3 files changed, 53 insertions, 0 deletions

diff --git a/arch/arm/include/asm/timex.h b/arch/arm/include/asm/timex.h
index 8a102a383a36..12a53699cd20 100644
--- a/arch/arm/include/asm/timex.h
+++ b/arch/arm/include/asm/timex.h
@@ -16,6 +16,17 @@
 
 typedef unsigned long cycles_t;
 
+#if defined(CONFIG_CPU_V7) && !defined(CONFIG_HW_PERF_EVENTS)
+static inline cycles_t v7_get_cycles (void)
+{
+        u32 value;
+        /* read CCNT register */
+        asm volatile("mrc p15, 0, %0, c9, c13, 0" : "=r"(value));
+        return value;
+}
+#define get_cycles v7_get_cycles
+#endif
+
 #ifndef get_cycles
 static inline cycles_t get_cycles (void)
 {
diff --git a/litmus/color.c b/litmus/color.c
index 976366e7e39c..278f541e07c1 100644
--- a/litmus/color.c
+++ b/litmus/color.c
@@ -340,6 +340,12 @@ out:
         return err;
 }
 
+static void __init print_cycle_count(void *_unused)
+{
+        cycles_t cycles = get_cycles();
+        printk("CPU %2d: %10lu cycles\n", smp_processor_id(), cycles);
+}
+
 static int __init init_color(void)
 {
         int err = 0;
@@ -354,6 +360,11 @@ static int __init init_color(void)
 
         BUG_ON(LOCKDEP_MAX_NR_COLORS < color_cache_info.nr_colors);
         err = init_color_groups();
+
+        printk("Cycle counter test:\n");
+        print_cycle_count(NULL);
+        smp_call_function(print_cycle_count, NULL, 0);
+
         return err;
 }
 
diff --git a/litmus/litmus.c b/litmus/litmus.c
index 1bbad8db1a55..531a2245133d 100644
--- a/litmus/litmus.c
+++ b/litmus/litmus.c
@@ -656,6 +656,35 @@ static struct sysrq_key_op sysrq_kill_rt_tasks_op = {
 
 extern struct sched_plugin linux_sched_plugin;
 
+#if defined(CONFIG_CPU_V7) && !defined(CONFIG_HW_PERF_EVENTS)
+static void __init litmus_enable_perfcounters_v7(void *_ignore)
+{
+        u32 enable_val;
+
+        /* write 1 to enable user-mode access to the performance counter */
+        asm volatile("mcr p15, 0, %0, c9, c14, 0" : : "r" (1));
+
+        /* disable counter overflow interrupts (just in case) */
+        asm volatile("mcr p15, 0, %0, c9, c14, 2" : : "r" (0x8000000f));
+
+        enable_val = 1;         /* bit 1 enables the counters */
+        enable_val |= 2;        /* resets cycle counter to zero */
+        /* performance monitor control register: enable all counters */
+        asm volatile("mcr p15, 0, %0, c9, c12, 0" : : "r"(enable_val));
+
+        /* enables counters (currently just cycle counter) */
+        asm volatile("mcr p15, 0, %0, c9, c12, 1" : : "r"(0x80000000));
+}
+
+static void __init litmus_enable_perfcounters(void)
+{
+        litmus_enable_perfcounters_v7(NULL);
+        smp_call_function(litmus_enable_perfcounters_v7, NULL, 0);
+}
+#else
+#define litmus_enable_perfcounters() do { } while (0)
+#endif
+
 static int __init _init_litmus(void)
 {
         /*      Common initializers,
@@ -691,6 +720,8 @@ static int __init _init_litmus(void)
         init_topology();
 #endif
 
+        litmus_enable_perfcounters();
+
         return 0;
 }