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Message-ID: <5739E68B.2080907@semihalf.com> Date: Mon, 16 May 2016 17:26:03 +0200 From: Tomasz Nowicki <tn@...ihalf.com> To: Robin Murphy <robin.murphy@....com>, Timur Tabi <timur@...eaurora.org>, Lorenzo Pieralisi <lorenzo.pieralisi@....com> Cc: "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, vikrams@...eaurora.org, Marc Zyngier <marc.zyngier@....com>, "Rafael J. Wysocki" <rjw@...ysocki.net>, lkml <linux-kernel@...r.kernel.org>, Will Deacon <will.deacon@....com>, Sinan Kaya <okaya@...eaurora.org>, linux-acpi@...r.kernel.org, iommu@...ts.linux-foundation.org, Hanjun Guo <hanjun.guo@...aro.org>, linux-pci@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>, Jon Masters <jcm@...hat.com> Subject: Re: [RFC PATCH 09/11] drivers: acpi: implement acpi_dma_configure On 16.05.2016 17:15, Tomasz Nowicki wrote: > On 18.04.2016 12:43, Robin Murphy wrote: >> On 15/04/16 19:29, Timur Tabi wrote: >>> On Thu, Apr 14, 2016 at 12:25 PM, Lorenzo Pieralisi >>> <lorenzo.pieralisi@....com> wrote: >>>> +void acpi_dma_configure(struct device *dev, enum dev_dma_attr attr) >>>> +{ >>>> + struct iommu_ops *iommu; >>>> + >>>> + iommu = iort_iommu_configure(dev); >>>> + >>>> + /* >>>> + * Assume dma valid range starts at 0 and covers the whole >>>> + * coherent_dma_mask. >>>> + */ >>>> + arch_setup_dma_ops(dev, 0, dev->coherent_dma_mask + 1, iommu, >>>> + attr == DEV_DMA_COHERENT); >>>> +} >>> >>> I have a network driver that is impacted by this code, so thank you >>> for posting this. (See >>> https://www.mail-archive.com/netdev@vger.kernel.org/msg106249.html). >>> >>> One one SOC, the driver needs to set the mask to 32 bits. On another >>> SOC, it needs to set it to 64 bits. On device tree, the driver will >>> use dma-ranges. >> >> That's the wrong way to look at it - the driver isn't _using_ >> dma-ranges, you're merely relying on the OF code setting the _default_ >> DMA mask differently based on the property. If your driver is in the >> minority of those which actually care about DMA masks, then it should be >> calling dma_set_mask_and_coherent() appropriately and not relying on the >> default. > > I don't see the clear strategy for setting DMA mask as well. > > Lets consider DT boot method example: > 1. SMMUv2 supports 48bit translation and 1:1 address map > dma-ranges = <0x0 0x0 0x0 0x0 0x00010000 0x0>; > and we are adding PCI device: > > pci_device_add -> DMA_BIT_MASK(32) by default > pci_dma_configure > of_dma_configure -> reads dma-ranges and calculates 48bit DMA mask, > but it picks minimum, we stay with DMA_BIT_MASK(32) > > now PCI dev turns out to be e1000e NIC: > e1000_probe > dma_set_mask_and_coherent -> tries to set DMA_BIT_MASK(64) > dma_set_mask -> there is no set_dma_mask ops for SMMUv2 so we let Sorry, there is no .set_dma_mask ops for ARM64 (not SMMUv2) Tomasz
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