kernel: time: Add udelay_test module to validate udelay

Create a module that allows udelay() to be executed to ensure that
it is delaying at least as long as requested (with a little bit of
error allowed).

There are some configurations which don't have reliably udelay
due to using a loop delay with cpufreq changes which should use
a counter time based delay instead.  This test aims to identify
those configurations where timing is unreliable.

Signed-off-by: David Riley <davidriley@chromium.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/kernel/time/Makefile b/kernel/time/Makefile
index e59ce8b1b550..7347426fa68d 100644
--- a/kernel/time/Makefile
+++ b/kernel/time/Makefile
@@ -13,6 +13,7 @@ obj-$(CONFIG_TICK_ONESHOT)			+= tick-oneshot.o
 obj-$(CONFIG_TICK_ONESHOT)                      += tick-sched.o
 obj-$(CONFIG_TIMER_STATS)                       += timer_stats.o
 obj-$(CONFIG_DEBUG_FS)                          += timekeeping_debug.o
+obj-$(CONFIG_TEST_UDELAY)                       += udelay_test.o
 
 $(obj)/time.o: $(obj)/timeconst.h
 
@@ -29,3 +30,4 @@ quiet_cmd_bc  = BC      $@
 targets += timeconst.h
 $(obj)/timeconst.h: $(obj)/hz.bc $(src)/timeconst.bc FORCE
         $(call if_changed,bc)
+