From: Robin Murphy <robin.murphy@arm.com>
To: Timur Tabi <timur@codeaurora.org>,
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: "linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
vikrams@codeaurora.org, Marc Zyngier <marc.zyngier@arm.com>,
Tomasz Nowicki <tn@semihalf.com>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
lkml <linux-kernel@vger.kernel.org>,
Will Deacon <will.deacon@arm.com>,
Sinan Kaya <okaya@codeaurora.org>,
linux-acpi@vger.kernel.org, iommu@lists.linux-foundation.org,
Hanjun Guo <hanjun.guo@linaro.org>,
linux-pci@vger.kernel.org, Bjorn Helgaas <bhelgaas@google.com>,
Jon Masters <jcm@redhat.com>
Subject: Re: [RFC PATCH 09/11] drivers: acpi: implement acpi_dma_configure
Date: Mon, 18 Apr 2016 11:43:38 +0100 [thread overview]
Message-ID: <5714BA5A.2040008@arm.com> (raw)
In-Reply-To: <CAOZdJXXtZq6uyE+5sseX7M_6Kq8wFG+37qd5TNSusKj=0gd8zA@mail.gmail.com>
On 15/04/16 19:29, Timur Tabi wrote:
> On Thu, Apr 14, 2016 at 12:25 PM, Lorenzo Pieralisi
> <lorenzo.pieralisi@arm.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.
> In your patches, where is coherent_dma_mask initialized? I found this
> code in add_smmu_platform_device(), but I think this is setting the
> mask for the IOMMU driver, not the individual devices.
Yes, that's for the SMMU itself as a device (i.e. the page table walker)
- as a handy example of "drivers which actually care about DMA masks",
it specifically needs to avoid a too-small DMA mask because
bounce-buffering the page tables tends to make things go horribly wrong.
Robin.
> Either way, I
> don't understand where the correct value is going to be overridden.
>
> + /*
> + * Set default dma mask value for the table walker,
> + * to be overridden on probing with correct value.
> + */
> + *pdev->dev.dma_mask = DMA_BIT_MASK(32);
> + pdev->dev.coherent_dma_mask = *pdev->dev.dma_mask;
>
next prev parent reply other threads:[~2016-04-18 10:43 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-14 17:25 [RFC PATCH 00/11] ACPI IORT ARM SMMU support Lorenzo Pieralisi
2016-04-14 17:25 ` [RFC PATCH 01/11] drivers: acpi: iort: fix struct pci_dev compiler warnings Lorenzo Pieralisi
2016-04-14 17:25 ` [RFC PATCH 02/11] drivers: acpi: iort: add support for IOMMU registration Lorenzo Pieralisi
2016-04-14 17:25 ` [RFC PATCH 03/11] drivers: iommu: add FWNODE_IOMMU fwnode type Lorenzo Pieralisi
2016-04-14 17:25 ` [RFC PATCH 04/11] drivers: acpi: iort: introduce linker section for IORT entries probing Lorenzo Pieralisi
2016-04-14 17:25 ` [RFC PATCH 05/11] drivers: iommu: arm-smmu: split probe functions into DT/generic portions Lorenzo Pieralisi
2016-04-14 17:25 ` [RFC PATCH 06/11] drivers: iommu: make of_xlate() interface DT agnostic Lorenzo Pieralisi
2016-04-19 8:28 ` Marek Szyprowski
2016-04-19 11:30 ` Lorenzo Pieralisi
2016-04-20 7:14 ` Marek Szyprowski
2016-04-14 17:25 ` [RFC PATCH 07/11] drivers: iommu: arm-smmu: allow ACPI based streamid translation Lorenzo Pieralisi
2016-04-14 17:25 ` [RFC PATCH 08/11] drivers: acpi: iort: enhance mapping API Lorenzo Pieralisi
2016-04-14 17:25 ` [RFC PATCH 09/11] drivers: acpi: implement acpi_dma_configure Lorenzo Pieralisi
2016-04-15 16:14 ` Bjorn Helgaas
2016-04-15 16:31 ` Robin Murphy
2016-04-15 18:29 ` Timur Tabi
2016-04-18 10:30 ` Lorenzo Pieralisi
2016-04-18 10:43 ` Robin Murphy [this message]
2016-05-16 15:15 ` Tomasz Nowicki
2016-05-16 15:26 ` Tomasz Nowicki
2016-04-21 22:45 ` Andy Shevchenko
2016-04-22 10:57 ` Lorenzo Pieralisi
2016-05-17 8:07 ` Tomasz Nowicki
2016-05-17 12:32 ` Tomasz Nowicki
2016-04-14 17:25 ` [RFC PATCH 10/11] drivers: iommu: arm-smmu: implement ACPI probing Lorenzo Pieralisi
2016-04-14 17:25 ` [RFC PATCH 11/11] drivers: irqchip: make struct irq_fwspec generic Lorenzo Pieralisi
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