cpu/topology: Export die_id

Export die_id in cpu topology, for the benefit of hardware that has
multiple-die/package.
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: linux-doc@vger.kernel.org
Link: https://lkml.kernel.org/r/e7d1caaf4fbd24ee40db6d557ab28d7d83298900.1557769318.git.len.brown@intel.com

Documentation/cputopology.txt

@@ -12,6 +12,12 @@ physical_package_id:
 	socket number, but the actual value is architecture and platform
 	dependent.
 
+die_id:
+
+	the CPU die ID of cpuX. Typically it is the hardware platform's
+	identifier (rather than the kernel's).  The actual value is
+	architecture and platform dependent.
+
 core_id:
 
 	the CPU core ID of cpuX. Typically it is the hardware platform's
@@ -81,6 +87,7 @@ For an architecture to support this feature, it must define some of
 these macros in include/asm-XXX/topology.h::
 
 	#define topology_physical_package_id(cpu)
+	#define topology_die_id(cpu)
 	#define topology_core_id(cpu)
 	#define topology_book_id(cpu)
 	#define topology_drawer_id(cpu)
@@ -99,9 +106,11 @@ provides default definitions for any of the above macros that are
 not defined by include/asm-XXX/topology.h:
 
 1) topology_physical_package_id: -1
-2) topology_core_id: 0
-3) topology_sibling_cpumask: just the given CPU
-4) topology_core_cpumask: just the given CPU
+2) topology_die_id: -1
+3) topology_core_id: 0
+4) topology_sibling_cpumask: just the given CPU
+5) topology_core_cpumask: just the given CPU
+6) topology_die_cpumask: just the given CPU
 
 For architectures that don't support books (CONFIG_SCHED_BOOK) there are no
 default definitions for topology_book_id() and topology_book_cpumask().

drivers/base/topology.c

@@ -43,6 +43,9 @@ static ssize_t name##_list_show(struct device *dev,			\
 define_id_show_func(physical_package_id);
 static DEVICE_ATTR_RO(physical_package_id);
 
+define_id_show_func(die_id);
+static DEVICE_ATTR_RO(die_id);
+
 define_id_show_func(core_id);
 static DEVICE_ATTR_RO(core_id);
 
@@ -72,6 +75,7 @@ static DEVICE_ATTR_RO(drawer_siblings_list);
 
 static struct attribute *default_attrs[] = {
 	&dev_attr_physical_package_id.attr,
+	&dev_attr_die_id.attr,
 	&dev_attr_core_id.attr,
 	&dev_attr_thread_siblings.attr,
 	&dev_attr_thread_siblings_list.attr,

include/linux/topology.h

@@ -184,6 +184,9 @@ static inline int cpu_to_mem(int cpu)
 #ifndef topology_physical_package_id
 #define topology_physical_package_id(cpu)	((void)(cpu), -1)
 #endif
+#ifndef topology_die_id
+#define topology_die_id(cpu)			((void)(cpu), -1)
+#endif
 #ifndef topology_core_id
 #define topology_core_id(cpu)			((void)(cpu), 0)
 #endif