drm/xe: Add helper to capture engine timestamp

Just like CTX_TIMESTAMP is used to calculate runtime, add a helper to
get the timestamp for the engine so it can be used to calculate the
"engine time" with the same unit as the runtime is recorded.
Reviewed-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240517204310.88854-5-lucas.demarchi@intel.comSigned-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

drivers/gpu/drm/xe/xe_hw_engine.c

@@ -1121,3 +1121,8 @@ const char *xe_hw_engine_class_to_str(enum xe_engine_class class)
 
 	return NULL;
 }
+
+u64 xe_hw_engine_read_timestamp(struct xe_hw_engine *hwe)
+{
+	return xe_mmio_read64_2x32(hwe->gt, RING_TIMESTAMP(hwe->mmio_base));
+}

drivers/gpu/drm/xe/xe_hw_engine.h

@@ -68,5 +68,6 @@ static inline bool xe_hw_engine_is_valid(struct xe_hw_engine *hwe)
 }
 
 const char *xe_hw_engine_class_to_str(enum xe_engine_class class);
+u64 xe_hw_engine_read_timestamp(struct xe_hw_engine *hwe);
 
 #endif