Re: [RFC 0/4] Add NVIDIA Tegra DRM support

[Alan Cox <alan-qBU/x9rampVanCEyBjwyrvXRex20P6io@public.gmane.org>]

On Wed, 11 Apr 2012 14:10:26 +0200
Thierry Reding <thierry.reding-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org> wrote:

> This series adds a basic DRM driver for NVIDIA Tegra 2 processors. It
> currently only supports the RGB output and I've successfully tested it
> against the fbcon kernel module and the xf86-video-modesetting driver.
> The code uses the Tegra's IOMMU/GART to remap non-contiguous memory.
> This means that currently video memory is limited to 32 MB, the size of
> the GART aperture.

You should only need continguous memory with GEM for the framebuffer /
console bits via /dev/fb. In theory the fb layer can be taught to hanndle
non linear framebuffers but nobody has yet done so. (Now there's a GSOC
project ... ;))

What we do on GMA500 is to allocate the kernel framebuffer from linearly
mapped memory but the normal GEM objects from anywhere as the GEM mapping
into userspace will deal with presenting it to user space as a virtually
linear buffer.

Alan