From: Dominik Brodowski <linux@brodo.de>
To: Dave Jones <davej@redhat.com>
Cc: cpufreq@www.linux.org.uk
Subject: Re: [PATCH 7/8] latency must be in _nano_seconds
Date: Thu, 20 Nov 2003 19:31:33 +0100 [thread overview]
Message-ID: <20031120183133.GA4425@brodo.de> (raw)
In-Reply-To: <20031119190725.GA5653@redhat.com>
On Wed, Nov 19, 2003 at 07:07:25PM +0000, Dave Jones wrote:
> On Wed, Nov 19, 2003 at 07:33:30PM +0100, Dominik Brodowski wrote:
>
> > return cpufreq_frequency_table_cpuinfo(policy, &p4clockmod_table[0]);
> > diff -ruN linux-original/arch/i386/kernel/cpu/cpufreq/powernow-k7.c linux/arch/i386/kernel/cpu/cpufreq/powernow-k7.c
> > --- linux-original/arch/i386/kernel/cpu/cpufreq/powernow-k7.c 2003-11-19 17:06:10.571868800 +0100
> > +++ linux/arch/i386/kernel/cpu/cpufreq/powernow-k7.c 2003-11-19 18:48:10.150551432 +0100
> > @@ -386,7 +386,7 @@
> > minimum_speed, maximum_speed);
> >
> > policy->governor = CPUFREQ_DEFAULT_GOVERNOR;
> > - policy->cpuinfo.transition_latency = latency;
> > + policy->cpuinfo.transition_latency = latency * 20;
> > policy->cur = maximum_speed;
>
> Can we at least get a comment explaining where '20' comes from
> when we add magic numbers like this? I know, and you know, but
> it's a little non-obvious, and in six months time, I'll probably
> have forgotten too 8)
Comment added.
> > diff -ruN linux-original/arch/i386/kernel/cpu/cpufreq/powernow-k8.c linux/arch/i386/kernel/cpu/cpufreq/powernow-k8.c
> > --- linux-original/arch/i386/kernel/cpu/cpufreq/powernow-k8.c 2003-11-19 17:07:58.537455536 +0100
> > +++ linux/arch/i386/kernel/cpu/cpufreq/powernow-k8.c 2003-11-19 18:46:57.031667192 +0100
> > @@ -959,8 +959,8 @@
> > pol->governor = CPUFREQ_DEFAULT_GOVERNOR;
> >
> > /* Take a crude guess here. */
> > - pol->cpuinfo.transition_latency = ((rvo + 8) * vstable * VST_UNITS_20US)
> > - + (3 * (1 << irt) * 10);
> > + pol->cpuinfo.transition_latency = (((rvo + 8) * vstable * VST_UNITS_20US)
> > + + (3 * (1 << irt) * 10)) * 1000;
>
> Ditto. This one moreso, as its quite complex to begin with.
What Paul Devriendt did here I do not know, but I added a comment for the
factor "1000"...
Dominik
Even though the core stated that cpuinfo.transition_latency needs to be
in 10^(-9) s, hardly any driver set it to nanoseconds but to microseconds.
So, fix up the drivers.
arch/arm/mach-integrator/cpu.c | 2 +-
arch/i386/kernel/cpu/cpufreq/acpi.c | 4 ++--
arch/i386/kernel/cpu/cpufreq/p4-clockmod.c | 2 +-
arch/i386/kernel/cpu/cpufreq/powernow-k7.c | 6 +++++-
arch/i386/kernel/cpu/cpufreq/powernow-k8.c | 7 ++++---
include/linux/cpufreq.h | 2 +-
6 files changed, 14 insertions(+), 9 deletions(-)
diff -ruN linux-original/arch/arm/mach-integrator/cpu.c linux/arch/arm/mach-integrator/cpu.c
--- linux-original/arch/arm/mach-integrator/cpu.c 2003-11-20 19:17:28.489660360 +0100
+++ linux/arch/arm/mach-integrator/cpu.c 2003-11-20 19:17:34.311775264 +0100
@@ -172,7 +172,7 @@
policy->governor = CPUFREQ_DEFAULT_GOVERNOR;
policy->cpuinfo.max_freq = 160000;
policy->cpuinfo.min_freq = 12000;
- policy->cpuinfo.transition_latency = 1000; /* 1 ms, assumed */
+ policy->cpuinfo.transition_latency = 1000000; /* 1 ms, assumed */
policy->cur = policy->min = policy->max =
icst525_khz(&cclk_params, vco); /* current freq */
diff -ruN linux-original/arch/i386/kernel/cpu/cpufreq/acpi.c linux/arch/i386/kernel/cpu/cpufreq/acpi.c
--- linux-original/arch/i386/kernel/cpu/cpufreq/acpi.c 2003-11-20 19:17:28.510657168 +0100
+++ linux/arch/i386/kernel/cpu/cpufreq/acpi.c 2003-11-20 19:17:34.312775112 +0100
@@ -578,8 +578,8 @@
/* detect transition latency */
policy->cpuinfo.transition_latency = 0;
for (i=0;i<perf->state_count;i++) {
- if (perf->states[i].transition_latency > policy->cpuinfo.transition_latency)
- policy->cpuinfo.transition_latency = perf->states[i].transition_latency;
+ if ((perf->states[i].transition_latency * 1000) > policy->cpuinfo.transition_latency)
+ policy->cpuinfo.transition_latency = perf->states[i].transition_latency * 1000;
}
policy->governor = CPUFREQ_DEFAULT_GOVERNOR;
policy->cur = perf->states[pr->limit.state.px].core_frequency * 1000;
diff -ruN linux-original/arch/i386/kernel/cpu/cpufreq/p4-clockmod.c linux/arch/i386/kernel/cpu/cpufreq/p4-clockmod.c
--- linux-original/arch/i386/kernel/cpu/cpufreq/p4-clockmod.c 2003-11-20 19:17:28.540652608 +0100
+++ linux/arch/i386/kernel/cpu/cpufreq/p4-clockmod.c 2003-11-20 19:17:34.312775112 +0100
@@ -255,7 +255,7 @@
/* cpuinfo and default policy values */
policy->governor = CPUFREQ_DEFAULT_GOVERNOR;
- policy->cpuinfo.transition_latency = 1000;
+ policy->cpuinfo.transition_latency = 1000000; /* assumed */
policy->cur = stock_freq;
return cpufreq_frequency_table_cpuinfo(policy, &p4clockmod_table[0]);
diff -ruN linux-original/arch/i386/kernel/cpu/cpufreq/powernow-k7.c linux/arch/i386/kernel/cpu/cpufreq/powernow-k7.c
--- linux-original/arch/i386/kernel/cpu/cpufreq/powernow-k7.c 2003-11-20 19:17:28.541652456 +0100
+++ linux/arch/i386/kernel/cpu/cpufreq/powernow-k7.c 2003-11-20 19:20:35.230271472 +0100
@@ -386,7 +386,11 @@
minimum_speed, maximum_speed);
policy->governor = CPUFREQ_DEFAULT_GOVERNOR;
- policy->cpuinfo.transition_latency = latency;
+
+ /* latency is in 10 ns (look for SGTC above) for each VID
+ * and FID transition, so multiply that value with 20 */
+ policy->cpuinfo.transition_latency = latency * 20;
+
policy->cur = maximum_speed;
return cpufreq_frequency_table_cpuinfo(policy, powernow_table);
diff -ruN linux-original/arch/i386/kernel/cpu/cpufreq/powernow-k8.c linux/arch/i386/kernel/cpu/cpufreq/powernow-k8.c
--- linux-original/arch/i386/kernel/cpu/cpufreq/powernow-k8.c 2003-11-20 19:17:28.591644856 +0100
+++ linux/arch/i386/kernel/cpu/cpufreq/powernow-k8.c 2003-11-20 19:18:45.550945264 +0100
@@ -958,9 +958,10 @@
pol->governor = CPUFREQ_DEFAULT_GOVERNOR;
- /* Take a crude guess here. */
- pol->cpuinfo.transition_latency = ((rvo + 8) * vstable * VST_UNITS_20US)
- + (3 * (1 << irt) * 10);
+ /* Take a crude guess here.
+ * That guess was in microseconds, so multply with 1000 */
+ pol->cpuinfo.transition_latency = (((rvo + 8) * vstable * VST_UNITS_20US)
+ + (3 * (1 << irt) * 10)) * 1000;
if (query_current_values_with_pending_wait())
return -EIO;
diff -ruN linux-original/include/linux/cpufreq.h linux/include/linux/cpufreq.h
--- linux-original/include/linux/cpufreq.h 2003-11-20 19:17:28.695629048 +0100
+++ linux/include/linux/cpufreq.h 2003-11-20 19:17:34.314774808 +0100
@@ -57,7 +57,7 @@
struct cpufreq_cpuinfo {
unsigned int max_freq;
unsigned int min_freq;
- unsigned int transition_latency; /* in 10^(-9) s */
+ unsigned int transition_latency; /* in 10^(-9) s = nanoseconds */
};
struct cpufreq_real_policy {
prev parent reply other threads:[~2003-11-20 18:31 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-11-19 18:33 [PATCH 7/8] latency must be in _nano_seconds Dominik Brodowski
2003-11-19 19:07 ` Dave Jones
2003-11-20 18:31 ` Dominik Brodowski [this message]
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