From mboxrd@z Thu Jan 1 00:00:00 1970 From: Will Deacon Subject: Re: [RFC PATCH v3 5/7] dma-mapping: detect and configure IOMMU in of_dma_configure Date: Mon, 22 Sep 2014 18:50:27 +0100 Message-ID: <20140922175027.GK7936@arm.com> References: <1410539695-29128-1-git-send-email-will.deacon@arm.com> <1410539695-29128-6-git-send-email-will.deacon@arm.com> <4252161.sBJZLIS2WH@avalon> <20140922092909.GJ1470@ulmo> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20140922092909.GJ1470@ulmo> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Thierry Reding Cc: "jroedel-l3A5Bk7waGM@public.gmane.org" , "arnd-r2nGTMty4D4@public.gmane.org" , "iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org" , Laurent Pinchart , "Varun.Sethi-KZfg59tc24xl57MIdRCFDg@public.gmane.org" , "dwmw2-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org" , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" List-Id: iommu@lists.linux-foundation.org On Mon, Sep 22, 2014 at 10:29:10AM +0100, Thierry Reding wrote: > On Thu, Sep 18, 2014 at 02:17:33PM +0300, Laurent Pinchart wrote: > > On Friday 12 September 2014 17:34:53 Will Deacon wrote: > > > This patch extends of_dma_configure so that it sets up the IOMMU for a > > > device, as well as the coherent/non-coherent DMA mapping ops. > > > > > > Signed-off-by: Will Deacon > > > --- > > > arch/arm/include/asm/dma-mapping.h | 4 +++- > > > drivers/of/platform.c | 24 +++++++++++++++++------- > > > include/linux/dma-mapping.h | 8 +++++++- > > > 3 files changed, 27 insertions(+), 9 deletions(-) > > > > > > diff --git a/arch/arm/include/asm/dma-mapping.h > > > b/arch/arm/include/asm/dma-mapping.h index 7e9ac4f604c3..a8bb0c494bb3 > > > 100644 > > > --- a/arch/arm/include/asm/dma-mapping.h > > > +++ b/arch/arm/include/asm/dma-mapping.h > > > @@ -121,7 +121,9 @@ static inline unsigned long dma_max_pfn(struct device > > > *dev) } > > > #define dma_max_pfn(dev) dma_max_pfn(dev) > > > > > > -static inline void arch_setup_dma_ops(struct device *dev, bool coherent) > > > +static inline void arch_setup_dma_ops(struct device *dev, u64 dma_base, > > > + u64 size, struct iommu_dma_mapping *iommu, > > > + bool coherent) > > > { > > > if (coherent) > > > set_dma_ops(dev, &arm_coherent_dma_ops); > > > diff --git a/drivers/of/platform.c b/drivers/of/platform.c > > > index 946dd7ae0394..95ebd38db545 100644 > > > --- a/drivers/of/platform.c > > > +++ b/drivers/of/platform.c > > > @@ -19,6 +19,7 @@ > > > #include > > > #include > > > #include > > > +#include > > > #include > > > #include > > > #include > > > @@ -166,6 +167,7 @@ static void of_dma_configure(struct platform_device > > > *pdev) int ret; > > > bool coherent; > > > unsigned long offset; > > > + struct iommu_dma_mapping *iommu; > > > struct device *dev = &pdev->dev; > > > > > > /* > > > @@ -195,7 +197,19 @@ static void of_dma_configure(struct platform_device > > > *pdev) dev_dbg(dev, "device is%sdma coherent\n", > > > coherent ? " " : " not "); > > > > > > - arch_setup_dma_ops(dev, coherent); > > > + iommu = of_iommu_configure(dev); > > > + dev_dbg(dev, "device is%sbehind an iommu\n", > > > + iommu ? " " : " not "); > > > + > > > + arch_setup_dma_ops(dev, dma_addr, size, iommu, coherent); > > > + > > > + if (iommu) > > > + kref_put(&iommu->kref, of_iommu_deconfigure); > > > > What's the expected life cycle of the iommu_dma_mapping structure ? It gets > > created by of_iommu_configure() and the initial reference gets dropped here. I > > suppose you expect arch code to need to keep a reference to the structure, but > > your implementation in patch 7/7 doesn't. As far as I can see, you don't even > > use the contents of the structure in the ARM arch_setup_dma_ops() > > implementation. Do you expect that to change later, or other architectures to > > need it ? > > > > By the way, now that I think about it, I find struct iommu_dma_mapping and > > struct dma_iommu_mapping very confusing. > > Agreed. I wonder how useful it is to know the set of IOMMU instances > that each device can master through. Wouldn't it be more useful to keep > a list of master interfaces for each device? The set of IOMMU instances > can trivially be derived from that. I'm struggling to think how that would look. What do you mean by `master interfaces' in terms of the code we have in Linux? At the end of the day, the list of IOMMU instances (i.e. iommu_dma_mapping) exists because you and Laurent have use-cases involving devices mastering through multiple IOMMUs. If it doesn't work for you, it might be best for you to send me the patch ;) Will