From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marek Szyprowski Subject: Re: [PATCH 10/29] drivers: add DRIVER_HAS_OWN_IOMMU_MANAGER flag Date: Mon, 01 Sep 2014 14:07:34 +0200 Message-ID: <54046186.5030407@samsung.com> References: <1407235677-26324-1-git-send-email-m.szyprowski@samsung.com> <4621634.jlJLccozTJ@wuerfel> <54044EAC.6010701@samsung.com> <5493968.dbuSPSqts4@wuerfel> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-reply-to: <5493968.dbuSPSqts4@wuerfel> Sender: linux-samsung-soc-owner@vger.kernel.org To: Arnd Bergmann Cc: linux-arm-kernel@lists.infradead.org, Thierry Reding , Rob Herring , "linux-samsung-soc@vger.kernel.org" , Shaik Ameer Basha , Inki Dae , Greg Kroah-Hartman , Joerg Roedel , "Rafael J. Wysocki" , "linux-kernel@vger.kernel.org" , Tomasz Figa , "linaro-mm-sig@lists.linaro.org" , "iommu@lists.linux-foundation.org" , Kukjin Kim , Laurent Pinchart , Sylwester Nawrocki , Olof Johansson , Kyungmin Park , Cho KyongHo List-Id: iommu@lists.linux-foundation.org Hello, On 2014-09-01 13:56, Arnd Bergmann wrote: > On Monday 01 September 2014 12:47:08 Marek Szyprowski wrote: >>> Who do you think needs to set this flag, and who needs to read it? >> In the proposed solution Exynos IOMMU driver creates a separate IO >> address space >> for every client device in a system and binds it to the default >> dma-mapping space >> for the given device. When drivers are doing its own management of IO >> address >> space, instead of relying on what is available by default with dma-mapping >> interface, this will require releasing of the previously created default >> structures and resources. So this flag is set by the driver doing its own >> management of io address space. The flags is then checked by Exynos >> IOMMU driver >> to avoid creating the default dma-mapping address space for devices >> which driver >> does its own management. > I don't completely understand it yet. I would assume the device > to be added to the default domain at device creation time > (of_platform_populate), way before we know which device driver > is going to be used. How can this prevent the iommu driver > from doing the association with the domain? of_platform_populate() is too early to do the association, because that time the exynos iommu driver is even not yet probed. The association with default dma-mapping domain is done in IOMMU_GROUP_NOTIFY_BIND_DRIVER notifier, just before binding the driver to the given device. This way iommu driver can check dev->driver->flags and skip creating default dma-mapping domain if driver announces that it wants to handle it by itself. Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland From mboxrd@z Thu Jan 1 00:00:00 1970 From: m.szyprowski@samsung.com (Marek Szyprowski) Date: Mon, 01 Sep 2014 14:07:34 +0200 Subject: [PATCH 10/29] drivers: add DRIVER_HAS_OWN_IOMMU_MANAGER flag In-Reply-To: <5493968.dbuSPSqts4@wuerfel> References: <1407235677-26324-1-git-send-email-m.szyprowski@samsung.com> <4621634.jlJLccozTJ@wuerfel> <54044EAC.6010701@samsung.com> <5493968.dbuSPSqts4@wuerfel> Message-ID: <54046186.5030407@samsung.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hello, On 2014-09-01 13:56, Arnd Bergmann wrote: > On Monday 01 September 2014 12:47:08 Marek Szyprowski wrote: >>> Who do you think needs to set this flag, and who needs to read it? >> In the proposed solution Exynos IOMMU driver creates a separate IO >> address space >> for every client device in a system and binds it to the default >> dma-mapping space >> for the given device. When drivers are doing its own management of IO >> address >> space, instead of relying on what is available by default with dma-mapping >> interface, this will require releasing of the previously created default >> structures and resources. So this flag is set by the driver doing its own >> management of io address space. The flags is then checked by Exynos >> IOMMU driver >> to avoid creating the default dma-mapping address space for devices >> which driver >> does its own management. > I don't completely understand it yet. I would assume the device > to be added to the default domain at device creation time > (of_platform_populate), way before we know which device driver > is going to be used. How can this prevent the iommu driver > from doing the association with the domain? of_platform_populate() is too early to do the association, because that time the exynos iommu driver is even not yet probed. The association with default dma-mapping domain is done in IOMMU_GROUP_NOTIFY_BIND_DRIVER notifier, just before binding the driver to the given device. This way iommu driver can check dev->driver->flags and skip creating default dma-mapping domain if driver announces that it wants to handle it by itself. Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland