Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [PATCH v2 4/5] iommu: Use dma_addr_t for IOVA arguments | Date | Wed, 07 May 2014 09:58:58 +0200 |
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On Tuesday 06 May 2014 16:48:40 Bjorn Helgaas wrote: > Convert the "iova" arguments of iommu_map(), iommu_unmap(), etc., from > "unsigned long" to dma_addr_t. > > bb5547acfcd8 ("iommu/fsl: Make iova dma_addr_t in the iommu_iova_to_phys > API") did this for iommu_iova_to_phys(), but didn't fix the rest of the > IOMMU API.
This patch looks 100% correct, but I'm not convinced it's a good idea: On 32-bit platforms (i.e. most of the ones you change), doing 64-bit arithmetic has a noticeable overhead. I am not aware of an IOMMU that actually uses 64-bit DMA addresses on its slave side, usually they are used to translate addresses from 32-bit masters into 64-bit memory addresses, so using 'unsigned long' seems better from a practical point of view as opposed to the strict type correctness.
Arnd
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