[PATCH v1 1/5] of/platform: Speed up of_find_device_by_node()

From: Saravana Kannan
Date: Thu May 23 2019 - 21:04:32 EST


Add a pointer from device tree node to the device created from it.
This allows us to find the device corresponding to a device tree node
without having to loop through all the platform devices.

However, fallback to looping through the platform devices to handle
any devices that might set their own of_node.

Signed-off-by: Saravana Kannan <saravanak@xxxxxxxxxx>
---
drivers/of/platform.c | 20 +++++++++++++++++++-
include/linux/of.h | 3 +++
2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index 04ad312fd85b..1115a8d80a33 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c
@@ -42,6 +42,8 @@ static int of_dev_node_match(struct device *dev, void *data)
return dev->of_node == data;
}

+static DEFINE_SPINLOCK(of_dev_lock);
+
/**
* of_find_device_by_node - Find the platform_device associated with a node
* @np: Pointer to device tree node
@@ -55,7 +57,18 @@ struct platform_device *of_find_device_by_node(struct device_node *np)
{
struct device *dev;

- dev = bus_find_device(&platform_bus_type, NULL, np, of_dev_node_match);
+ /*
+ * Spinlock needed to make sure np->dev doesn't get freed between NULL
+ * check inside and kref count increment inside get_device(). This is
+ * achieved by grabbing the spinlock before setting np->dev = NULL in
+ * of_platform_device_destroy().
+ */
+ spin_lock(&of_dev_lock);
+ dev = get_device(np->dev);
+ spin_unlock(&of_dev_lock);
+ if (!dev)
+ dev = bus_find_device(&platform_bus_type, NULL, np,
+ of_dev_node_match);
return dev ? to_platform_device(dev) : NULL;
}
EXPORT_SYMBOL(of_find_device_by_node);
@@ -196,6 +209,7 @@ static struct platform_device *of_platform_device_create_pdata(
platform_device_put(dev);
goto err_clear_flag;
}
+ np->dev = &dev->dev;

return dev;

@@ -556,6 +570,10 @@ int of_platform_device_destroy(struct device *dev, void *data)
if (of_node_check_flag(dev->of_node, OF_POPULATED_BUS))
device_for_each_child(dev, NULL, of_platform_device_destroy);

+ /* Spinlock is needed for of_find_device_by_node() to work */
+ spin_lock(&of_dev_lock);
+ dev->of_node->dev = NULL;
+ spin_unlock(&of_dev_lock);
of_node_clear_flag(dev->of_node, OF_POPULATED);
of_node_clear_flag(dev->of_node, OF_POPULATED_BUS);

diff --git a/include/linux/of.h b/include/linux/of.h
index 0cf857012f11..f2b4912cbca1 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -48,6 +48,8 @@ struct property {
struct of_irq_controller;
#endif

+struct device;
+
struct device_node {
const char *name;
phandle phandle;
@@ -68,6 +70,7 @@ struct device_node {
unsigned int unique_id;
struct of_irq_controller *irq_trans;
#endif
+ struct device *dev; /* Device created from this node */
};

#define MAX_PHANDLE_ARGS 16
--
2.22.0.rc1.257.g3120a18244-goog