From 1d1bb12a8b1805ddeef9793ebeb920179fb0fa38 Mon Sep 17 00:00:00 2001 From: Cassio Neri Date: Thu, 24 Jun 2021 21:13:43 +0100 Subject: rtc: Improve performance of rtc_time64_to_tm(). Add tests. 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 Reported-by: kernel test robot Signed-off-by: Alexandre Belloni Link: https://lore.kernel.org/r/20210624201343.85441-1-cassio.neri@gmail.com --- drivers/rtc/Makefile | 1 + 1 file changed, 1 insertion(+) (limited to 'drivers/rtc/Makefile') diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile index 2dd0dd956b0e..763d3628c603 100644 --- a/drivers/rtc/Makefile +++ b/drivers/rtc/Makefile @@ -178,3 +178,4 @@ obj-$(CONFIG_RTC_DRV_WM8350) += rtc-wm8350.o obj-$(CONFIG_RTC_DRV_X1205) += rtc-x1205.o obj-$(CONFIG_RTC_DRV_XGENE) += rtc-xgene.o obj-$(CONFIG_RTC_DRV_ZYNQMP) += rtc-zynqmp.o +obj-$(CONFIG_RTC_LIB_KUNIT_TEST) += lib_test.o -- cgit v1.2.3