Turn relaxed-fencing off by default for older (pre-G33) chipsets

There are still too many unresolved bugs, typically GPU hangs, that are
related to using relaxed fencing (i.e. only allocating the minimal
amount of memory required for a buffer) on older hardware, so turn off
the feature by default for the release.

Reported-and-tested-by: Knut Petersen <Knut_Petersen@t-online.de>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=36147
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 30 insertions, 6 deletions

diff --git a/src/intel_driver.c b/src/intel_driver.c
index 1b0d7404..e867351b 100644
--- a/src/intel_driver.c
+++ b/src/intel_driver.c
@@ -101,6 +101,7 @@ typedef enum {
    OPTION_DEBUG_FLUSH_CACHES,
    OPTION_DEBUG_WAIT,
    OPTION_HOTPLUG,
+   OPTION_RELAXED_FENCING,
 } I830Opts;
 
 static OptionInfoRec I830Options[] = {
@@ -121,6 +122,7 @@ static OptionInfoRec I830Options[] = {
    {OPTION_DEBUG_FLUSH_CACHES, "DebugFlushCaches", OPTV_BOOLEAN, {0}, FALSE},
    {OPTION_DEBUG_WAIT, "DebugWait", OPTV_BOOLEAN, {0}, FALSE},
    {OPTION_HOTPLUG,	"HotPlug",	OPTV_BOOLEAN,	{0},	TRUE},
+   {OPTION_RELAXED_FENCING,	"RelaxedFencing",	OPTV_BOOLEAN,	{0},	TRUE},
    {-1,			NULL,		OPTV_NONE,	{0},	FALSE}
 };
 /* *INDENT-ON* */
@@ -448,23 +450,33 @@ static void I830XvInit(ScrnInfoPtr scrn)
 		   intel->colorKey);
 }
 
-static Bool has_kernel_flush(struct intel_screen_private *intel)
+static Bool drm_has_boolean_param(struct intel_screen_private *intel,
+				  int param)
 {
 	drm_i915_getparam_t gp;
 	int value;
 
-	/* The BLT ring was introduced at the same time as the
-	 * automatic flush for the busy-ioctl.
-	 */
-
 	gp.value = &value;
-	gp.param = I915_PARAM_HAS_BLT;
+	gp.param = param;
 	if (drmIoctl(intel->drmSubFD, DRM_IOCTL_I915_GETPARAM, &gp))
 		return FALSE;
 
 	return value;
 }
 
+static Bool has_kernel_flush(struct intel_screen_private *intel)
+{
+	/* The BLT ring was introduced at the same time as the
+	 * automatic flush for the busy-ioctl.
+	 */
+	return drm_has_boolean_param(intel, I915_PARAM_HAS_BLT);
+}
+
+static Bool has_relaxed_fencing(struct intel_screen_private *intel)
+{
+	return drm_has_boolean_param(intel, I915_PARAM_HAS_RELAXED_FENCING);
+}
+
 static Bool can_accelerate_blt(struct intel_screen_private *intel)
 {
 	if (0 && (IS_I830(intel) || IS_845G(intel))) {
@@ -630,6 +642,18 @@ static Bool I830PreInit(ScrnInfoPtr scrn, int flags)
 			   " 2D GPU acceleration disabled.\n");
 	}
 
+	intel->has_relaxed_fencing =
+		xf86ReturnOptValBool(intel->Options,
+				     OPTION_RELAXED_FENCING,
+				     INTEL_INFO(intel)->gen >= 33);
+	/* And override the user if there is no kernel support */
+	if (intel->has_relaxed_fencing)
+		intel->has_relaxed_fencing = has_relaxed_fencing(intel);
+
+	xf86DrvMsg(scrn->scrnIndex, X_CONFIG,
+		   "Relaxed fencing %s\n",
+		   intel->has_relaxed_fencing ? "enabled" : "disabled");
+
 	/* SwapBuffers delays to avoid tearing */
 	intel->swapbuffers_wait = xf86ReturnOptValBool(intel->Options,
 						       OPTION_SWAPBUFFERS_WAIT,