linux-kernel - [RFC][PATCH 0/2] Avoid accumulating drift in suspend/resume

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Message-Id: <1306908469-15275-1-git-send-email-john.stultz@linaro.org>
Date:	Tue, 31 May 2011 23:07:47 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	linux-kernel@...r.kernel.org
Cc:	John Stultz <john.stultz@...aro.org>,
	Arve Hjønnevåg <arve@...roid.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [RFC][PATCH 0/2] Avoid accumulating drift in suspend/resume

Arve Hjønnevåg noted that in the suspend/resume path, we're likely to see
half-second errors from each read of the RTC. If a system is frequently
suspended, these errors will accumulate quickly.

Arve's solution was to compare the time delta between the system time
and the RTC, for each suspend. If the difference is small, use the same
delta for each suspend. This consistency avoids the error from accumulating.

This patch set implements Arve's suggestion for both the RTC and persistent
clock suspend paths.

Initial tests show that this improves time accuracy over many repeated
suspends. So while testing continues, I just wanted to send this out for
review and feedback.

thanks
-john

CC: Arve Hjønnevåg <arve@...roid.com>
CC: Thomas Gleixner <tglx@...utronix.de>

John Stultz (2):
  time: Avoid accumulating time drift in suspend/resume
  rtc: Avoid accumulating time drift in suspend/resume

 drivers/rtc/class.c       |   65 +++++++++++++++++++++++++++++++++------------
 kernel/time/timekeeping.c |   22 +++++++++++++++
 2 files changed, 70 insertions(+), 17 deletions(-)

-- 
1.7.3.2.146.gca209

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