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[CPUFREQ] Measure transition latency at driver initialization

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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(-)
This commit is contained in:
Mattia Dongili 2005-12-02 21:59:41 +01:00 committed by Dave Jones
parent fc457fa7c0
commit 1a10760c91
4 changed files with 35 additions and 3 deletions
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4
arch/i386/kernel/cpu/cpufreq/speedstep-ich.c
View File

@ -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);

32
arch/i386/kernel/cpu/cpufreq/speedstep-lib.c
View File

@ -320,11 +320,13 @@ EXPORT_SYMBOL_GPL(speedstep_detect_processor);
unsigned int speedstep_get_freqs(unsigned int processor,
unsigned int *low_speed,
unsigned int *high_speed,
unsigned int *transition_latency,
void (*set_state) (unsigned int state))
{
unsigned int prev_speed;
unsigned int ret = 0;
unsigned long flags;
struct timeval tv1, tv2;
if ((!processor) || (!low_speed) || (!high_speed) || (!set_state))
return -EINVAL;
@ -337,7 +339,7 @@ unsigned int speedstep_get_freqs(unsigned int processor,
return -EIO;
dprintk("previous speed is %u\n", prev_speed);
local_irq_save(flags);
/* switch to low state */
@ -350,8 +352,17 @@ unsigned int speedstep_get_freqs(unsigned int processor,
dprintk("low speed is %u\n", *low_speed);
/* start latency measurement */
if (transition_latency)
do_gettimeofday(&tv1);
/* switch to high state */
set_state(SPEEDSTEP_HIGH);
/* end latency measurement */
if (transition_latency)
do_gettimeofday(&tv2);
*high_speed = speedstep_get_processor_frequency(processor);
if (!*high_speed) {
ret = -EIO;
@ -369,6 +380,25 @@ unsigned int speedstep_get_freqs(unsigned int processor,
if (*high_speed != prev_speed)
set_state(SPEEDSTEP_LOW);
if (transition_latency) {
*transition_latency = (tv2.tv_sec - tv1.tv_sec) * USEC_PER_SEC +
tv2.tv_usec - tv1.tv_usec;
dprintk("transition latency is %u uSec\n", *transition_latency);
/* convert uSec to nSec and add 20% for safety reasons */
*transition_latency *= 1200;
/* check if the latency measurement is too high or too low
* and set it to a safe value (500uSec) in that case
*/
if (*transition_latency > 10000000 || *transition_latency < 50000) {
printk (KERN_WARNING "speedstep: frequency transition measured seems out of "
"range (%u nSec), falling back to a safe one of %u nSec.\n",
*transition_latency, 500000);
*transition_latency = 500000;
}
}
out:
local_irq_restore(flags);
return (ret);

1
arch/i386/kernel/cpu/cpufreq/speedstep-lib.h
View File

@ -44,4 +44,5 @@ extern unsigned int speedstep_get_processor_frequency(unsigned int processor);
extern unsigned int speedstep_get_freqs(unsigned int processor,
unsigned int *low_speed,
unsigned int *high_speed,
unsigned int *transition_latency,
void (*set_state) (unsigned int state));

1
arch/i386/kernel/cpu/cpufreq/speedstep-smi.c
View File

@ -269,6 +269,7 @@ static int speedstep_cpu_init(struct cpufreq_policy *policy)
result = speedstep_get_freqs(speedstep_processor,
&speedstep_freqs[SPEEDSTEP_LOW].frequency,
&speedstep_freqs[SPEEDSTEP_HIGH].frequency,
NULL,
&speedstep_set_state);
if (result) {