[RFC PATCH 09/11] drivers: acpi: implement acpi_dma_configure
tn at semihalf.com
Mon May 16 08:15:34 PDT 2016
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 at 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
>> 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
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
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:
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
it be DMA_BIT_MASK(64). From that point on, we let to use memory which
SMMUv2 cannot work with.
Does lack of set_dma_mask is the only missing thing here?
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