[RFC 4/4] drm: Add NVIDIA Tegra support

Daniel Vetter daniel at ffwll.ch
Wed Apr 11 06:35:12 PDT 2012

On Wed, Apr 11, 2012 at 03:23:26PM +0200, Thierry Reding wrote:
> * Daniel Vetter wrote:
> > On Wed, Apr 11, 2012 at 02:10:30PM +0200, Thierry Reding wrote:
> > > This commit adds a very basic DRM driver for NVIDIA Tegra SoCs. It
> > > currently has rudimentary GEM support and can run a console on the
> > > framebuffer as well as X using the xf86-video-modesetting driver.
> > > Only the RGB output is supported. Quite a lot of things still need
> > > to be worked out and there is a lot of room for cleanup.
> > 
> > Indeed, after a quick look there are tons of functions that are just stubs
> > ;-) One thing I wonder though is why you directly use the iommu api and
> > not wrap it up into dma_map? Is arm infrastructure just not there yet or
> > do you plan to tightly integrate the tegra drm with the iommu (e.g. for
> > process space switching or similarly funky stuff)?
> I'm not sure I know what you are referring to. Looking for all users of
> iommu_map() doesn't turn up anything related to dma_map. Can you point me in
> the right direction?

Well, you use the iommu api to map/unmap memory into the iommu for tegra,
whereas usually device drivers just use the dma api to do that. The usual
interface is dma_map_sg/dma_unmap_sg, but there are quite a few variants
around. I'm just wondering why this you've choosen this.
Daniel Vetter
Mail: daniel at ffwll.ch
Mobile: +41 (0)79 365 57 48

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