From: Christoph Hellwig <hch@lst.de> To: Jonathan Marek <jonathan@marek.ca> Cc: freedreno@lists.freedesktop.org, hch@lst.de, Marek Szyprowski <m.szyprowski@samsung.com>, Robin Murphy <robin.murphy@arm.com>, "open list:DMA MAPPING HELPERS" <iommu@lists.linux-foundation.org>, open list <linux-kernel@vger.kernel.org> Subject: Re: [RESEND PATCH v2 2/5] dma-direct: add dma_direct_bypass() to force direct ops Date: Sat, 14 Nov 2020 17:21:09 +0100 [thread overview] Message-ID: <20201114162109.GA24411@lst.de> (raw) In-Reply-To: <20201114151717.5369-3-jonathan@marek.ca> On Sat, Nov 14, 2020 at 10:17:10AM -0500, Jonathan Marek wrote: > Add a function to force direct ops and disable swiotlb for a deivce. s/deivce/device/ > +#if IS_ENABLED(CONFIG_DMA_OPS_BYPASS) && !IS_ENABLED(CONFIG_ARCH_HAS_FORCE_DMA_UNENCRYPTED) overly long line. > +#if IS_ENABLED(CONFIG_DMA_OPS_BYPASS) && !IS_ENABLED(CONFIG_ARCH_HAS_FORCE_DMA_UNENCRYPTED) Again. > +int dma_direct_bypass(struct device *dev) > +{ > + int ret; > + > + ret = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64)); > + if (ret) > + return ret; > + > + dev->bus_dma_limit = DMA_BIT_MASK(64); > + dev->dma_ops_bypass = true; > + return 0; > +} > +EXPORT_SYMBOL_GPL(dma_direct_bypass); But more importantly ARCH_HAS_FORCE_DMA_UNENCRYPTED is just a compile time flag. With this you disable the functionality for all the usual x86, s390 and powerpc configs, while only a tiny number of systems for bounce buffering. But I think you can just trivialy check force_dma_unencrypted instead. We do not need an extra Kconfig symbol symbol for this trivial helper. Also the helper is misnamed and misplaced. The semantics have nothing to do with dma-direct, the fact that is uses the ops bypass is an implementation detail. It really fits into the iommu code, as it allows the driver to use the IOMMU API for IOVA management, while using the DMA API for cache management. So it should be named to reflect that, and also grow a kerneldoc comment explaining how it will be used.
WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de> To: Jonathan Marek <jonathan@marek.ca> Cc: freedreno@lists.freedesktop.org, open list <linux-kernel@vger.kernel.org>, "open list:DMA MAPPING HELPERS" <iommu@lists.linux-foundation.org>, Robin Murphy <robin.murphy@arm.com>, hch@lst.de Subject: Re: [RESEND PATCH v2 2/5] dma-direct: add dma_direct_bypass() to force direct ops Date: Sat, 14 Nov 2020 17:21:09 +0100 [thread overview] Message-ID: <20201114162109.GA24411@lst.de> (raw) In-Reply-To: <20201114151717.5369-3-jonathan@marek.ca> On Sat, Nov 14, 2020 at 10:17:10AM -0500, Jonathan Marek wrote: > Add a function to force direct ops and disable swiotlb for a deivce. s/deivce/device/ > +#if IS_ENABLED(CONFIG_DMA_OPS_BYPASS) && !IS_ENABLED(CONFIG_ARCH_HAS_FORCE_DMA_UNENCRYPTED) overly long line. > +#if IS_ENABLED(CONFIG_DMA_OPS_BYPASS) && !IS_ENABLED(CONFIG_ARCH_HAS_FORCE_DMA_UNENCRYPTED) Again. > +int dma_direct_bypass(struct device *dev) > +{ > + int ret; > + > + ret = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64)); > + if (ret) > + return ret; > + > + dev->bus_dma_limit = DMA_BIT_MASK(64); > + dev->dma_ops_bypass = true; > + return 0; > +} > +EXPORT_SYMBOL_GPL(dma_direct_bypass); But more importantly ARCH_HAS_FORCE_DMA_UNENCRYPTED is just a compile time flag. With this you disable the functionality for all the usual x86, s390 and powerpc configs, while only a tiny number of systems for bounce buffering. But I think you can just trivialy check force_dma_unencrypted instead. We do not need an extra Kconfig symbol symbol for this trivial helper. Also the helper is misnamed and misplaced. The semantics have nothing to do with dma-direct, the fact that is uses the ops bypass is an implementation detail. It really fits into the iommu code, as it allows the driver to use the IOMMU API for IOVA management, while using the DMA API for cache management. So it should be named to reflect that, and also grow a kerneldoc comment explaining how it will be used. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
next prev parent reply other threads:[~2020-11-14 16:21 UTC|newest] Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-11-14 15:17 [RESEND PATCH v2 0/5] drm/msm: support for host-cached BOs Jonathan Marek 2020-11-14 15:17 ` Jonathan Marek 2020-11-14 15:17 ` Jonathan Marek 2020-11-14 15:17 ` [RESEND PATCH v2 1/5] drm/msm: add MSM_BO_CACHED_COHERENT Jonathan Marek 2020-11-14 15:17 ` Jonathan Marek 2020-11-14 15:17 ` [RESEND PATCH v2 2/5] dma-direct: add dma_direct_bypass() to force direct ops Jonathan Marek 2020-11-14 15:17 ` Jonathan Marek 2020-11-14 16:21 ` Christoph Hellwig [this message] 2020-11-14 16:21 ` Christoph Hellwig 2020-11-14 15:17 ` [RESEND PATCH v2 3/5] drm/msm: call dma_direct_bypass() Jonathan Marek 2020-11-14 15:17 ` Jonathan Marek 2020-11-14 16:21 ` Christoph Hellwig 2020-11-14 15:17 ` [RESEND PATCH v2 4/5] drm/msm: add DRM_MSM_GEM_SYNC_CACHE for non-coherent cache maintenance Jonathan Marek 2020-11-14 15:17 ` Jonathan Marek 2020-11-14 16:24 ` Christoph Hellwig 2020-11-14 18:46 ` Rob Clark 2020-11-14 18:46 ` Rob Clark 2020-11-14 18:54 ` Jonathan Marek 2020-11-14 18:54 ` Jonathan Marek 2020-11-14 19:39 ` Rob Clark 2020-11-14 19:39 ` Rob Clark 2020-11-14 20:07 ` Jonathan Marek 2020-11-14 20:07 ` Jonathan Marek 2020-11-14 20:48 ` Rob Clark 2020-11-14 20:48 ` Rob Clark 2020-11-16 17:33 ` Christoph Hellwig 2020-11-16 17:50 ` Rob Clark 2020-11-16 17:50 ` Rob Clark 2020-11-16 17:52 ` Jonathan Marek 2020-11-16 17:52 ` Jonathan Marek 2020-11-29 18:51 ` Rob Clark 2020-11-29 18:51 ` Rob Clark 2020-11-16 17:27 ` [Freedreno] " Jordan Crouse 2020-11-16 17:27 ` Jordan Crouse 2020-11-16 17:25 ` Jordan Crouse 2020-11-16 17:25 ` Jordan Crouse 2020-11-14 15:17 ` [RESEND PATCH v2 5/5] drm/msm: bump up the uapi version Jonathan Marek 2020-11-14 15:17 ` Jonathan Marek
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