Implementing Render acceleration in the siliconmotion driver

[Alex Deucher]

On Wed, Aug 20, 2008 at 11:12 AM,  <currojerez at gmail.com> wrote:
> Hi,
> I have been experimenting with the sm720 3d engine: I thought I
> could implement EXA composite acceleration in this hardware but
> it seems to have several drawbacks.
>
> The triangle engine worked more or less as expected, but the texture
> engine only works when fed with images arranged in 16B*8 tiles (this
> isn't mentioned in the documentation provided by smi:
> ftp://ftp.siliconmotion.com.tw/databooks/ . In fact, the word "tile"
> doesn't appear a single time in the datasheet).
> This wouldn't be a problem if the rest of graphic subsystems supported
> tiled data, or if the conversion could be done in hardware, but it
> isn't the case.
> The sm722 seems to have the same problem. The sm731 (Cougar3DR) drawing
> engine and video processor seem to support tiled pixmaps, but I don't
> think I could implement it without access to the hardware.
>

I wonder if there is some sort of aperture or surface control that
will do the translation for you.  That's how most hardware with tiled
surfaces works.

> The second texture engine would be useful to implement masks, but I
> can't get it working, it has all the necessary registers, but I don't
> think it really has two texture engines ( From the manual: "Trilinear
> mip-mapping and texture compositing (multiple texture map) are done in
> 2 passes.").
>

As Roland noted the hw probably handles this internally.

> Moreover, it doesn't support any texture format like PICT_a8, I think
> (please, correct me if i'm wrong) it is used intensively for things
> like antialiased fonts, and it would be one of the main things
> composite would accelerate.

Seems to support a CI8 texture format.

> Probably PICT_a8 masks could be converted in hardware to ARGB, but I
> don't think anymore an efficient composite implementation could be
> written for this hardware.
> Any ideas?

the mach64 driver has similar hardware limitations and has a certain
degree of render accel:
http://cgit.freedesktop.org/xorg/driver/xf86-video-mach64/tree/src/atimach64render.c

Alex