bsp/powerpc: Move libcpu timer to bsps

Use only one timer driver variant based on the standard PowerPC time
base.

This patch is a part of the BSP source reorganization.

Update #3285.

bsps/powerpc/shared/ppc-dec-timer.c

@@ -0,0 +1,88 @@
+/**
+ *  @file
+ *  @brief
+ *
+ *  This file implements a benchmark timer using the PPC Timebase Register.
+ */
+
+/*
+ *  COPYRIGHT (c) 1989-2014.
+ *  On-Line Applications Research Corporation (OAR).
+ *
+ *  The license and distribution terms for this file may in
+ *  the file LICENSE in this distribution or at
+ *  http://www.rtems.org/license/LICENSE.
+ */
+
+#include <bsp.h>
+#include <rtems.h>
+#include <rtems/system.h>
+#include <rtems/btimer.h>
+#include <assert.h>
+#include <libcpu/powerpc-utility.h>
+
+#ifndef BSP_Convert_decrementer
+#define BSP_Convert_decrementer(value) (value)
+#endif
+
+uint64_t   Timer_driver_Start_time;
+
+bool benchmark_timer_find_average_overhead = false;
+unsigned clicks_overhead = 0;
+
+/*
+ * Timer Get overhead
+ */
+static int Timer_get_clicks_overhead(void)
+{
+  uint64_t    clicks;
+
+  PPC_Set_timebase_register((uint64_t) 0);
+  clicks = PPC_Get_timebase_register();
+  assert(clicks <= 0xffffffff);
+  clicks_overhead = (unsigned) clicks;
+  return clicks_overhead;
+}
+
+/*
+ * benchmark_timer_initialize
+ */
+void benchmark_timer_initialize(void)
+{
+
+  /*
+   *  Timer runs long and accurate enough not to require an interrupt.
+   */
+
+  if (clicks_overhead == 0) clicks_overhead = Timer_get_clicks_overhead();
+  PPC_Set_timebase_register((uint64_t) 0);
+}
+
+
+/*
+ *  benchmark_timer_read
+ */
+
+benchmark_timer_t benchmark_timer_read(void)
+{
+  uint64_t    total64;
+  uint32_t    total;
+
+  /* approximately CLOCK_SPEED clicks per microsecond */
+
+  total64 = PPC_Get_timebase_register();
+
+  assert( total64 <= 0xffffffff );  /* fits into a uint32_t   */
+
+  total = (uint32_t) total64;
+
+  if ( benchmark_timer_find_average_overhead == true )
+    return total;          /* in "clicks" of the decrementer units */
+
+  return (int) BSP_Convert_decrementer(total - clicks_overhead);
+}
+
+void benchmark_timer_disable_subtracting_average_overhead(bool find_flag)
+{
+  benchmark_timer_find_average_overhead = find_flag;
+}