linux-kernel - [PATCH v2 1/2] cpufreq: Add exit_prepare callback to cpufreq

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Date:	Fri, 14 Mar 2014 14:03:56 -0700
From:	dirk.brandewie@...il.com
To:	linux-pm@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, rjw@...ysocki.net,
	patrick.marlier@...il.com, dirk.brandewie@...il.com,
	Dirk Brandewie <dirk.j.brandewie@...el.com>
Subject: [PATCH v2 1/2] cpufreq: Add exit_prepare callback to cpufreq_driver interface

From: Dirk Brandewie <dirk.j.brandewie@...el.com>

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@...el.com>
---
 Documentation/cpu-freq/cpu-drivers.txt | 8 +++++++-
 drivers/cpufreq/cpufreq.c              | 3 +++
 include/linux/cpufreq.h                | 1 +
 3 files changed, 11 insertions(+), 1 deletion(-)

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..0d430d7 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1338,6 +1338,9 @@ static int __cpufreq_remove_dev_prepare(struct device *dev,
 		}
 	}
 
+	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;
-- 
1.8.3.1

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