st/nine: Default tearfree_discard to true

With tearfree_discard=false, we tear when rendering
fullscreen apps with vsync off.

This is a feature in the sense it's the same as the native
implementation. This also means lower input lag.

However I think most users will prefer to have no tearing,
and don't care about sub refresh-rate input lag.

Thus it's better to default tearfree_discard to true.

Signed-off-by: Axel Davy <davyaxel0@gmail.com>
Acked-by: Timur Kristóf <timur.kristof@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10160>

src/gallium/targets/d3dadapter9/drm.c

@@ -56,7 +56,7 @@ const driOptionDescription __driConfigOptionsNine[] = {
         DRI_CONF_NINE_THROTTLE(-2)
         DRI_CONF_NINE_THREADSUBMIT(true)
         DRI_CONF_NINE_ALLOWDISCARDDELAYEDRELEASE(true)
-        DRI_CONF_NINE_TEARFREEDISCARD(false)
+        DRI_CONF_NINE_TEARFREEDISCARD(true)
         DRI_CONF_NINE_CSMT(-1)
         DRI_CONF_NINE_DYNAMICTEXTUREWORKAROUND(true)
         DRI_CONF_NINE_SHADERINLINECONSTANTS(false)

src/util/driconf.h

@@ -400,7 +400,7 @@
 
 #define DRI_CONF_NINE_TEARFREEDISCARD(def) \
    DRI_CONF_OPT_B(tearfree_discard, def, \
-                  "Whether to make d3d's presentation mode DISCARD (games usually use that mode) Tear Free. If rendering above screen refresh, some frames will get skipped. false by default.")
+                  "Whether to make d3d's presentation mode DISCARD (games usually use that mode) Tear Free. If rendering above screen refresh, some frames will get skipped. true by default.")
 
 #define DRI_CONF_NINE_CSMT(def) \
    DRI_CONF_OPT_I(csmt_force, def, 0, 0, \