From: Mattia Dongili Date: Fri, 2 Dec 2005 20:59:41 +0000 (+0100) Subject: [CPUFREQ] Measure transition latency at driver initialization X-Git-Tag: v2.6.16-rc1~474^2~22^2~11^2~2 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1a10760c91c394dfe4adfefeeaf85cd8098c4894;p=linux-2.6 [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 Acked-by: Dominik Brodowski Signed-off-by: Dave Jones speedstep-ich.c | 4 ++-- speedstep-lib.c | 32 +++++++++++++++++++++++++++++++- speedstep-lib.h | 1 + speedstep-smi.c | 1 + 4 files changed, 35 insertions(+), 3 deletions(-) --- diff --git a/arch/i386/kernel/cpu/cpufreq/speedstep-ich.c b/arch/i386/kernel/cpu/cpufreq/speedstep-ich.c index 5b7d18a06a..862e0b5656 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); diff --git a/arch/i386/kernel/cpu/cpufreq/speedstep-lib.c b/arch/i386/kernel/cpu/cpufreq/speedstep-lib.c index d368b3f5fc..7c47005a18 100644 --- a/arch/i386/kernel/cpu/cpufreq/speedstep-lib.c +++ b/arch/i386/kernel/cpu/cpufreq/speedstep-lib.c @@ -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); diff --git a/arch/i386/kernel/cpu/cpufreq/speedstep-lib.h b/arch/i386/kernel/cpu/cpufreq/speedstep-lib.h index 261a2c9b7f..6a727fd3a7 100644 --- a/arch/i386/kernel/cpu/cpufreq/speedstep-lib.h +++ b/arch/i386/kernel/cpu/cpufreq/speedstep-lib.h @@ -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)); diff --git a/arch/i386/kernel/cpu/cpufreq/speedstep-smi.c b/arch/i386/kernel/cpu/cpufreq/speedstep-smi.c index 2718fb6f6a..28cc5d524a 100644 --- a/arch/i386/kernel/cpu/cpufreq/speedstep-smi.c +++ b/arch/i386/kernel/cpu/cpufreq/speedstep-smi.c @@ -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) {