[RFC 0/5] ARM: dma-mapping: New dma_map_ops to control IOVA more precisely

[Stephen Warren]

On 09/19/2012 07:44 PM, Krishna Reddy wrote:
>> When a device driver would only use the IOMMU-API and needs small DMA-
>> able areas it has to re-implement something like the DMA-API (basically an
>> address allocator) for that. So I don't see a reason why both can't be used in a
>> device driver.
> 
> On Tegra, the following use cases need specific IOVA mapping.
> 1. Few MMIO blocks need IOVA=PA mapping setup.

In that case, why would we enable the IOMMU for that one device; IOMMU
disabled means VA==PA, right? Perhaps isolation of the device so it can
only access certain PA ranges for security?