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latency must be in _nano_seconds

PATCH In review Dominik Brodowski 2 participants 3 messages Nov 19, 2003 – Nov 20, 2003

Subsystems (3)
Arm (32-bit) Arm sub-architectures CPU frequency scaling framework
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Dominik Brodowski

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#0 lore raw

PATCH 7/8 latency must be in _nano_seconds

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 |    2 +-
 arch/i386/kernel/cpu/cpufreq/powernow-k8.c |    4 ++--
 include/linux/cpufreq.h                    |    2 +-
 6 files changed, 8 insertions(+), 8 deletions(-)
arch/arm/mach-integrator/cpu.c +1 -1
diff -ruN linux-original/arch/arm/mach-integrator/cpu.c linux/arch/arm/mach-integrator/cpu.c
@@ -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 */
arch/i386/kernel/cpu/cpufreq/acpi.c +2 -2
diff -ruN linux-original/arch/i386/kernel/cpu/cpufreq/acpi.c linux/arch/i386/kernel/cpu/cpufreq/acpi.c
@@ -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;
arch/i386/kernel/cpu/cpufreq/p4-clockmod.c +1 -1
diff -ruN linux-original/arch/i386/kernel/cpu/cpufreq/p4-clockmod.c linux/arch/i386/kernel/cpu/cpufreq/p4-clockmod.c
@@ -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]);
arch/i386/kernel/cpu/cpufreq/powernow-k7.c +1 -1
diff -ruN linux-original/arch/i386/kernel/cpu/cpufreq/powernow-k7.c linux/arch/i386/kernel/cpu/cpufreq/powernow-k7.c
@@ -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;
 
 	return cpufreq_frequency_table_cpuinfo(policy, powernow_table);
arch/i386/kernel/cpu/cpufreq/powernow-k8.c +2 -2
diff -ruN linux-original/arch/i386/kernel/cpu/cpufreq/powernow-k8.c linux/arch/i386/kernel/cpu/cpufreq/powernow-k8.c
@@ -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;
 
 	if (query_current_values_with_pending_wait())
 		return -EIO;
include/linux/cpufreq.h +1 -1
diff -ruN linux-original/include/linux/cpufreq.h linux/include/linux/cpufreq.h
@@ -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 {
#1 lore raw

arch/i386/kernel/cpu/cpufreq/powernow-k7.c line 390

Quoted 11 lines · Dominik Brodowski

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

arch/i386/kernel/cpu/cpufreq/powernow-k7.c +1 -1
@@ -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)

arch/i386/kernel/cpu/cpufreq/powernow-k8.c line 963

Quoted 11 lines

diff -ruN linux-original/arch/i386/kernel/cpu/cpufreq/powernow-k8.c linux/arch/i386/kernel/cpu/cpufreq/powernow-k8.c

arch/i386/kernel/cpu/cpufreq/powernow-k8.c +2 -2
@@ -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.

Dave

author
#2 lore raw
Quoted 9 lines · Dave Jones
Quoted 7 lines · Dominik Brodowski

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

arch/i386/kernel/cpu/cpufreq/powernow-k7.c +0 -0
@@ -386,7 +386,7 @@
 				minimum_speed, maximum_speed);
Quoted 9 lines

arch/i386/kernel/cpu/cpufreq/powernow-k7.c line 390

Quoted 4 lines
arch/i386/kernel/cpu/cpufreq/powernow-k7.c +1 -1
 	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.

Quoted 6 lines
Quoted 6 lines

diff -ruN linux-original/arch/i386/kernel/cpu/cpufreq/powernow-k8.c linux/arch/i386/kernel/cpu/cpufreq/powernow-k8.c

arch/i386/kernel/cpu/cpufreq/powernow-k8.c +0 -0
@@ -959,8 +959,8 @@
 	pol->governor = CPUFREQ_DEFAULT_GOVERNOR;
Quoted 7 lines

arch/i386/kernel/cpu/cpufreq/powernow-k8.c line 963

Quoted 5 lines
arch/i386/kernel/cpu/cpufreq/powernow-k8.c +2 -2
 	/* 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(-)
arch/arm/mach-integrator/cpu.c +1 -1
diff -ruN linux-original/arch/arm/mach-integrator/cpu.c linux/arch/arm/mach-integrator/cpu.c
@@ -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 */
arch/i386/kernel/cpu/cpufreq/acpi.c +2 -2
diff -ruN linux-original/arch/i386/kernel/cpu/cpufreq/acpi.c linux/arch/i386/kernel/cpu/cpufreq/acpi.c
@@ -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;
arch/i386/kernel/cpu/cpufreq/p4-clockmod.c +1 -1
diff -ruN linux-original/arch/i386/kernel/cpu/cpufreq/p4-clockmod.c linux/arch/i386/kernel/cpu/cpufreq/p4-clockmod.c
@@ -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]);
arch/i386/kernel/cpu/cpufreq/powernow-k7.c +5 -1
diff -ruN linux-original/arch/i386/kernel/cpu/cpufreq/powernow-k7.c linux/arch/i386/kernel/cpu/cpufreq/powernow-k7.c
@@ -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);
arch/i386/kernel/cpu/cpufreq/powernow-k8.c +4 -3
diff -ruN linux-original/arch/i386/kernel/cpu/cpufreq/powernow-k8.c linux/arch/i386/kernel/cpu/cpufreq/powernow-k8.c
@@ -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;
include/linux/cpufreq.h +1 -1
diff -ruN linux-original/include/linux/cpufreq.h linux/include/linux/cpufreq.h
@@ -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 {