[CPUFREQ] Measure transition latency at driver initialization

The attached patch introduces runtime latency measurement for ICH[234]
based chipsets instead of using CPUFREQ_ETERNAL. It includes
some sanity checks in case the measured value is out of range and
assigns a safe value of 500uSec that should still be enough on
problematics chipsets (current testing report values ~200uSec). The
measurement is currently done in speedstep_get_freqs in order to avoid
further unnecessary transitions and in the hope it'll come handy for SMI
also.

Signed-off-by: Mattia Dongili <malattia@linux.it>
Acked-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Dave Jones <davej@redhat.com>

 speedstep-ich.c |    4 ++--
 speedstep-lib.c |   32 +++++++++++++++++++++++++++++++-
 speedstep-lib.h |    1 +
 speedstep-smi.c |    1 +
 4 files changed, 35 insertions(+), 3 deletions(-)

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/i386/kernel/cpu/cpufreq/speedstep-ich.c b/arch/i386/kernel/cpu/cpufreq/speedstep-ich.c
index 5b7d18a06afa..862e0b5656b9 100644
--- a/arch/i386/kernel/cpu/cpufreq/speedstep-ich.c
+++ b/arch/i386/kernel/cpu/cpufreq/speedstep-ich.c
@@ -315,10 +315,11 @@ static int speedstep_cpu_init(struct cpufreq_policy *policy)
         cpus_allowed = current->cpus_allowed;
         set_cpus_allowed(current, policy->cpus);
 
-        /* detect low and high frequency */
+        /* detect low and high frequency and transition latency */
         result = speedstep_get_freqs(speedstep_processor,
                                      &speedstep_freqs[SPEEDSTEP_LOW].frequency,
                                      &speedstep_freqs[SPEEDSTEP_HIGH].frequency,
+                                     &policy->cpuinfo.transition_latency,
                                      &speedstep_set_state);
         set_cpus_allowed(current, cpus_allowed);
         if (result)
@@ -335,7 +336,6 @@ static int speedstep_cpu_init(struct cpufreq_policy *policy)
 
         /* cpuinfo and default policy values */
         policy->governor = CPUFREQ_DEFAULT_GOVERNOR;
-        policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
         policy->cur = speed;
 
         result = cpufreq_frequency_table_cpuinfo(policy, speedstep_freqs);