[CPUFREQ] CPU frequency display in /proc/cpuinfo

What is the value shown in "cpu MHz" of /proc/cpuinfo when CPUs are capable of
changing frequency?

Today the answer is: It depends.
On i386:
SMP kernel - It is always the boot frequency
UP kernel - Scales with the frequency change and shows that was last set.

On x86_64:
There is one single variable cpu_khz that gets written by all the CPUs. So,
the frequency set by last CPU will be seen on /proc/cpuinfo of all the
CPUs in the system. What you see also depends on whether you have constant_tsc
capable CPU or not.

On ia64:
It is always boot time frequency of a particular CPU that gets displayed.

The patch below changes this to:
Show the last known frequency of the particular CPU, when cpufreq is present. If
cpu doesnot support changing of frequency through cpufreq, then boot frequency
will be shown. The patch affects i386, x86_64 and ia64 architectures.

Signed-off-by: Venkatesh Pallipadi<venkatesh.pallipadi@intel.com>
Signed-off-by: Dave Jones <davej@redhat.com>

3 files changed, 17 insertions, 3 deletions

diff --git a/arch/i386/kernel/cpu/proc.c b/arch/i386/kernel/cpu/proc.c
index e792131..6d91b27 100644
--- a/arch/i386/kernel/cpu/proc.c
+++ b/arch/i386/kernel/cpu/proc.c
@@ -3,6 +3,7 @@
 #include <linux/string.h>
 #include <asm/semaphore.h>
 #include <linux/seq_file.h>
+#include <linux/cpufreq.h>
 
 /*
  *	Get CPU information for use by the procfs.
@@ -86,8 +87,11 @@ static int show_cpuinfo(struct seq_file *m, void *v)
 		seq_printf(m, "stepping\t: unknown\n");
 
 	if ( cpu_has(c, X86_FEATURE_TSC) ) {
+		unsigned int freq = cpufreq_quick_get(n);
+		if (!freq)
+			freq = cpu_khz;
 		seq_printf(m, "cpu MHz\t\t: %u.%03u\n",
-			cpu_khz / 1000, (cpu_khz % 1000));
+			freq / 1000, (freq % 1000));
 	}
 
 	/* Cache size */
diff --git a/arch/ia64/kernel/setup.c b/arch/ia64/kernel/setup.c
index 5add0bc..088e5dd 100644
--- a/arch/ia64/kernel/setup.c
+++ b/arch/ia64/kernel/setup.c
@@ -43,6 +43,7 @@
 #include <linux/initrd.h>
 #include <linux/platform.h>
 #include <linux/pm.h>
+#include <linux/cpufreq.h>
 
 #include <asm/ia32.h>
 #include <asm/machvec.h>
@@ -517,6 +518,7 @@ show_cpuinfo (struct seq_file *m, void *v)
 	char family[32], features[128], *cp, sep;
 	struct cpuinfo_ia64 *c = v;
 	unsigned long mask;
+	unsigned int proc_freq;
 	int i;
 
 	mask = c->features;
@@ -549,6 +551,10 @@ show_cpuinfo (struct seq_file *m, void *v)
 		sprintf(cp, " 0x%lx", mask);
 	}
 
+	proc_freq = cpufreq_quick_get(cpunum);
+	if (!proc_freq)
+		proc_freq = c->proc_freq / 1000;
+
 	seq_printf(m,
 		   "processor  : %d\n"
 		   "vendor     : %s\n"
@@ -565,7 +571,7 @@ show_cpuinfo (struct seq_file *m, void *v)
 		   "BogoMIPS   : %lu.%02lu\n",
 		   cpunum, c->vendor, family, c->model, c->revision, c->archrev,
 		   features, c->ppn, c->number,
-		   c->proc_freq / 1000000, c->proc_freq % 1000000,
+		   proc_freq / 1000, proc_freq % 1000,
 		   c->itc_freq / 1000000, c->itc_freq % 1000000,
 		   lpj*HZ/500000, (lpj*HZ/5000) % 100);
 #ifdef CONFIG_SMP
diff --git a/arch/x86_64/kernel/setup.c b/arch/x86_64/kernel/setup.c
index 750e01d..64c4534 100644
--- a/arch/x86_64/kernel/setup.c
+++ b/arch/x86_64/kernel/setup.c
@@ -42,6 +42,7 @@
 #include <linux/edd.h>
 #include <linux/mmzone.h>
 #include <linux/kexec.h>
+#include <linux/cpufreq.h>
 
 #include <asm/mtrr.h>
 #include <asm/uaccess.h>
@@ -1256,8 +1257,11 @@ static int show_cpuinfo(struct seq_file *m, void *v)
 		seq_printf(m, "stepping\t: unknown\n");
 	
 	if (cpu_has(c,X86_FEATURE_TSC)) {
+		unsigned int freq = cpufreq_quick_get((unsigned)(c-cpu_data));
+		if (!freq)
+			freq = cpu_khz;
 		seq_printf(m, "cpu MHz\t\t: %u.%03u\n",
-			     cpu_khz / 1000, (cpu_khz % 1000));
+			     freq / 1000, (freq % 1000));
 	}
 
 	/* Cache size */