Disable frame buffer compression by default for GM965.

We haven't found a way to make FBC work reliably with GM965 yet,
(it often fails to notice CPU writes). This appears to be a
specific problem with this device, (as we haven't gotten similar
bug reports for subsequent devices such as GM45). So FBC is
now disabled by default for GM965 but can still be enabled with
the FrameBufferCompression option for experimenting/debugging.

This resolves bug #16257:

	[GM965 EXA] Frame-buffer compression broken for CPU writes (XPutImage)
	https://bugs.freedesktop.org/show_bug.cgi?id=16257

1 files changed, 7 insertions, 0 deletions

diff --git a/src/i830.h b/src/i830.h
index 5b782369..89f19d20 100644
--- a/src/i830.h
+++ b/src/i830.h
@@ -950,6 +950,13 @@ static inline int i830_fb_compression_supported(I830Ptr pI830)
      */
     if (!pI830->tiling || (IS_I965G(pI830) && pI830->accel <= ACCEL_XAA))
 	return FALSE;
+    /* We have not gotten FBC to work consistently on 965GM. Our best
+     * working theory right now is that FBC simply isn't reliable on
+     * that device. See this bug report for more details:
+     * https://bugs.freedesktop.org/show_bug.cgi?id=16257
+     */
+    if (IS_I965GM(pI830))
+	return FALSE;
     return TRUE;
 }