powerpc: Add _CPU_Get_current_per_CPU_control()

Add _CPU_Get_current_per_CPU_control() on SMP configurations.  Use SPRG0
for the current per-CPU control.  This reduces the code size by three
instructions and is slightly faster.

Update #2805.

c/src/lib/libbsp/powerpc/qoriq/start/start.S

@@ -182,6 +182,10 @@ _start:
 	/* Set small-data anchor */
 	LA	r13, _SDA_BASE_
 
+#ifdef RTEMS_SMP
+	SET_SELF_CPU_CONTROL	r4
+#endif
+
 	blr
 
 .Linitmore:

c/src/lib/libcpu/powerpc/shared/include/powerpc-utility.h

@@ -936,13 +936,20 @@ void ShowBATS(void);
 	mtmsr	\level
 .endm
 
-.macro GET_SELF_CPU_CONTROL reg
 #if defined(RTEMS_SMP)
+.macro SET_SELF_CPU_CONTROL reg
 	/* Use Book E Processor ID Register (PIR) */
 	mfspr	\reg, 286
 	slwi	\reg, \reg, PER_CPU_CONTROL_SIZE_LOG2
 	addis	\reg, \reg, _Per_CPU_Information@ha
 	addi	\reg, \reg, _Per_CPU_Information@l
+	mtspr	PPC_PER_CPU_CONTROL_REGISTER, \reg
+.endm
+#endif
+
+.macro GET_SELF_CPU_CONTROL reg
+#if defined(RTEMS_SMP)
+	mfspr	\reg, PPC_PER_CPU_CONTROL_REGISTER
 #else
 	lis	\reg, _Per_CPU_Information@h
 	ori	\reg, \reg, _Per_CPU_Information@l

cpukit/score/cpu/powerpc/rtems/score/cpuimpl.h

@@ -5,6 +5,8 @@
  */
 
 /*
+ * Copyright (c) 2016 embedded brains GmbH
+ *
  * The license and distribution terms for this file may be
  * found in the file LICENSE in this distribution or at
  * http://www.rtems.org/license/LICENSE.
@@ -15,12 +17,37 @@
 
 #include <rtems/score/cpu.h>
 
+#ifdef RTEMS_SMP
+
+/* Use SPRG0 for the per-CPU control of the current processor */
+#define PPC_PER_CPU_CONTROL_REGISTER 272
+
+#endif /* RTEMS_SMP */
+
 #ifndef ASM
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#ifdef RTEMS_SMP
+
+static inline struct Per_CPU_Control *_PPC_Get_current_per_CPU_control( void )
+{
+  struct Per_CPU_Control *cpu_self;
+
+  __asm__ volatile (
+    "mfspr %0, " RTEMS_XSTRING( PPC_PER_CPU_CONTROL_REGISTER )
+    : "=r" ( cpu_self )
+  );
+
+  return cpu_self;
+}
+
+#define _CPU_Get_current_per_CPU_control() _PPC_Get_current_per_CPU_control()
+
+#endif /* RTEMS_SMP */
+
 #ifdef __cplusplus
 }
 #endif