dm: rtc: Try to handle the localtime() race

At present the sandbox timer uses localtime() which can jump around twice
a year when daylight-saving time changes.

It would be tricky to make use of gmtime() since we still need to present
the time in local time, as seems to be required by U-Boot's RTC interface.

The problem can only happen once, so use a loop to detect it and try
again. This should be sufficient to detect either a change in the 'second'
value, or a daylight-saving change. We can assume that the latter also
incorporates a 'second' change, so there is no need to loop more than
twice.

Signed-off-by: Simon Glass <sjg@chromium.org>

diff --git a/test/dm/rtc.c b/test/dm/rtc.c
index 50086ff..bf97dbb 100644 (file)
--- a/test/dm/rtc.c
+++ b/test/dm/rtc.c
@@ -252,6 +252,7 @@ static int dm_test_rtc_reset(struct unit_test_state *uts)
        struct rtc_time now;
        struct udevice *dev, *emul;
        long old_base_time, base_time;
+       int i;
 
        ut_assertok(uclass_get_device(UCLASS_RTC, 0, &dev));
        ut_assertok(dm_rtc_get(dev, &now));
@@ -259,19 +260,24 @@ static int dm_test_rtc_reset(struct unit_test_state *uts)
        ut_assertok(i2c_emul_find(dev, &emul));
        ut_assertnonnull(emul);
 
-       old_base_time = sandbox_i2c_rtc_get_set_base_time(emul, 0);
-
-       ut_asserteq(0, sandbox_i2c_rtc_get_set_base_time(emul, -1));
-
-       /*
-        * Resetting the RTC should put the base time back to normal. Allow for
-        * a one-second adjustment in case the time flips over while this
-        * test process is pre-empted, since reset_time() in i2c_rtc_emul.c
-        * reads the time from the OS.
-        */
-       ut_assertok(dm_rtc_reset(dev));
-       base_time = sandbox_i2c_rtc_get_set_base_time(emul, -1);
-       ut_assert(base_time - old_base_time <= 1);
+       i = 0;
+       do {
+               old_base_time = sandbox_i2c_rtc_get_set_base_time(emul, 0);
+
+               ut_asserteq(0, sandbox_i2c_rtc_get_set_base_time(emul, -1));
+
+               ut_assertok(dm_rtc_reset(dev));
+               base_time = sandbox_i2c_rtc_get_set_base_time(emul, -1);
+
+               /*
+                * Resetting the RTC should put the base time back to normal.
+                * Allow for a one-timeadjustment in case the time flips over
+                * while this test process is pre-empted (either by a second
+                * or a daylight-saving change), since reset_time() in
+                * i2c_rtc_emul.c reads the time from the OS.
+                */
+       } while (++i < 2 && base_time != old_base_time);
+       ut_asserteq(old_base_time, base_time);
 
        return 0;
 }