On 05/17/2013 11:24 AM, Zoran Markovic wrote:
Since commit <31ade30692dc9680bfc95700d794818fa3f754ac>, timekeeping_init()
checks for presence of persistent clock by attempting to read a non-zero
time value from real-time clock. This is an issue on platforms where
persistent_clock (instead of a RTC) is implemented as a free-running counter
starting from zero on each boot and running during suspend. Examples are some
ARM platforms (e.g. PandaBoard). An attempt to read such a clock during
timekeeping_init() may return zero value and falsely declare persistent clock
as missing. Additionally, in the above case suspend times may be accounted
twice (once from timekeeping_resume() and once from rtc_resume()), resulting
in a gradual drift of system time.
This patch does a run-time correction of the issue by doing the same check
during timekeeping_suspend().
A better long-term solution would have to return error when trying to read
non-existing clock and zero when trying to read an uninitialized clock, but
that would require changing all persistent_clock implementations.
This patch addresses the immediate breakage, for now.
Cc: John Stultz <john.stu...@linaro.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Feng Tang <feng.t...@intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Zoran Markovic <zoran.marko...@linaro.org>
Thanks for finding and sending this out! I'll queue this for 3.10.
thanks again
-john
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