ColorTiling breaks output on G5

[Benjamin Herrenschmidt]

Hi !

I haven't tested on other ppc / big endian machines, but the color
tiling option definitely breaks the output on the G5 here. The setup
is a G5 running debian/ppc with a 32 bits Xorg build (CVS from an hour
ago), a Radeon 9600 AGP, no DRM, single head on primary TMDS output,
1280x1024 TFT flat panel.

With Option "ColorTiling" "off" it works fine, but when "on", I get
something a bit strange (I would need a digital camera...). The cursor
is fine, and the gray pattern looks like vertical stripes, slightly
ondulating, something like:

 *   *   *  * *   *   *        *   * ...
 *   *   *  * *   *   *        *   * ...
 *   *   *  * *   *   *        *   * ...
 *   *   *  * *   *   *        *   * ...
  *   *   *  * *   *   *      *   * ...
  *   *   *  * *   *   *      *   * ...
  *   *   *  * *   *   *      *   * ...
  *   *   *  * *   *   *      *   * ...
 *   *   *  * *   *   *        *   * ...
 *   *   *  * *   *   *        *   * ...
 *   *   *  * *   *   *        *   * ...
 *   *   *  * *   *   *        *   * ...
  *   *   *  * *   *   *      *   * ...
  *   *   *  * *   *   *      *   * ...
  *   *   *  * *   *   *      *   * ...
  *   *   *  * *   *   *      *   * ...
 *   *   *  * *   *   *        *   * ...
 *   *   *  * *   *   *        *   * ...
 *   *   *  * *   *   *        *   * ...
 *   *   *  * *   *   *        *   * ...

etc....

I don't fully understand what the tiling is (quick explanation
welcome !) so I haven't looked into fixing it yet.

Ben.