[RFC,1/2] powerpc: powernv: Framework to show the correct clock in /proc/cpuinfo

Message ID 1394537479-17231-2-git-send-email-ego@linux.vnet.ibm.com
State Accepted
Commit 2299d03a632c7586403ab43a11b418ee1ae47f1a
Headers show

Commit Message

Gautham R Shenoy March 11, 2014, 11:31 a.m.
From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>

Currently, the code in setup-common.c for powerpc assumes that all
clock rates are same in a smp system. This value is cached in the
variable named ppc_proc_freq and is the value that is reported in

However on the PowerNV platform, the clock rate is same only across
the threads of the same core. Hence the value that is reported in
/proc/cpuinfo is incorrect on PowerNV platforms. We need a better way
to query and report the correct value of the processor clock in

The patch achieves this by creating a machdep_call named
get_proc_freq() which is expected to returns the frequency in Hz. The
code in show_cpuinfo() can invoke this method to display the correct
clock rate on platforms that have implemented this method. On the
other powerpc platforms it can use the value cached in ppc_proc_freq.

Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
 arch/powerpc/include/asm/machdep.h |  2 ++
 arch/powerpc/kernel/setup-common.c | 16 ++++++++++++----
 2 files changed, 14 insertions(+), 4 deletions(-)


diff --git a/arch/powerpc/include/asm/machdep.h b/arch/powerpc/include/asm/machdep.h
index ad3025d..eb1c6d4 100644
--- a/arch/powerpc/include/asm/machdep.h
+++ b/arch/powerpc/include/asm/machdep.h
@@ -113,6 +113,8 @@  struct machdep_calls {
 	/* Optional, may be NULL. */
 	void		(*show_cpuinfo)(struct seq_file *m);
 	void		(*show_percpuinfo)(struct seq_file *m, int i);
+	/* Returns the current operating frequency of "cpu" in Hz */
+	unsigned long  	(*get_proc_freq)(unsigned int cpu);
 	void		(*init_IRQ)(void);
diff --git a/arch/powerpc/kernel/setup-common.c b/arch/powerpc/kernel/setup-common.c
index bc76cc6..bdd3045 100644
--- a/arch/powerpc/kernel/setup-common.c
+++ b/arch/powerpc/kernel/setup-common.c
@@ -209,6 +209,7 @@  static int show_cpuinfo(struct seq_file *m, void *v)
 	unsigned long cpu_id = (unsigned long)v - 1;
 	unsigned int pvr;
+	unsigned long proc_freq;
 	unsigned short maj;
 	unsigned short min;
@@ -260,12 +261,19 @@  static int show_cpuinfo(struct seq_file *m, void *v)
 #endif /* CONFIG_TAU */
-	 * Assume here that all clock rates are the same in a
-	 * smp system.  -- Cort
+	 * Platforms that have variable clock rates, should implement
+	 * the method ppc_md.get_proc_freq() that reports the clock
+	 * rate of a given cpu. The rest can use ppc_proc_freq to
+	 * report the clock rate that is same across all cpus.
-	if (ppc_proc_freq)
+	if (ppc_md.get_proc_freq)
+		proc_freq = ppc_md.get_proc_freq(cpu_id);
+	else
+		proc_freq = ppc_proc_freq;
+	if (proc_freq)
 		seq_printf(m, "clock\t\t: %lu.%06luMHz\n",
-			   ppc_proc_freq / 1000000, ppc_proc_freq % 1000000);
+			   proc_freq / 1000000, proc_freq % 1000000);
 	if (ppc_md.show_percpuinfo != NULL)
 		ppc_md.show_percpuinfo(m, cpu_id);