etnaviv: Hide MSAA support behind debug flag

With the current level of MSAA support we have some real world rendering
problems in Chromium/Skia (issue #7678). Convert the MSAA support to an
explicit opt-in by settings ETNA_MESA_DEBUG=msaa.

Cc: 22.3 mesa-stable
Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19870>
(cherry picked from commit 4f5e59d114)

.pick_status.json

@@ -2092,7 +2092,7 @@
         "description": "etnaviv: Hide MSAA support behind debug flag",
         "nominated": true,
         "nomination_type": 0,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": null
     },

src/gallium/drivers/etnaviv/etnaviv_debug.h

@@ -55,6 +55,7 @@
 #define ETNA_DBG_DEQP            0x800000 /* Hacks to run dEQP GLES3 tests */
 #define ETNA_DBG_NOCACHE         0x1000000 /* Disable shader cache */
 #define ETNA_DBG_NO_LINEAR_PE    0x2000000 /* Disable linear PE */
+#define ETNA_DBG_MSAA            0x4000000 /* Enable MSAA */
 
 extern int etna_mesa_debug; /* set in etnaviv_screen.c from ETNA_MESA_DEBUG */
 

src/gallium/drivers/etnaviv/etnaviv_screen.c

@@ -73,6 +73,7 @@ static const struct debug_named_value etna_debug_options[] = {
    {"deqp",           ETNA_DBG_DEQP, "Hacks to run dEQP GLES3 tests"}, /* needs MESA_GLES_VERSION_OVERRIDE=3.0 */
    {"nocache",        ETNA_DBG_NOCACHE,    "Disable shader cache"},
    {"no_linear_pe",   ETNA_DBG_NO_LINEAR_PE, "Disable linear PE"},
+   {"msaa",           ETNA_DBG_MSAA, "Enable MSAA support"},
    DEBUG_NAMED_VALUE_END
 };
 
@@ -496,6 +497,10 @@ gpu_supports_render_format(struct etna_screen *screen, enum pipe_format format,
       return false;
 
    if (sample_count > 1) {
+      /* Explicitly enabled. */
+      if (!DBG_ENABLED(ETNA_DBG_MSAA))
+         return false;
+
       /* The hardware supports it. */
       if (!VIV_FEATURE(screen, chipFeatures, MSAA))
          return false;