summaryrefslogtreecommitdiffstats
path: root/drivers/rtc/rtc-tile.c
diff options
context:
space:
mode:
authorJulius Werner <jwerner@chromium.org>2015-12-15 15:02:49 -0800
committerAlexandre Belloni <alexandre.belloni@free-electrons.com>2015-12-20 13:39:00 +0100
commitf076ef44a44d02ed91543f820c14c2c7dff53716 (patch)
treec688b67340d129d687c44d5ee274ccd412573b9e /drivers/rtc/rtc-tile.c
parent3abb1ada21a4fb5b2920457a2e5c8483abb09a45 (diff)
downloadlinux-f076ef44a44d02ed91543f820c14c2c7dff53716.tar.bz2
rtc: rk808: Compensate for Rockchip calendar deviation on November 31st
In A.D. 1582 Pope Gregory XIII found that the existing Julian calendar insufficiently represented reality, and changed the rules about calculating leap years to account for this. Similarly, in A.D. 2013 Rockchip hardware engineers found that the new Gregorian calendar still contained flaws, and that the month of November should be counted up to 31 days instead. Unfortunately it takes a long time for calendar changes to gain widespread adoption, and just like more than 300 years went by before the last Protestant nation implemented Greg's proposal, we will have to wait a while until all religions and operating system kernels acknowledge the inherent advantages of the Rockchip system. Until then we need to translate dates read from (and written to) Rockchip hardware back to the Gregorian format. This patch works by defining Jan 1st, 2016 as the arbitrary anchor date on which Rockchip and Gregorian calendars are in sync. From that we can translate arbitrary later dates back and forth by counting the number of November/December transitons since the anchor date to determine the offset between the calendars. We choose this method (rather than trying to regularly "correct" the date stored in hardware) since it's the only way to ensure perfect time-keeping even if the system may be shut down for an unknown number of years. The drawback is that other software reading the same hardware (e.g. mainboard firmware) must use the same translation convention (including the same anchor date) to be able to read and write correct timestamps from/to the RTC. Signed-off-by: Julius Werner <jwerner@chromium.org> Reviewed-by: Douglas Anderson <dianders@chromium.org> Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Diffstat (limited to 'drivers/rtc/rtc-tile.c')
0 files changed, 0 insertions, 0 deletions