tree b4bc0e272f6040a3be0fe259bfe45fb51e57515c
parent d1db0eea852497762cab43b905b879dfcd3b8987
author Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> 1398711249 +0530
committer Rafael J. Wysocki <rafael.j.wysocki@intel.com> 1398727372 +0200

cpufreq: longhaul: Fix double invocation of cpufreq_freq_transition_begin/end

During frequency transitions, the cpufreq core takes the responsibility of
invoking cpufreq_freq_transition_begin() and cpufreq_freq_transition_end()
for those cpufreq drivers that define the ->target_index callback but don't
set the ASYNC_NOTIFICATION flag.

The longhaul cpufreq driver falls under this category, but this driver was
invoking the _begin() and _end() APIs itself around frequency transitions,
which led to double invocation of the _begin() API. The _begin API makes
contending callers wait until the previous invocation is complete. Hence,
the longhaul driver ended up waiting on itself, leading to system hangs
during boot.

Fix this by removing the calls to the _begin() and _end() APIs from the
longhaul driver, since they rightly belong to the cpufreq core.

(Note that during module_exit(), the longhaul driver sets the frequency
 without any help from the cpufreq core. So add explicit calls to the
 _begin() and _end() APIs around that frequency transition alone, to take
 care of that special case.)

Fixes: 12478cf0c55e (cpufreq: Make sure frequency transitions are serialized)
Reported-and-tested-by: Meelis Roos <mroos@linux.ee>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>