susetting the remaining swioltb couplin in DRM

[Rodrigo Vivi]

On Mon, Jul 11, 2022 at 10:26:14AM +0200, Christoph Hellwig wrote:
> Hi i915 and nouveau maintainers,
> 
> any chance I could get some help to remove the remaining direct
> driver calls into swiotlb, namely swiotlb_max_segment and
> is_swiotlb_active.  Either should not matter to a driver as they
> should be written to the DMA API.

Hi Christoph,

while we take a look here, could you please share the reasons
behind sunsetting this calls?

> 
> In the i915 case it seems like the driver should use
> dma_alloc_noncontiguous and/or dma_alloc_noncoherent to allocate
> DMAable memory instead of using alloc_page and the streaming
> dma mapping helpers.
> 
> For the latter it seems like it should just stop passing
> use_dma_alloc == true to ttm_device_init and/or that function
> should switch to use dma_alloc_noncoherent.