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authorFeng Tang <feng.tang@intel.com>2013-03-12 07:56:48 +0400
committerJohn Stultz <john.stultz@linaro.org>2013-03-16 03:51:29 +0400
commite445cf1c4257cc0238d72e4129eb4739f46fd3de (patch)
tree5ff9c120a867939996d83dae6e885e81177c1819 /include/linux/timekeeper_internal.h
parent82f9c080b22a5b859ae2b50822dfb6b812898fdb (diff)
downloadlinux-e445cf1c4257cc0238d72e4129eb4739f46fd3de.tar.xz
timekeeping: utilize the suspend-nonstop clocksource to count suspended time
There are some new processors whose TSC clocksource won't stop during suspend. Currently, after system resumes, kernel will use persistent clock or RTC to compensate the sleep time, but with these nonstop clocksources, we could skip the special compensation from external sources, and just use current clocksource for time recounting. This can solve some time drift bugs caused by some not-so-accurate or error-prone RTC devices. The current way to count suspended time is first try to use the persistent clock, and then try the RTC if persistent clock can't be used. This patch will change the trying order to: suspend-nonstop clocksource -> persistent clock -> RTC When counting the sleep time with nonstop clocksource, use an accurate way suggested by Jason Gunthorpe to cover very large delta cycles. Signed-off-by: Feng Tang <feng.tang@intel.com> [jstultz: Small optimization, avoiding re-reading the clocksource] Signed-off-by: John Stultz <john.stultz@linaro.org>
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