GitHub-Mirror/linux-bl808
2
0
Fork 0
mirror of https://github.com/Fishwaldo/linux-bl808.git synced 2025-06-17 20:25:19 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions

rtc: Improve performance of rtc_time64_to_tm(). Add tests.

Browse source 
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
This commit is contained in:
Cassio Neri 2021-06-24 21:13:43 +01:00 • committed by Alexandre Belloni
parent fffd603ae9
commit 1d1bb12a8b
4 changed files with 168 additions and 25 deletions
Download patch file Download diff file Expand all files Collapse all files

79
drivers/rtc/lib_test.c Normal file
View file

@ -0,0 +1,79 @@
// SPDX-License-Identifier: LGPL-2.1+
#include <kunit/test.h>
#include <linux/rtc.h>
/*
* 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);