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/lib_test.c | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 79 insertions(+) create mode 100644 drivers/rtc/lib_test.c (limited to 'drivers/rtc/lib_test.c') diff --git a/drivers/rtc/lib_test.c b/drivers/rtc/lib_test.c new file mode 100644 index 000000000000..2124b67a2f43 --- /dev/null +++ b/drivers/rtc/lib_test.c @@ -0,0 +1,79 @@ +// SPDX-License-Identifier: LGPL-2.1+ + +#include +#include + +/* + * Advance a date by one day. + */ +static void advance_date(int *year, int *month, int *mday, int *yday) +{ + if (*mday != rtc_month_days(*month - 1, *year)) { + ++*mday; + ++*yday; + return; + } + + *mday = 1; + if (*month != 12) { + ++*month; + ++*yday; + return; + } + + *month = 1; + *yday = 1; + ++*year; +} + +/* + * Checks every day in a 160000 years interval starting on 1970-01-01 + * against the expected result. + */ +static void rtc_time64_to_tm_test_date_range(struct kunit *test) +{ + /* + * 160000 years = (160000 / 400) * 400 years + * = (160000 / 400) * 146097 days + * = (160000 / 400) * 146097 * 86400 seconds + */ + time64_t total_secs = ((time64_t) 160000) / 400 * 146097 * 86400; + + int year = 1970; + int month = 1; + int mday = 1; + int yday = 1; + + struct rtc_time result; + time64_t secs; + s64 days; + + for (secs = 0; secs <= total_secs; secs += 86400) { + + rtc_time64_to_tm(secs, &result); + + days = div_s64(secs, 86400); + + #define FAIL_MSG "%d/%02d/%02d (%2d) : %ld", \ + year, month, mday, yday, days + + KUNIT_ASSERT_EQ_MSG(test, year - 1900, result.tm_year, FAIL_MSG); + KUNIT_ASSERT_EQ_MSG(test, month - 1, result.tm_mon, FAIL_MSG); + KUNIT_ASSERT_EQ_MSG(test, mday, result.tm_mday, FAIL_MSG); + KUNIT_ASSERT_EQ_MSG(test, yday, result.tm_yday, FAIL_MSG); + + advance_date(&year, &month, &mday, &yday); + } +} + +static struct kunit_case rtc_lib_test_cases[] = { + KUNIT_CASE(rtc_time64_to_tm_test_date_range), + {} +}; + +static struct kunit_suite rtc_lib_test_suite = { + .name = "rtc_lib_test_cases", + .test_cases = rtc_lib_test_cases, +}; + +kunit_test_suite(rtc_lib_test_suite); -- cgit From 5546e3dfb65a4389e747766ac455a50c3675fb0f Mon Sep 17 00:00:00 2001 From: Alexandre Belloni Date: Tue, 10 Aug 2021 23:20:06 +0200 Subject: rtc: lib_test: add MODULE_LICENSE 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 Signed-off-by: Alexandre Belloni Link: https://lore.kernel.org/r/20210810212008.631359-1-alexandre.belloni@bootlin.com --- drivers/rtc/lib_test.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'drivers/rtc/lib_test.c') diff --git a/drivers/rtc/lib_test.c b/drivers/rtc/lib_test.c index 2124b67a2f43..d5caf36c56cd 100644 --- a/drivers/rtc/lib_test.c +++ b/drivers/rtc/lib_test.c @@ -77,3 +77,5 @@ static struct kunit_suite rtc_lib_test_suite = { }; kunit_test_suite(rtc_lib_test_suite); + +MODULE_LICENSE("GPL"); -- cgit