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Commit 1a10760c authored by Mattia Dongili's avatar Mattia Dongili Committed by Dave Jones
Browse files

[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: default avatarMattia Dongili <malattia@linux.it>
Acked-by: default avatarDominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: default avatarDave 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(-)
parent fc457fa7

arch/i386/kernel/cpu/cpufreq/speedstep-ich.c

+2 −2
Original line number Diff line number Diff line
@@ -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);

arch/i386/kernel/cpu/cpufreq/speedstep-lib.c

+31 −1
Original line number Diff line number Diff line
@@ -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;
@@ -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);

arch/i386/kernel/cpu/cpufreq/speedstep-lib.h

+1 −0
Original line number Diff line number Diff line
@@ -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));

arch/i386/kernel/cpu/cpufreq/speedstep-smi.c

+1 −0
Original line number Diff line number Diff line
@@ -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) {