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Subject[PATCH 2.5] cpufreq: x86 per-CPU loops_per_jiffy notifier
The per-CPU loops_per_jiffy value should be adjusted on frequency transitions.
To get rid of accumulating rounding errors, some reference values are
stored.

Dominik

diff -ruN linux-original/arch/i386/kernel/cpu/common.c linux/arch/i386/kernel/cpu/common.c
--- linux-original/arch/i386/kernel/cpu/common.c 2002-12-21 14:53:44.000000000 +0100
+++ linux/arch/i386/kernel/cpu/common.c 2002-12-21 18:34:34.000000000 +0100
@@ -1,5 +1,7 @@
#include <linux/init.h>
#include <linux/string.h>
+#include <linux/cpufreq.h>
+#include <linux/notifier.h>
#include <linux/delay.h>
#include <linux/smp.h>
#include <asm/semaphore.h>
@@ -61,6 +63,41 @@
#endif
__setup("notsc", tsc_setup);

+#ifdef CONFIG_CPU_FREQ
+static unsigned long loops_per_jiffy_ref = 0;
+static unsigned int ref_freq = 0;
+
+static int
+loops_per_jiffy_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
+ void *data)
+{
+ struct cpufreq_freqs *freq = data;
+
+ if (!loops_per_jiffy_ref) {
+ loops_per_jiffy_ref = cpu_data[freq->cpu].loops_per_jiffy;
+ ref_freq = freq->old;
+ }
+
+ switch (val) {
+ case CPUFREQ_PRECHANGE:
+ if (freq->old < freq->new)
+ cpu_data[freq->cpu].loops_per_jiffy = cpufreq_scale(loops_per_jiffy_ref, ref_freq, freq->new);
+ break;
+ case CPUFREQ_POSTCHANGE:
+ if (freq->new < freq->old)
+ cpu_data[freq->cpu].loops_per_jiffy = cpufreq_scale(loops_per_jiffy_ref, ref_freq, freq->new);
+ break;
+ }
+
+ return 0;
+}
+
+static struct notifier_block loops_per_jiffy_cpufreq_notifier_block = {
+ .notifier_call = loops_per_jiffy_cpufreq_notifier
+};
+#endif
+
+
int __init get_model_name(struct cpuinfo_x86 *c)
{
unsigned int *v;
@@ -350,6 +387,9 @@
for ( i = 0 ; i < NCAPINTS ; i++ )
boot_cpu_data.x86_capability[i] &= c->x86_capability[i];
}
+ if (c == &boot_cpu_data) {
+ cpufreq_register_notifier(&loops_per_jiffy_cpufreq_notifier_block, CPUFREQ_TRANSITION_NOTIFIER);
+ }

printk(KERN_DEBUG "CPU: Common caps: %08lx %08lx %08lx %08lx\n",
boot_cpu_data.x86_capability[0],
-
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