of: Keep track of populated platform devices
In "Device Tree powered" systems, platform devices are usually massively
populated with of_platform_populate() call, executed at some level of
initcalls, either by generic architecture or by platform-specific code.
There are situations though where certain devices must be created (and
bound with drivers) before all the others. This presents a challenge,
as devices created explicitly would be created again by
of_platform_populate().
This patch tries to solve that issue in a generic way, adding a
"populated" flag for a DT node description. Subsequent
of_platform_populate() will skip such nodes (and its children) in
a similar way to the non-available ones.
This patch also adds of_platform_depopulate() as an operation
complementary to the _populate() one. It removes a platform or an amba
device populated from the Device Tree, together with its all children
(leaving, however, devices without associated of_node untouched)
clearing the "populated" flag on the way.
Signed-off-by: Pawel Moll <pawel.moll@arm.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Grant Likely <grant.likely@linaro.org>
diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index bd47fbc..e8376d6 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c
@@ -206,12 +206,13 @@
{
struct platform_device *dev;
- if (!of_device_is_available(np))
+ if (!of_device_is_available(np) ||
+ of_node_test_and_set_flag(np, OF_POPULATED))
return NULL;
dev = of_device_alloc(np, bus_id, parent);
if (!dev)
- return NULL;
+ goto err_clear_flag;
#if defined(CONFIG_MICROBLAZE)
dev->archdata.dma_mask = 0xffffffffUL;
@@ -229,10 +230,14 @@
if (of_device_add(dev) != 0) {
platform_device_put(dev);
- return NULL;
+ goto err_clear_flag;
}
return dev;
+
+err_clear_flag:
+ of_node_clear_flag(np, OF_POPULATED);
+ return NULL;
}
/**
@@ -264,14 +269,15 @@
pr_debug("Creating amba device %s\n", node->full_name);
- if (!of_device_is_available(node))
+ if (!of_device_is_available(node) ||
+ of_node_test_and_set_flag(node, OF_POPULATED))
return NULL;
dev = amba_device_alloc(NULL, 0, 0);
if (!dev) {
pr_err("%s(): amba_device_alloc() failed for %s\n",
__func__, node->full_name);
- return NULL;
+ goto err_clear_flag;
}
/* setup generic device info */
@@ -311,6 +317,8 @@
err_free:
amba_device_put(dev);
+err_clear_flag:
+ of_node_clear_flag(node, OF_POPULATED);
return NULL;
}
#else /* CONFIG_ARM_AMBA */
@@ -487,4 +495,60 @@
return rc;
}
EXPORT_SYMBOL_GPL(of_platform_populate);
+
+static int of_platform_device_destroy(struct device *dev, void *data)
+{
+ bool *children_left = data;
+
+ /* Do not touch devices not populated from the device tree */
+ if (!dev->of_node || !of_node_check_flag(dev->of_node, OF_POPULATED)) {
+ *children_left = true;
+ return 0;
+ }
+
+ /* Recurse, but don't touch this device if it has any children left */
+ if (of_platform_depopulate(dev) != 0) {
+ *children_left = true;
+ return 0;
+ }
+
+ if (dev->bus == &platform_bus_type)
+ platform_device_unregister(to_platform_device(dev));
+#ifdef CONFIG_ARM_AMBA
+ else if (dev->bus == &amba_bustype)
+ amba_device_unregister(to_amba_device(dev));
+#endif
+ else {
+ *children_left = true;
+ return 0;
+ }
+
+ of_node_clear_flag(dev->of_node, OF_POPULATED);
+
+ return 0;
+}
+
+/**
+ * of_platform_depopulate() - Remove devices populated from device tree
+ * @parent: device which childred will be removed
+ *
+ * Complementary to of_platform_populate(), this function removes children
+ * of the given device (and, recurrently, their children) that have been
+ * created from their respective device tree nodes (and only those,
+ * leaving others - eg. manually created - unharmed).
+ *
+ * Returns 0 when all children devices have been removed or
+ * -EBUSY when some children remained.
+ */
+int of_platform_depopulate(struct device *parent)
+{
+ bool children_left = false;
+
+ device_for_each_child(parent, &children_left,
+ of_platform_device_destroy);
+
+ return children_left ? -EBUSY : 0;
+}
+EXPORT_SYMBOL_GPL(of_platform_depopulate);
+
#endif /* CONFIG_OF_ADDRESS */
diff --git a/include/linux/of.h b/include/linux/of.h
index 3bad8d1..4c50d0b 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -130,6 +130,12 @@
return test_bit(flag, &n->_flags);
}
+static inline int of_node_test_and_set_flag(struct device_node *n,
+ unsigned long flag)
+{
+ return test_and_set_bit(flag, &n->_flags);
+}
+
static inline void of_node_set_flag(struct device_node *n, unsigned long flag)
{
set_bit(flag, &n->_flags);
@@ -197,6 +203,7 @@
/* flag descriptions */
#define OF_DYNAMIC 1 /* node and properties were allocated via kmalloc */
#define OF_DETACHED 2 /* node has been detached from the device tree */
+#define OF_POPULATED 3 /* device already created for the node */
#define OF_IS_DYNAMIC(x) test_bit(OF_DYNAMIC, &x->_flags)
#define OF_MARK_DYNAMIC(x) set_bit(OF_DYNAMIC, &x->_flags)
diff --git a/include/linux/of_platform.h b/include/linux/of_platform.h
index 05cb4a9..b1010ee 100644
--- a/include/linux/of_platform.h
+++ b/include/linux/of_platform.h
@@ -72,6 +72,7 @@
const struct of_device_id *matches,
const struct of_dev_auxdata *lookup,
struct device *parent);
+extern int of_platform_depopulate(struct device *parent);
#else
static inline int of_platform_populate(struct device_node *root,
const struct of_device_id *matches,
@@ -80,6 +81,10 @@
{
return -ENODEV;
}
+static inline int of_platform_depopulate(struct device *parent)
+{
+ return -ENODEV;
+}
#endif
#endif /* _LINUX_OF_PLATFORM_H */