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Subject[PATCH 2.5.54] cpufreq: update timer notifier
- global loops_per_jiffy, x86 cpu_khz and x86
fast_gettimeoffset_quotient can only be safely adjusted on UP
- x86 per-CPU loops_per_jiffy does not depend on TSC
- save reference values so that rounding errors do not accumulate

arch/i386/kernel/timers/timer_tsc.c | 54 ++++++++++++++++++------------------
kernel/cpufreq.c | 20 ++++++++++---
2 files changed, 42 insertions(+), 32 deletions(-)

diff -ruN linux-original/arch/i386/kernel/timers/timer_tsc.c linux/arch/i386/kernel/timers/timer_tsc.c
--- linux-original/arch/i386/kernel/timers/timer_tsc.c 2003-01-06 12:55:43.000000000 +0100
+++ linux/arch/i386/kernel/timers/timer_tsc.c 2003-01-06 14:20:31.000000000 +0100
@@ -189,39 +189,38 @@


#ifdef CONFIG_CPU_FREQ
+static unsigned int ref_freq = 0;
+static unsigned long loops_per_jiffy_ref = 0;
+
+#ifndef CONFIG_SMP
+static unsigned long fast_gettimeoffset_ref = 0;
+static unsigned long cpu_khz_ref = 0;
+#endif

static int
time_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
void *data)
{
struct cpufreq_freqs *freq = data;
- unsigned int i;

- if (!cpu_has_tsc)
- return 0;
+ if (!ref_freq) {
+ ref_freq = freq->old;
+ loops_per_jiffy_ref = cpu_data[freq->cpu].loops_per_jiffy;
+#ifndef CONFIG_SMP
+ fast_gettimeoffset_ref = fast_gettimeoffset_quotient;
+ cpu_khz_ref = cpu_khz;
+#endif
+ }

- switch (val) {
- case CPUFREQ_PRECHANGE:
- if ((freq->old < freq->new) &&
- ((freq->cpu == CPUFREQ_ALL_CPUS) || (freq->cpu == 0))) {
- cpu_khz = cpufreq_scale(cpu_khz, freq->old, freq->new);
- fast_gettimeoffset_quotient = cpufreq_scale(fast_gettimeoffset_quotient, freq->new, freq->old);
- }
- for (i=0; i<NR_CPUS; i++)
- if ((freq->cpu == CPUFREQ_ALL_CPUS) || (freq->cpu == i))
- cpu_data[i].loops_per_jiffy = cpufreq_scale(cpu_data[i].loops_per_jiffy, freq->old, freq->new);
- break;
-
- case CPUFREQ_POSTCHANGE:
- if ((freq->new < freq->old) &&
- ((freq->cpu == CPUFREQ_ALL_CPUS) || (freq->cpu == 0))) {
- cpu_khz = cpufreq_scale(cpu_khz, freq->old, freq->new);
- fast_gettimeoffset_quotient = cpufreq_scale(fast_gettimeoffset_quotient, freq->new, freq->old);
+ if ((val == CPUFREQ_PRECHANGE && freq->old < freq->new) ||
+ (val == CPUFREQ_POSTCHANGE && freq->old > freq->new)) {
+ cpu_data[freq->cpu].loops_per_jiffy = cpufreq_scale(loops_per_jiffy_ref, ref_freq, freq->new);
+#ifndef CONFIG_SMP
+ if (use_tsc) {
+ fast_gettimeoffset_quotient = cpufreq_scale(fast_gettimeoffset_ref, freq->new, ref_freq);
+ cpu_khz = cpufreq_scale(cpu_khz_ref, ref_freq, freq->new);
}
- for (i=0; i<NR_CPUS; i++)
- if ((freq->cpu == CPUFREQ_ALL_CPUS) || (freq->cpu == i))
- cpu_data[i].loops_per_jiffy = cpufreq_scale(cpu_data[i].loops_per_jiffy, freq->old, freq->new);
- break;
+#endif
}

return 0;
@@ -260,6 +259,10 @@
* moaned if you have the only one in the world - you fix it!
*/

+#ifdef CONFIG_CPU_FREQ
+ cpufreq_register_notifier(&time_cpufreq_notifier_block, CPUFREQ_TRANSITION_NOTIFIER);
+#endif
+
if (cpu_has_tsc) {
unsigned long tsc_quotient = calibrate_tsc();
if (tsc_quotient) {
@@ -282,9 +285,6 @@
"0" (eax), "1" (edx));
printk("Detected %lu.%03lu MHz processor.\n", cpu_khz / 1000, cpu_khz % 1000);
}
-#ifdef CONFIG_CPU_FREQ
- cpufreq_register_notifier(&time_cpufreq_notifier_block, CPUFREQ_TRANSITION_NOTIFIER);
-#endif
return 0;
}
}
diff -ruN linux-original/kernel/cpufreq.c linux/kernel/cpufreq.c
--- linux-original/kernel/cpufreq.c 2003-01-06 12:55:43.000000000 +0100
+++ linux/kernel/cpufreq.c 2003-01-06 13:57:18.000000000 +0100
@@ -927,17 +927,27 @@
* adjust_jiffies - adjust the system "loops_per_jiffy"
*
* This function alters the system "loops_per_jiffy" for the clock
- * speed change. Note that loops_per_jiffy is only updated if all
- * CPUs are affected - else there is a need for per-CPU loops_per_jiffy
- * values which are provided by various architectures.
+ * speed change. Note that loops_per_jiffy cannot be updated on SMP
+ * systems as each CPU might be scaled differently. So, use the arch
+ * per-CPU loops_per_jiffy value wherever possible.
*/
+#ifndef CONFIG_SMP
+static unsigned long l_p_j_ref = 0;
+static unsigned int l_p_j_ref_freq = 0;
+
static inline void adjust_jiffies(unsigned long val, struct cpufreq_freqs *ci)
{
+ if (!l_p_j_ref_freq) {
+ l_p_j_ref = loops_per_jiffy;
+ l_p_j_ref_freq = ci->old;
+ }
if ((val == CPUFREQ_PRECHANGE && ci->old < ci->new) ||
(val == CPUFREQ_POSTCHANGE && ci->old > ci->new))
- if (ci->cpu == CPUFREQ_ALL_CPUS)
- loops_per_jiffy = cpufreq_scale(loops_per_jiffy, ci->old, ci->new);
+ loops_per_jiffy = cpufreq_scale(l_p_j_ref, l_p_j_ref_freq, ci->new);
}
+#else
+#define adjust_jiffies(...)
+#endif


/**
-
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