cpufreq: Update Documentation for cpus and related_cpus

Commit Message

Viresh Kumar Jan. 31, 2013, 2:03 a.m. UTC

Documentation related to cpus and related_cpus is confusing and not very clear.
Over that CPUFreq core has seen much changes recently. Lets update documentation
and comments for cpus and related_cpus.

Signed-off-by: Viresh Kumar <[e-mail]>
---
 Documentation/cpu-freq/cpu-drivers.txt | 6 ++++++
 Documentation/cpu-freq/user-guide.txt  | 8 ++++----
 include/linux/cpufreq.h                | 6 ++++--
 3 files changed, 14 insertions(+), 6 deletions(-)

Patch

diff --git a/Documentation/cpu-freq/cpu-drivers.txt b/Documentation/cpu-freq/cpu-drivers.txt
index c436096..72f70b1 100644
--- a/Documentation/cpu-freq/cpu-drivers.txt
+++ b/Documentation/cpu-freq/cpu-drivers.txt
@@ -111,6 +111,12 @@  policy->governor		must contain the "default policy" for
 For setting some of these values, the frequency table helpers might be
 helpful. See the section 2 for more information on them.
 
+SMP systems normally have same clock source for a group of cpus. For these the
+.init() would be called only once for the first online cpu. Here the .init()
+routine must initialize policy->cpus with mask of all possible cpus (Online +
+Offline) that share the clock. Then the core would copy this mask onto
+policy->related_cpus and will reset policy->cpus to carry only online cpus.
+
 
 1.3 verify
 ------------
diff --git a/Documentation/cpu-freq/user-guide.txt b/Documentation/cpu-freq/user-guide.txt
index 04f6b32..ff2f283 100644
--- a/Documentation/cpu-freq/user-guide.txt
+++ b/Documentation/cpu-freq/user-guide.txt
@@ -190,11 +190,11 @@  scaling_max_freq		show the current "policy limits" (in
 				first set scaling_max_freq, then
 				scaling_min_freq.
 
-affected_cpus :			List of CPUs that require software coordination
-				of frequency.
+affected_cpus :			List of Online CPUs that require software
+				coordination of frequency.
 
-related_cpus :			List of CPUs that need some sort of frequency
-				coordination, whether software or hardware.
+related_cpus :			List of Online + Offline CPUs that need software
+				coordination of frequency.
 
 scaling_driver :		Hardware driver for cpufreq.
 
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index b60f6ba..04d2e84 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -86,8 +86,10 @@  struct cpufreq_real_policy {
 };
 
 struct cpufreq_policy {
-	cpumask_var_t		cpus;	/* CPUs requiring sw coordination */
-	cpumask_var_t		related_cpus; /* CPUs with any coordination */
+	/* CPUs sharing clock, require sw coordination */
+	cpumask_var_t		cpus;	/* Online CPUs only */
+	cpumask_var_t		related_cpus; /* Online + Offline CPUs */
+
 	unsigned int		shared_type; /* ANY or ALL affected CPUs
 						should set cpufreq */
 	unsigned int		cpu;    /* cpu nr of registered CPU */