Re: [PATCH V11 3/5] i2c: tegra: Add DMA support

[Christoph Hellwig]

On Wed, Feb 06, 2019 at 05:56:02PM +0300, Dmitry Osipenko wrote:
> > We don't have an IOMMU attached to I2C or APBDMA, so this can't happen
> > and even if we had an IOMMU attached, all we care about is the device's
> > DMA address space, which means IOVA space, and that would still be
> > guaranteed to be contiguous, according to the above.
> 
> Yes, but doesn't T186+ have IOMMU support for the DMA controller?

Even if it did, why would that matter?  The device would only see
IOVA space, the CPU for a normal driver only sees kernel virtual
space.

Forced contiguous space only makes sense when you have access by CPU
physical address, which should not happen for "normal" device drivers.