drm/i915/guc: Fix a bug in GuC status check

Bit 16 of GuC status indicates resuming from RC6. The LAPIC_DONE
status is a reliable readiness flag only when resuming from RC6.
This fix a racing issue that allocation of doorbell fails whilst
GuC init is not finished.

Signed-off-by: Alex Dai <yu.dai@intel.com>
Reviewed-by: Sagar Arun Kamble <sagar.a.kamble@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_guc_reg.h

@@ -37,6 +37,7 @@
 #define   GS_UKERNEL_READY		  (0xF0 << GS_UKERNEL_SHIFT)
 #define   GS_MIA_SHIFT			16
 #define   GS_MIA_MASK			  (0x07 << GS_MIA_SHIFT)
+#define   GS_MIA_CORE_STATE		  (1 << GS_MIA_SHIFT)
 
 #define SOFT_SCRATCH(n)			(0xc180 + ((n) * 4))
 

drivers/gpu/drm/i915/intel_guc_loader.c

@@ -209,9 +209,10 @@ static inline bool guc_ucode_response(struct drm_i915_private *dev_priv,
 				      u32 *status)
 {
 	u32 val = I915_READ(GUC_STATUS);
+	u32 uk_val = val & GS_UKERNEL_MASK;
 	*status = val;
-	return ((val & GS_UKERNEL_MASK) == GS_UKERNEL_READY ||
-		(val & GS_UKERNEL_MASK) == GS_UKERNEL_LAPIC_DONE);
+	return (uk_val == GS_UKERNEL_READY ||
+		((val & GS_MIA_CORE_STATE) && uk_val == GS_UKERNEL_LAPIC_DONE));
 }
 
 /*