clocksource: exynos_mct: Fix ftrace

In (93bfb76 clocksource: exynos_mct: register sched_clock callback) we
supported using the MCT as a scheduler clock.  We properly marked
exynos4_read_sched_clock() as notrace.  However, we then went and
called another function that _wasn't_ notrace.  That means if you do:

  cd /sys/kernel/debug/tracing/
  echo function_graph > current_tracer

You'll get a crash.

Fix this (but still let other readers of the MCT be trace-enabled) by
adding an extra function.  It's important to keep other users of MCT
traceable because the MCT is actually quite slow to access and we want
exynos4_frc_read() to show up in ftrace profiles if it's the
bottleneck.

Signed-off-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c
index f71d55f5e6e5..5ce99c07ce8c 100644
--- a/drivers/clocksource/exynos_mct.c
+++ b/drivers/clocksource/exynos_mct.c
@@ -162,7 +162,7 @@ static void exynos4_mct_frc_start(void)
         exynos4_mct_write(reg, EXYNOS4_MCT_G_TCON);
 }
 
-static cycle_t exynos4_frc_read(struct clocksource *cs)
+static cycle_t notrace _exynos4_frc_read(void)
 {
         unsigned int lo, hi;
         u32 hi2 = __raw_readl(reg_base + EXYNOS4_MCT_G_CNT_U);
@@ -176,6 +176,11 @@ static cycle_t exynos4_frc_read(struct clocksource *cs)
         return ((cycle_t)hi << 32) | lo;
 }
 
+static cycle_t exynos4_frc_read(struct clocksource *cs)
+{
+        return _exynos4_frc_read();
+}
+
 static void exynos4_frc_resume(struct clocksource *cs)
 {
         exynos4_mct_frc_start();
@@ -192,7 +197,7 @@ struct clocksource mct_frc = {
 
 static u64 notrace exynos4_read_sched_clock(void)
 {
-        return exynos4_frc_read(&mct_frc);
+        return _exynos4_frc_read();
 }
 
 static void __init exynos4_clocksource_init(void)