[Nouveau] Fixes and workarounds for regressions and issues in the randr-1.2 branch

[Bernhard Kaindl]

On Mon, 3 Sep 2007, Bernhard Kaindl wrote:
>
> They may help others as well but may e.g. also disable the Xv blitter
> which might be working for some (but didn't on my card) - more information
> is found in the text comments in the patches.

The patch "xf86-video-nouveau-Xv_noblit.diff" which disabled the Xv blitter
on some cards was wrong, thanks to encouragement from Arthur Huillet and that
I had now some time to check out what was failing, I found out that the Xv
problems which I see are limited to two situations:

1) randr active and monitors configured side-by-side with xrandr

2) Option "ShadowFB" is used (or other NoAccel trigger)

While I have no fix for 1) yet, 2) is easy to deal with properly:

As driving the blitter requires the DMA FIFO, and while the overlay might work
without the DMA FIFO, it has a fallback to the blitter for Composite, we think
it's best to also disable the overlay for now when pNV->NoAccel is <> 0.

I attached and appended patch for the current master branch, which (with one
small change, which I am going to talk in a separate mail) works for me with
Randr12 (except for the Xv in side-by-side mode).

Thanks to Arthur for the guidance and explanations!

Bernhard

--- src/nv_video.c	2007-09-05 16:02:00.000000000 +0200
+++ src/nv_video.c	2007-09-05 16:24:22.000000000 +0200
@@ -2275,10 +2275,13 @@
  	XF86VideoAdaptorPtr  blitAdaptor = NULL;
  	int                  num_adaptors;

-	if (pScrn->bitsPerPixel == 8)
-		return;
-
-	if (pNv->Architecture < NV_ARCH_50) {
+	/*
+	 * Driving the blitter requires the DMA FIFO. Using the FIFO
+	 * without accel causes DMA errors. While the overlay might
+	 * might work without accel, we also disable it for now when
+	 * acceleration is disabled:
+	 */
+	if (pScrn->bitsPerPixel != 8 && pNv->Architecture < NV_ARCH_50 && !pNv->NoAccel) {
  		overlayAdaptor = NVSetupOverlayVideo(pScreen);
  		blitAdaptor    = NVSetupBlitVideo(pScreen);
  	}
======================================================

PS: 
The inspiration to change from this logic

-       if (pScrn->bitsPerPixel == 8)
-               return;

to this logic

+       if (pScrn->bitsPerPixel != 8 && pNv->Architecture < NV_ARCH_50 && !pNv->NoAccel)
                 overlayAdaptor = NVSetupOverlayVideo(pScreen);
                 blitAdaptor    = NVSetupBlitVideo(pScreen);
         }

to disable overlay and blitter came from the NV50 change (which you see in the
patch) and it seems reasonable to do it also for 8bit as
xf86-video-intel-2.1.1/src/i810_video.c does it similar for 8bit:

     if (pScrn->bitsPerPixel != 8)
     {
         newAdaptor = I810SetupImageVideo(pScreen);
         I810InitOffscreenImages(pScreen);
     }

     num_adaptors = xf86XVListGenericAdaptors(pScrn, &adaptors);

     if(newAdaptor) {
... similar to nouveau code here
     }

     if(num_adaptors)
         xf86XVScreenInit(pScreen, adaptors, num_adaptors);

(The routine in nv_driver has basically the same code)

which means that generic, driver-independent Xv adaptors (such as the v4l Xv
adaptor) are always initialized, xf86XVListGenericAdaptors lists them if
such are there:

xf86XVListGenericAdaptors(
...
     /*
      * The v4l driver registers itself first, but can use surfaces registered
      * by other drivers.  So, call the v4l driver last.
      */
..
}
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