]> git.baikalelectronics.ru Git - kernel.git/commit
cpufreq: send new set of notification for transition failures
authorViresh Kumar <viresh.kumar@linaro.org>
Mon, 2 Dec 2013 05:34:13 +0000 (11:04 +0530)
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>
Mon, 6 Jan 2014 00:43:44 +0000 (01:43 +0100)
commit42d3d9afb9535c3b7dbc5c857216da6be7fcc78b
treeb592025459590a4564fd8e7760707c7d77a159e1
parent02f7e3f2422fd6cf9355fda7d16d01b8baed4230
cpufreq: send new set of notification for transition failures

In the current code, if we fail during a frequency transition, we
simply send the POSTCHANGE notification with the old frequency. This
isn't enough.

One of the core users of these notifications is the code responsible
for keeping loops_per_jiffy aligned with frequency changes. And mostly
it is written as:

if ((val == CPUFREQ_PRECHANGE  && freq->old < freq->new) ||
    (val == CPUFREQ_POSTCHANGE && freq->old > freq->new)) {
update-loops-per-jiffy...
}

So, suppose we are changing to a higher frequency and failed during
transition, then following will happen:
- CPUFREQ_PRECHANGE notification with freq-new > freq-old
- CPUFREQ_POSTCHANGE notification with freq-new == freq-old

The first one will update loops_per_jiffy and second one will do
nothing. Even if we send the 2nd notification by exchanging values of
freq-new and old, some users of these notifications might get
unstable.

This can be fixed by simply calling cpufreq_notify_post_transition()
with error code and this routine will take care of sending
notifications in the correct order.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
[rjw: Folded 3 patches into one, rebased unicore2 changes]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
drivers/cpufreq/cpufreq.c
drivers/cpufreq/pcc-cpufreq.c
drivers/cpufreq/powernow-k8.c
drivers/cpufreq/unicore2-cpufreq.c