Messages in this thread | | | Subject | Re: [PATCH V2 1/3] scsi: mptxsas: try 64 bit DMA when 32 bit DMA fails | From | Timur Tabi <> | Date | Tue, 10 Nov 2015 15:03:59 -0600 |
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On 11/10/2015 01:13 PM, Arnd Bergmann wrote: > If the mask is 64-bit by default on ARM64, that is a bug that we need > to fix urgently. Can you verify this?
I think the mask is 0 by default, because there's no code in ARM64 that actually sets the mask.
Take a look at arch_setup_pdev_archdata() in arch/powerpc/kernel/setup-common.c.
void arch_setup_pdev_archdata(struct platform_device *pdev) { pdev->archdata.dma_mask = DMA_BIT_MASK(32); pdev->dev.dma_mask = &pdev->archdata.dma_mask; set_dma_ops(&pdev->dev, &dma_direct_ops); }
I don't see anything equivalent in arch/arm64
> A lot of PCI devices can only do 32-bit DMA, and we have plenty > of drivers that don't bother setting a mask at all because the 32-bit > mask is the default on all other architectures.
In our drivers for 32-bit devices, we have to explicitly set the DMA mask to 32-bits in order to get any DMA working.
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