forked from Minki/linux
driver core: Add support for linking devices during device addition
The firmware corresponding to a device (dev.fwnode) might be able to provide functional dependency information between a device and its supplier and consumer devices. Tracking this functional dependency allows optimizing device probe order and informing a supplier when all its consumers have probed (and thereby actively managing their resources). The existing device links feature allows tracking and using supplier-consumer relationships. So, this patch adds the add_links() fwnode callback to allow firmware to create device links for each device as the device is added. However, when consumer devices are added, they might not have a supplier device to link to despite needing mandatory resources/functionality from one or more suppliers. A waiting_for_suppliers list is created to track such consumers and retry linking them when new devices get added. Signed-off-by: Saravana Kannan <saravanak@google.com> Link: https://lore.kernel.org/r/20190904211126.47518-3-saravanak@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -281,7 +281,8 @@ State machine
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:c:func:`driver_bound()`.)
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* Before a consumer device is probed, presence of supplier drivers is
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verified by checking that links to suppliers are in ``DL_STATE_AVAILABLE``
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verified by checking the consumer device is not in the wait_for_suppliers
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list and by checking that links to suppliers are in ``DL_STATE_AVAILABLE``
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state. The state of the links is updated to ``DL_STATE_CONSUMER_PROBE``.
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(Call to :c:func:`device_links_check_suppliers()` from
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:c:func:`really_probe()`.)
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@ -44,6 +44,8 @@ early_param("sysfs.deprecated", sysfs_deprecated_setup);
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#endif
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/* Device links support. */
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static LIST_HEAD(wait_for_suppliers);
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static DEFINE_MUTEX(wfs_lock);
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#ifdef CONFIG_SRCU
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static DEFINE_MUTEX(device_links_lock);
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@ -430,6 +432,58 @@ struct device_link *device_link_add(struct device *consumer,
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}
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EXPORT_SYMBOL_GPL(device_link_add);
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/**
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* device_link_wait_for_supplier - Add device to wait_for_suppliers list
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* @consumer: Consumer device
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*
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* Marks the @consumer device as waiting for suppliers to become available by
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* adding it to the wait_for_suppliers list. The consumer device will never be
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* probed until it's removed from the wait_for_suppliers list.
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*
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* The caller is responsible for adding the links to the supplier devices once
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* they are available and removing the @consumer device from the
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* wait_for_suppliers list once links to all the suppliers have been created.
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*
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* This function is NOT meant to be called from the probe function of the
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* consumer but rather from code that creates/adds the consumer device.
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*/
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static void device_link_wait_for_supplier(struct device *consumer)
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{
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mutex_lock(&wfs_lock);
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list_add_tail(&consumer->links.needs_suppliers, &wait_for_suppliers);
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mutex_unlock(&wfs_lock);
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}
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/**
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* device_link_add_missing_supplier_links - Add links from consumer devices to
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* supplier devices, leaving any
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* consumer with inactive suppliers on
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* the wait_for_suppliers list
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*
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* Loops through all consumers waiting on suppliers and tries to add all their
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* supplier links. If that succeeds, the consumer device is removed from
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* wait_for_suppliers list. Otherwise, they are left in the wait_for_suppliers
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* list. Devices left on the wait_for_suppliers list will not be probed.
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*
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* The fwnode add_links callback is expected to return 0 if it has found and
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* added all the supplier links for the consumer device. It should return an
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* error if it isn't able to do so.
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*
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* The caller of device_link_wait_for_supplier() is expected to call this once
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* it's aware of potential suppliers becoming available.
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*/
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static void device_link_add_missing_supplier_links(void)
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{
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struct device *dev, *tmp;
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mutex_lock(&wfs_lock);
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list_for_each_entry_safe(dev, tmp, &wait_for_suppliers,
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links.needs_suppliers)
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if (!fwnode_call_int_op(dev->fwnode, add_links, dev))
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list_del_init(&dev->links.needs_suppliers);
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mutex_unlock(&wfs_lock);
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}
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static void device_link_free(struct device_link *link)
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{
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while (refcount_dec_not_one(&link->rpm_active))
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@ -564,6 +618,17 @@ int device_links_check_suppliers(struct device *dev)
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struct device_link *link;
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int ret = 0;
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/*
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* Device waiting for supplier to become available is not allowed to
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* probe.
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*/
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mutex_lock(&wfs_lock);
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if (!list_empty(&dev->links.needs_suppliers)) {
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mutex_unlock(&wfs_lock);
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return -EPROBE_DEFER;
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}
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mutex_unlock(&wfs_lock);
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device_links_write_lock();
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list_for_each_entry(link, &dev->links.suppliers, c_node) {
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@ -848,6 +913,10 @@ static void device_links_purge(struct device *dev)
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{
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struct device_link *link, *ln;
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mutex_lock(&wfs_lock);
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list_del(&dev->links.needs_suppliers);
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mutex_unlock(&wfs_lock);
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/*
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* Delete all of the remaining links from this device to any other
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* devices (either consumers or suppliers).
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@ -1712,6 +1781,7 @@ void device_initialize(struct device *dev)
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#endif
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INIT_LIST_HEAD(&dev->links.consumers);
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INIT_LIST_HEAD(&dev->links.suppliers);
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INIT_LIST_HEAD(&dev->links.needs_suppliers);
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dev->links.status = DL_DEV_NO_DRIVER;
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}
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EXPORT_SYMBOL_GPL(device_initialize);
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@ -2202,6 +2272,24 @@ int device_add(struct device *dev)
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if (dev->fwnode && !dev->fwnode->dev)
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dev->fwnode->dev = dev;
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/*
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* Check if any of the other devices (consumers) have been waiting for
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* this device (supplier) to be added so that they can create a device
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* link to it.
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*
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* This needs to happen after device_pm_add() because device_link_add()
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* requires the supplier be registered before it's called.
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*
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* But this also needs to happe before bus_probe_device() to make sure
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* waiting consumers can link to it before the driver is bound to the
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* device and the driver sync_state callback is called for this device.
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*/
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device_link_add_missing_supplier_links();
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if (fwnode_has_op(dev->fwnode, add_links)
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&& fwnode_call_int_op(dev->fwnode, add_links, dev))
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device_link_wait_for_supplier(dev);
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bus_probe_device(dev);
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if (parent)
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klist_add_tail(&dev->p->knode_parent,
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@ -1135,11 +1135,13 @@ enum dl_dev_state {
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* struct dev_links_info - Device data related to device links.
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* @suppliers: List of links to supplier devices.
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* @consumers: List of links to consumer devices.
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* @needs_suppliers: Hook to global list of devices waiting for suppliers.
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* @status: Driver status information.
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*/
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struct dev_links_info {
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struct list_head suppliers;
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struct list_head consumers;
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struct list_head needs_suppliers;
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enum dl_dev_state status;
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};
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@ -66,6 +66,21 @@ struct fwnode_reference_args {
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* endpoint node.
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* @graph_get_port_parent: Return the parent node of a port node.
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* @graph_parse_endpoint: Parse endpoint for port and endpoint id.
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* @add_links: Called after the device corresponding to the fwnode is added
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* using device_add(). The function is expected to create device
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* links to all the suppliers of the device that are available at
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* the time this function is called. The function must NOT stop
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* at the first failed device link if other unlinked supplier
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* devices are present in the system. If some suppliers are not
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* yet available, this function will be called again when other
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* devices are added to allow creating device links to any newly
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* available suppliers.
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*
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* Return 0 if device links have been successfully created to all
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* the suppliers of this device or if the supplier information is
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* not known. Return an error if and only if the supplier
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* information is known but some of the suppliers are not yet
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* available to create device links to.
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*/
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struct fwnode_operations {
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struct fwnode_handle *(*get)(struct fwnode_handle *fwnode);
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@ -103,6 +118,8 @@ struct fwnode_operations {
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(*graph_get_port_parent)(struct fwnode_handle *fwnode);
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int (*graph_parse_endpoint)(const struct fwnode_handle *fwnode,
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struct fwnode_endpoint *endpoint);
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int (*add_links)(const struct fwnode_handle *fwnode,
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struct device *dev);
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};
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#define fwnode_has_op(fwnode, op) \
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