Messages in this thread | | | Date | Tue, 28 Aug 2018 13:55:03 +0100 | From | Catalin Marinas <> | Subject | Re: Query on dma_set_mask_and_coherent() Usage |
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On Thu, Aug 23, 2018 at 08:20:36PM +0530, Kedareswararao Appana wrote: > On arm64 platform I have booted Linux only with > 32-bit > Address i.e from 0x800000000 (reg = <0x8 0x00000000 0x0 0x80000000>)
So you have 2GB of RAM starting at 0x8_0000_0000.
> In my driver, I am using dma_set_mask_and_coherent(&pdev->dev, > DMA_BIT_MASK(32)); which should fail if I boot Linux > with the above configuration but the API is returning success. > > I have debugged it further and observed that, in the arm64 > dma-mapping.c swiotlb is zero resulting dma_supported ops always > returning 1 > > https://elixir.bootlin.com/linux/v4.17.8/source/arch/arm64/mm/dma-mapping.c#L321 > > I will be grateful if someone can send me some pointers for fixing this issue
It's an assumption we've made here:
https://elixir.bootlin.com/linux/v4.17.8/source/arch/arm64/mm/init.c#L224
32-bit devices are expected to have a dma_pfn_offset (and the hardware configured accordingly).
-- Catalin
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