
User-Agent	Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0
MIME-Version	1.0
Content-Type	text/plain; charset=windows-1252
Content-Transfer-Encoding	7bit
Sender	robomod@news.nic.it
List-ID	<linux-kernel.vger.kernel.org>
X-Mailing-List	linux-kernel@vger.kernel.org
Approved	robomod@news.nic.it
Lines	32
Organization	linux.* mail to news gateway
X-Original-Cc	Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will.deacon@arm.com>, Andrew Morton <akpm@linux-foundation.org>, Max Filippov <jcmvbkbc@gmail.com>, Joe Perches <joe@perches.com>, "Suthikulpanit, Suravee" <Suravee.Suthikulpanit@amd.com>, Arnd Bergmann <arnd@arndb.de>, Jisheng Zhang <jszhang@marvell.com>, Dean Nelson <dnelson@redhat.com>, "Suzuki K. Poulose" <suzuki.poulose@arm.com>, Marek Szyprowski <m.szyprowski@samsung.com>, linux-kernel@vger.kernel.org
X-Original-Date	Thu, 17 Mar 2016 12:07:26 -0400
X-Original-Message-ID	<56EAD63E.2010103@codeaurora.org>
X-Original-References	<1458229833-4886-1-git-send-email-okaya@codeaurora.org> <56EAD3E2.5070109@arm.com>
X-Original-Sender	linux-kernel-owner@vger.kernel.org
Xref	csiph.com linux.kernel:1359988

Show key headers only | View raw

On 3/17/2016 11:57 AM, Robin Murphy wrote:
>> This patch modifies dma_to_phys to call iommu_iova_to_phys to perform dma
>> to phys conversions for IOMMU attached devices where dma and physical
>> addresses often have distinct values.
> 
> What's this for? dma_to_phys() is only used by SWIOTLB, and that's mutually exclusive with IOMMU ops.

If it is SWIOTLB only, then it needs to disappear from common header file as 
it is doing the wrong thing when IOMMU is enabled for a device. 

I have some device driver (HIDMA) that used dma_to_phys during DMA self test.
I needed this patch to get it working properly. I removed the self test from
my code but I still don't feel right about this dma_to_phys API returning physical
addresses.

> 
> Also, what about phys_to_dma()?

Agreed, need to fix phys_to_dma too.

> 
> Robin.

Let me know which direction I should go. 

1. Fix phys_to_dma and keep dma_to_phys as in the patch.
2. Remove both of the API from header file, move it to where it is needed. Rename them as swio_phys_to_dma etc.

-- 
Sinan Kaya
Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project

Thread

Re: [PATCH] arm64: dma-mapping: fix dma_to_phys API for IOMMU  attached devices Robin Murphy <robin.murphy@arm.com> - 2016-03-17 17:00 +0100
  Re: [PATCH] arm64: dma-mapping: fix dma_to_phys API for IOMMU  attached devices Sinan Kaya <okaya@codeaurora.org> - 2016-03-17 17:10 +0100
    Re: [PATCH] arm64: dma-mapping: fix dma_to_phys API for IOMMU attached devices Arnd Bergmann <arnd@arndb.de> - 2016-03-17 17:20 +0100
      Re: [PATCH] arm64: dma-mapping: fix dma_to_phys API for IOMMU  attached devices Sinan Kaya <okaya@codeaurora.org> - 2016-03-17 17:40 +0100
        Re: [PATCH] arm64: dma-mapping: fix dma_to_phys API for IOMMU attached devices Arnd Bergmann <arnd@arndb.de> - 2016-03-17 18:10 +0100

csiph-web