drm/i915: Shortcut readiness to reset check

If the engine says it is ready for reset, it is ready
so avoid further dancing and proceed.

v2: reg (Chris)
v3: request, ack, mask from following patch (Chris)

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190412165335.16347-1-mika.kuoppala@linux.intel.com

drivers/gpu/drm/i915/i915_reset.c

@@ -490,20 +490,26 @@ static int gen11_reset_engines(struct drm_i915_private *i915,
 static int gen8_engine_reset_prepare(struct intel_engine_cs *engine)
 {
 	struct intel_uncore *uncore = engine->uncore;
+	const i915_reg_t reg = RING_RESET_CTL(engine->mmio_base);
+	u32 request, mask, ack;
 	int ret;
 
-	intel_uncore_write_fw(uncore,
-			      RING_RESET_CTL(engine->mmio_base),
-			      _MASKED_BIT_ENABLE(RESET_CTL_REQUEST_RESET));
+	ack = intel_uncore_read_fw(uncore, reg);
+	if (!(ack & RESET_CTL_READY_TO_RESET)) {
+		request = RESET_CTL_REQUEST_RESET;
+		mask = RESET_CTL_READY_TO_RESET;
+		ack = RESET_CTL_READY_TO_RESET;
+	} else {
+		return 0;
+	}
 
-	ret = __intel_wait_for_register_fw(uncore,
-					   RING_RESET_CTL(engine->mmio_base),
-					   RESET_CTL_READY_TO_RESET,
-					   RESET_CTL_READY_TO_RESET,
-					   700, 0,
-					   NULL);
+	intel_uncore_write_fw(uncore, reg, _MASKED_BIT_ENABLE(request));
+	ret = __intel_wait_for_register_fw(uncore, reg, mask, ack,
+					   700, 0, NULL);
 	if (ret)
-		DRM_ERROR("%s: reset request timeout\n", engine->name);
+		DRM_ERROR("%s reset request timed out: {request: %08x, RESET_CTL: %08x}\n",
+			  engine->name, request,
+			  intel_uncore_read_fw(uncore, reg));
 
 	return ret;
 }