linux-stable.git/drivers/rtc/lib_test.c, branch linux-5.4.y Linux kernel stable tree rtc: test: Fix invalid format specifier. 2025-06-27T10:02:58+00:00 David Gow davidgow@google.com 2024-02-21T09:27:18+00:00 b9dc8b84b9e5375cd239b2c56dc2b8c765bbd431 commit 8a904a3caa88118744062e872ae90f37748a8fd8 upstream. 'days' is a s64 (from div_s64), and so should use a %lld specifier. This was found by extending KUnit's assertion macros to use gcc's __printf attribute. Fixes: 1d1bb12a8b18 ("rtc: Improve performance of rtc_time64_to_tm(). Add tests.") Signed-off-by: David Gow <davidgow@google.com> Tested-by: Guenter Roeck <linux@roeck-us.net> Reviewed-by: Justin Stitt <justinstitt@google.com> Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Signed-off-by: Shuah Khan <skhan@linuxfoundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 8a904a3caa88118744062e872ae90f37748a8fd8 upstream.

'days' is a s64 (from div_s64), and so should use a %lld specifier.

This was found by extending KUnit's assertion macros to use gcc's
__printf attribute.

Fixes: 1d1bb12a8b18 ("rtc: Improve performance of rtc_time64_to_tm(). Add tests.")
Signed-off-by: David Gow <davidgow@google.com>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Justin Stitt <justinstitt@google.com>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
rtc: Improve performance of rtc_time64_to_tm(). Add tests. 2025-06-27T10:02:58+00:00 Cassio Neri cassio.neri@gmail.com 2021-06-24T20:13:43+00:00 31d87dda792b819daf028488dcb4dd3206c2a9cd commit 1d1bb12a8b1805ddeef9793ebeb920179fb0fa38 upstream. The current implementation of rtc_time64_to_tm() contains unnecessary loops, branches and look-up tables. The new one uses an arithmetic-based algorithm appeared in [1] and is approximately 4.3 times faster (YMMV). The drawback is that the new code isn't intuitive and contains many 'magic numbers' (not unusual for this type of algorithm). However, [1] justifies all those numbers and, given this function's history, the code is unlikely to need much maintenance, if any at all. Add a KUnit test case that checks every day in a 160,000 years interval starting on 1970-01-01 against the expected result. Add a new config RTC_LIB_KUNIT_TEST symbol to give the option to run this test suite. [1] Neri, Schneider, "Euclidean Affine Functions and Applications to Calendar Algorithms". https://arxiv.org/abs/2102.06959 Signed-off-by: Cassio Neri <cassio.neri@gmail.com> Reported-by: kernel test robot <lkp@intel.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210624201343.85441-1-cassio.neri@gmail.com Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 1d1bb12a8b1805ddeef9793ebeb920179fb0fa38 upstream.

The current implementation of rtc_time64_to_tm() contains unnecessary
loops, branches and look-up tables. The new one uses an arithmetic-based
algorithm appeared in [1] and is approximately 4.3 times faster (YMMV).

The drawback is that the new code isn't intuitive and contains many 'magic
numbers' (not unusual for this type of algorithm). However, [1] justifies
all those numbers and, given this function's history, the code is unlikely
to need much maintenance, if any at all.

Add a KUnit test case that checks every day in a 160,000 years interval
starting on 1970-01-01 against the expected result. Add a new config
RTC_LIB_KUNIT_TEST symbol to give the option to run this test suite.

[1] Neri, Schneider, "Euclidean Affine Functions and Applications to
Calendar Algorithms". https://arxiv.org/abs/2102.06959

Signed-off-by: Cassio Neri <cassio.neri@gmail.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20210624201343.85441-1-cassio.neri@gmail.com
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>