PM: Reference counting of power.subsys_data

Since the power.subsys_data device field will be used by multiple
filesystems, introduce a reference counting mechanism for it to avoid
freeing it prematurely or changing its value at a wrong time.

Make the PM clocks management code that currently is the only user of
power.subsys_data use the new reference counting.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

3 files changed, 93 insertions, 20 deletions

diff --git a/drivers/base/power/Makefile b/drivers/base/power/Makefile
index 2639ae79a372..6488ce12f586 100644
--- a/drivers/base/power/Makefile
+++ b/drivers/base/power/Makefile
@@ -1,4 +1,4 @@
-obj-$(CONFIG_PM)        += sysfs.o generic_ops.o
+obj-$(CONFIG_PM)        += sysfs.o generic_ops.o common.o
 obj-$(CONFIG_PM_SLEEP)  += main.o wakeup.o
 obj-$(CONFIG_PM_RUNTIME)        += runtime.o
 obj-$(CONFIG_PM_TRACE_RTC)      += trace.o
diff --git a/drivers/base/power/clock_ops.c b/drivers/base/power/clock_ops.c
index b7f1db4f5945..8383e2488d79 100644
--- a/drivers/base/power/clock_ops.c
+++ b/drivers/base/power/clock_ops.c
@@ -140,12 +140,8 @@ void pm_clk_remove(struct device *dev, const char *con_id)
 void pm_clk_init(struct device *dev)
 {
         struct pm_subsys_data *psd = dev_to_psd(dev);
-
-        if (!psd)
-                return;
-
-        INIT_LIST_HEAD(&psd->clock_list);
-        spin_lock_init(&psd->lock);
+        if (psd)
+                INIT_LIST_HEAD(&psd->clock_list);
 }
 
 /**
@@ -157,16 +153,8 @@ void pm_clk_init(struct device *dev)
  */
 int pm_clk_create(struct device *dev)
 {
-        struct pm_subsys_data *psd;
-
-        psd = kzalloc(sizeof(*psd), GFP_KERNEL);
-        if (!psd) {
-                dev_err(dev, "Not enough memory for PM clock data.\n");
-                return -ENOMEM;
-        }
-        dev->power.subsys_data = psd;
-        pm_clk_init(dev);
-        return 0;
+        int ret = dev_pm_get_subsys_data(dev);
+        return ret < 0 ? ret : 0;
 }
 
 /**
@@ -185,8 +173,6 @@ void pm_clk_destroy(struct device *dev)
         if (!psd)
                 return;
 
-        dev->power.subsys_data = NULL;
-
         spin_lock_irq(&psd->lock);
 
         list_for_each_entry_safe_reverse(ce, c, &psd->clock_list, node)
@@ -194,7 +180,7 @@ void pm_clk_destroy(struct device *dev)
 
         spin_unlock_irq(&psd->lock);
 
-        kfree(psd);
+        dev_pm_put_subsys_data(dev);
 }
 
 #endif /* CONFIG_PM */
diff --git a/drivers/base/power/common.c b/drivers/base/power/common.c
new file mode 100644
index 000000000000..d398cf029b32
--- /dev/null
+++ b/drivers/base/power/common.c
@@ -0,0 +1,87 @@
+/*
+ * drivers/base/power/common.c - Common device power management code.
+ *
+ * Copyright (C) 2011 Rafael J. Wysocki <rjw@sisk.pl>, Renesas Electronics Corp.
+ *
+ * This file is released under the GPLv2.
+ */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/device.h>
+#include <linux/pm_runtime.h>
+
+/**
+ * dev_pm_get_subsys_data - Create or refcount power.subsys_data for device.
+ * @dev: Device to handle.
+ *
+ * If power.subsys_data is NULL, point it to a new object, otherwise increment
+ * its reference counter.  Return 1 if a new object has been created, otherwise
+ * return 0 or error code.
+ */
+int dev_pm_get_subsys_data(struct device *dev)
+{
+        struct pm_subsys_data *psd;
+        int ret = 0;
+
+        psd = kzalloc(sizeof(*psd), GFP_KERNEL);
+        if (!psd)
+                return -ENOMEM;
+
+        spin_lock_irq(&dev->power.lock);
+
+        if (dev->power.subsys_data) {
+                dev->power.subsys_data->refcount++;
+        } else {
+                spin_lock_init(&psd->lock);
+                psd->refcount = 1;
+                dev->power.subsys_data = psd;
+                pm_clk_init(dev);
+                psd = NULL;
+                ret = 1;
+        }
+
+        spin_unlock_irq(&dev->power.lock);
+
+        /* kfree() verifies that its argument is nonzero. */
+        kfree(psd);
+
+        return ret;
+}
+EXPORT_SYMBOL_GPL(dev_pm_get_subsys_data);
+
+/**
+ * dev_pm_put_subsys_data - Drop reference to power.subsys_data.
+ * @dev: Device to handle.
+ *
+ * If the reference counter of power.subsys_data is zero after dropping the
+ * reference, power.subsys_data is removed.  Return 1 if that happens or 0
+ * otherwise.
+ */
+int dev_pm_put_subsys_data(struct device *dev)
+{
+        struct pm_subsys_data *psd;
+        int ret = 0;
+
+        spin_lock_irq(&dev->power.lock);
+
+        psd = dev_to_psd(dev);
+        if (!psd) {
+                ret = -EINVAL;
+                goto out;
+        }
+
+        if (--psd->refcount == 0) {
+                dev->power.subsys_data = NULL;
+                kfree(psd);
+                ret = 1;
+        }
+
+ out:
+        spin_unlock_irq(&dev->power.lock);
+
+        return ret;
+}
+EXPORT_SYMBOL_GPL(dev_pm_put_subsys_data);