• Srivatsa S. Bhat's avatar
    cpufreq: longhaul: Fix double invocation of cpufreq_freq_transition_begin/end · 7aa0557f
    Srivatsa S. Bhat authored
    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: 12478cf0 (cpufreq: Make sure frequency transitions are serialized)
    Reported-and-tested-by: default avatarMeelis Roos <mroos@linux.ee>
    Signed-off-by: default avatarSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
    Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
    7aa0557f
longhaul.c 25.8 KB