From: Soren Brinkmann <soren.brinkmann@xilinx.com>
Date: Wed, 19 Feb 2014 23:14:42 +0000 (-0800)
Subject: clocksource/cadence_ttc: Overhaul clocksource frequency adjustment
X-Git-Tag: v3.15-rc1~153^2~11
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b3e90722f6f53fa457a88146a877e34ea71d25ea;p=pandora-kernel.git

clocksource/cadence_ttc: Overhaul clocksource frequency adjustment

The currently used method adjusting the clocksource to a changing input
frequency does not work on kernels from 3.11 on.
The new approach is to keep the timer frequency as constant as possible.
I.e.
 - due to the TTC's prescaler limitations, allow frequency changes
   only if the frequency scales by a power of 2
 - adjust the counter's divider on the fly when a frequency change
   occurs

This limits cpufreq to scale by certain factors only.
But we may keep the time base somewhat constant, so that sleep() & co
keep working as expected, while supporting cpufreq.

Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Michal Simek <michal.simek@xilinx.com>
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