drm/i915/guc: Add debug capture of GuC exception

Detect GuC firmware load failure due to an exception during execution
in GuC firmware. Output the GuC EIP where exception occurred to dmesg
for GuC debug information.

v2: correct typos, change debug message and error code returned for
GuC exception (Michal)
Signed-off-by: Robert M. Fosha <robert.m.fosha@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190625164107.21512-1-robert.m.fosha@intel.com

drivers/gpu/drm/i915/intel_guc_fw.c

@@ -197,6 +197,7 @@ static inline bool guc_ready(struct intel_guc *guc, u32 *status)
 
 static int guc_wait_ucode(struct intel_guc *guc)
 {
+	struct drm_i915_private *i915 = guc_to_i915(guc);
 	u32 status;
 	int ret;
 
@@ -216,6 +217,12 @@ static int guc_wait_ucode(struct intel_guc *guc)
 		ret = -ENOEXEC;
 	}
 
+	if ((status & GS_UKERNEL_MASK) == GS_UKERNEL_EXCEPTION) {
+		DRM_ERROR("GuC firmware exception. EIP: %#x\n",
+			  intel_uncore_read(&i915->uncore, SOFT_SCRATCH(13)));
+		ret = -ENXIO;
+	}
+
 	if (ret == 0 && !guc_xfer_completed(guc, &status)) {
 		DRM_ERROR("GuC is ready, but the xfer %08x is incomplete\n",
 			  status);

drivers/gpu/drm/i915/intel_guc_reg.h

@@ -37,6 +37,7 @@
 #define   GS_UKERNEL_MASK		  (0xFF << GS_UKERNEL_SHIFT)
 #define   GS_UKERNEL_LAPIC_DONE		  (0x30 << GS_UKERNEL_SHIFT)
 #define   GS_UKERNEL_DPC_ERROR		  (0x60 << GS_UKERNEL_SHIFT)
+#define   GS_UKERNEL_EXCEPTION		  (0x70 << GS_UKERNEL_SHIFT)
 #define   GS_UKERNEL_READY		  (0xF0 << GS_UKERNEL_SHIFT)
 #define   GS_MIA_SHIFT			16
 #define   GS_MIA_MASK			  (0x07 << GS_MIA_SHIFT)