On Wed, Sep 23, 2020 at 08:48:26AM +0200, Marek Szyprowski wrote:
> Hi Shaik,
> 
> I've run into similar problem while adapting S5P-MFC and Exynos4-IS 
> drivers for generic IOMMU-DMA framework. Here is my first solution: 
> https://lore.kernel.org/linux-samsung-soc/20200918144833.14618-1-m.szyprow...@samsung.com/T/
>  
> 
> 
> It allows to remap given buffer at the specific IOVA address, although 
> it doesn't guarantee that those specific addresses won't be later used 
> by the IOVA allocator. Probably it would make sense to add an API for 
> generic IOMMU-DMA framework to mark the given IOVA range as 
> reserved/unused to protect them.

If you want to use IOVA addresses in a device otherwise managed by
dma-iommu we need to expose an API through the dma API.  Can you please
include the iommu list in the discussion of your series?

I don't think using the raw IOMMU API is a very idea in these drivers,
we probably want a way to change the allocator algorithm or hint the
next IOVA and keep using the normal DMA API.  Maybe Robin has a better
idea.
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