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2021-08-11rtc: lib_test: add MODULE_LICENSEAlexandre Belloni1-0/+2
As the documentation states, "The exact license information can only be determined via the license information in the corresponding source files." and the SPDX identifier has the proper information. Reported-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210810212008.631359-1-alexandre.belloni@bootlin.com
2021-08-10rtc: Improve performance of rtc_time64_to_tm(). Add tests.Cassio Neri1-0/+79
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