[PATCH 1/2] cpufreq: Add stop callback to cpufreq_driver interface

From: dirk . brandewie
Date: Tue Mar 18 2014 - 13:23:50 EST

From: Dirk Brandewie <dirk.j.brandewie@xxxxxxxxx>

This callback allows the driver to do clean up before the CPU is
completely down and its state cannot be modified. This is used
by the intel_pstate driver to reduce the requested P state prior to
the core going away. This is required because the requested P state
of the offline core is used to select the package P state. This
effectively sets the floor package P state to the requested P state on
the offline core.

Signed-off-by: Dirk Brandewie <dirk.j.brandewie@xxxxxxxxx>
Documentation/cpu-freq/cpu-drivers.txt | 8 +++++++-
drivers/cpufreq/cpufreq.c | 3 ++-
include/linux/cpufreq.h | 1 +
3 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/Documentation/cpu-freq/cpu-drivers.txt b/Documentation/cpu-freq/cpu-drivers.txt
index 8b1a445..79def80 100644
--- a/Documentation/cpu-freq/cpu-drivers.txt
+++ b/Documentation/cpu-freq/cpu-drivers.txt
@@ -61,7 +61,13 @@ target_index - See below on the differences.

And optionally

-cpufreq_driver.exit - A pointer to a per-CPU cleanup function.
+cpufreq_driver.exit - A pointer to a per-CPU cleanup
+ function called during CPU_POST_DEAD
+ phase of cpu hotplug process.
+cpufreq_driver.stop - A pointer to a per-CPU stop function
+ called during CPU_DOWN_PREPARE phase of
+ cpu hotplug process.

cpufreq_driver.resume - A pointer to a per-CPU resume function
which is called with interrupts disabled
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index cf485d9..6e6beae 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1336,7 +1336,8 @@ static int __cpufreq_remove_dev_prepare(struct device *dev,
__func__, new_cpu, cpu);
- }
+ } else if (cpufreq_driver->stop)
+ cpufreq_driver->stop(policy);

return 0;
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 4d89e0e..ff8db19 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -224,6 +224,7 @@ struct cpufreq_driver {
int (*bios_limit) (int cpu, unsigned int *limit);

int (*exit) (struct cpufreq_policy *policy);
+ int (*stop) (struct cpufreq_policy *policy);
int (*suspend) (struct cpufreq_policy *policy);
int (*resume) (struct cpufreq_policy *policy);
struct freq_attr **attr;

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