Hi Marek, On Fri, Jun 17, 2016 at 08:26:52AM +0200, Marek Szyprowski wrote: > From: "Rafael J. Wysocki" <rafael.j.wysocki@xxxxxxxxx> > > Currently, there is a problem with handling cases where functional > dependencies between devices are involved. > > What I mean by a "functional dependency" is when the driver of device > B needs both device A and its driver to be present and functional to > be able to work. This implies that the driver of A needs to be > working for B to be probed successfully and it cannot be unbound from > the device before the B's driver. This also has certain consequences > for power management of these devices (suspend/resume and runtime PM > ordering). > > Add support for representing those functional dependencies between > devices to allow the driver core to track them and act on them in > certain cases where they matter. Rafael has indicated that he intends to respin this series: https://lkml.org/lkml/2016/6/8/1061 We also have such a functional dependency for Thunderbolt on Macs: On resume from system sleep, the PCIe hotplug ports may not resume before the thunderbolt driver has reestablished the PCI tunnels. Currently this is enforced by quirk_apple_wait_for_thunderbolt() in drivers/pci/quirks.c. It would be good if we could represent this dependency using something like Rafael's approach instead of open coding it, however one detail in Rafael's patches is problematic: > New links are added by calling device_link_add() which may happen > either before the consumer device is probed or when probing it, in > which case the caller needs to ensure that the driver of the > supplier device is present and functional and the DEVICE_LINK_PROBE_TIME > flag should be passed to device_link_add() to reflect that. The thunderbolt driver cannot call device_link_add() before the PCIe hotplug ports are bound to a driver unless we amend portdrv to return -EPROBE_DEFER for Thunderbolt hotplug ports on Macs if the thunderbolt driver isn't loaded. It would therefore be beneficial if device_link_add() can be called even *after* the consumer is bound. Thanks, Lukas > > Link objects are deleted either explicitly, by calling > device_link_del() on the link object in question, or automatically, > when the consumer device is unbound from its driver or when one > of the target devices is deleted, depending on the link type. > > There are two types of link objects, persistent and non-persistent. > The difference between them is that the persistent links stay around > until one of the target devices is deleted, which the non-persistent > ones are deleted when the consumer driver is unbound from its device > (ie. they are assumed to be valid only as long as the consumer device > has a driver bound to it). The DEVICE_LINK_PERSISTENT flag has to > be passed to device_link_add() so as to create a persistent link. > > One of the actions carried out by device_link_add() is to reorder > the lists used for device shutdown and system suspend/resume to > put the consumer device along with all of its children and all of > its consumers (and so on, recursively) to the ends of those list > in order to ensure the right ordering between the all of the supplier > and consumer devices. > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> > --- > drivers/base/base.h | 11 ++ > drivers/base/core.c | 386 +++++++++++++++++++++++++++++++++++++++++++++++++ > drivers/base/dd.c | 42 +++++- > include/linux/device.h | 36 +++++ > 4 files changed, 470 insertions(+), 5 deletions(-) > > diff --git a/drivers/base/base.h b/drivers/base/base.h > index e05db388bd1c..cccb1d211541 100644 > --- a/drivers/base/base.h > +++ b/drivers/base/base.h > @@ -107,6 +107,9 @@ extern void bus_remove_device(struct device *dev); > > extern int bus_add_driver(struct device_driver *drv); > extern void bus_remove_driver(struct device_driver *drv); > +extern void device_release_driver_internal(struct device *dev, > + struct device_driver *drv, > + struct device *parent); > > extern void driver_detach(struct device_driver *drv); > extern int driver_probe_device(struct device_driver *drv, struct device *dev); > @@ -152,3 +155,11 @@ extern int devtmpfs_init(void); > #else > static inline int devtmpfs_init(void) { return 0; } > #endif > + > +/* Device links */ > +extern int device_links_check_suppliers(struct device *dev); > +extern void device_links_driver_bound(struct device *dev); > +extern void device_links_driver_gone(struct device *dev); > +extern void device_links_no_driver(struct device *dev); > +extern bool device_links_busy(struct device *dev); > +extern void device_links_unbind_consumers(struct device *dev); > diff --git a/drivers/base/core.c b/drivers/base/core.c > index 0a8bdade53f2..416341df3268 100644 > --- a/drivers/base/core.c > +++ b/drivers/base/core.c > @@ -44,6 +44,367 @@ static int __init sysfs_deprecated_setup(char *arg) > early_param("sysfs.deprecated", sysfs_deprecated_setup); > #endif > > +/* Device links support. */ > + > +DEFINE_STATIC_SRCU(device_links_srcu); > +static DEFINE_MUTEX(device_links_lock); > + > +static int device_reorder_to_tail(struct device *dev, void *not_used) > +{ > + struct devlink *link; > + > + devices_kset_move_last(dev); > + device_pm_move_last(dev); > + device_for_each_child(dev, NULL, device_reorder_to_tail); > + list_for_each_entry(link, &dev->consumer_links, c_node) > + device_reorder_to_tail(link->consumer, NULL); > + > + return 0; > +} > + > +/** > + * device_link_add - Create a link between two devices. > + * @consumer: Consumer end of the link. > + * @supplier: Supplier end of the link. > + * @flags: Link flags. > + * > + * At least one of the flags must be set. If DEVICE_LINK_PROBE_TIME is set, the > + * caller is expected to know that (a) the supplier device is present and active > + * (ie. its driver is functional) and (b) the consumer device is probing at the > + * moment and therefore the initial state of the link will be "consumer probe" > + * in that case. If DEVICE_LINK_PROBE_TIME is not set, DEVICE_LINK_PERSISTENT > + * must be set (meaning that the link will not go away when the consumer driver > + * goes away). > + * > + * A side effect of the link creation is re-ordering of dpm_list and the > + * devices_kset list by moving the consumer device and all devices depending > + * on it to the ends of those lists. > + */ > +struct devlink *device_link_add(struct device *consumer, > + struct device *supplier, u32 flags) > +{ > + struct devlink *link; > + > + if (!consumer || !supplier || !flags) > + return NULL; > + > + mutex_lock(&device_links_lock); > + > + list_for_each_entry(link, &supplier->supplier_links, s_node) > + if (link->consumer == consumer) > + goto out; > + > + link = kmalloc(sizeof(*link), GFP_KERNEL); > + if (!link) > + goto out; > + > + get_device(supplier); > + link->supplier = supplier; > + INIT_LIST_HEAD(&link->s_node); > + get_device(consumer); > + link->consumer = consumer; > + INIT_LIST_HEAD(&link->c_node); > + link->flags = flags; > + link->status = (flags & DEVICE_LINK_PROBE_TIME) ? > + DEVICE_LINK_CONSUMER_PROBE : DEVICE_LINK_DORMANT; > + spin_lock_init(&link->lock); > + > + /* > + * Move the consumer and all of the devices depending on it to the end > + * of dpm_list and the devices_kset list. > + * > + * We have to hold dpm_list locked throughout all that or else we may > + * end up suspending with a wrong ordering of it. > + */ > + device_pm_lock(); > + device_reorder_to_tail(consumer, NULL); > + device_pm_unlock(); > + > + list_add_tail_rcu(&link->s_node, &supplier->supplier_links); > + list_add_tail_rcu(&link->c_node, &consumer->consumer_links); > + > + dev_info(consumer, "Linked as a consumer to %s\n", dev_name(supplier)); > + > + out: > + mutex_unlock(&device_links_lock); > + return link; > +} > +EXPORT_SYMBOL_GPL(device_link_add); > + > +static void __devlink_free_srcu(struct rcu_head *rhead) > +{ > + struct devlink *link; > + > + link = container_of(rhead, struct devlink, rcu_head); > + put_device(link->consumer); > + put_device(link->supplier); > + kfree(link); > +} > + > +static void devlink_del(struct devlink *link) > +{ > + dev_info(link->consumer, "Dropping the link to %s\n", > + dev_name(link->supplier)); > + > + list_del_rcu(&link->s_node); > + list_del_rcu(&link->c_node); > + call_srcu(&device_links_srcu, &link->rcu_head, __devlink_free_srcu); > +} > + > +/** > + * device_link_del - Delete a link between two devices. > + * @link: Device link to delete. > + */ > +void device_link_del(struct devlink *link) > +{ > + mutex_lock(&device_links_lock); > + devlink_del(link); > + mutex_unlock(&device_links_lock); > +} > +EXPORT_SYMBOL_GPL(device_link_del); > + > +static int device_links_read_lock(void) > +{ > + return srcu_read_lock(&device_links_srcu); > +} > + > +static void device_links_read_unlock(int idx) > +{ > + return srcu_read_unlock(&device_links_srcu, idx); > +} > + > +static void device_links_missing_supplier(struct device *dev) > +{ > + struct devlink *link; > + > + list_for_each_entry_rcu(link, &dev->consumer_links, c_node) { > + spin_lock(&link->lock); > + > + if (link->status == DEVICE_LINK_CONSUMER_PROBE) > + link->status = DEVICE_LINK_AVAILABLE; > + > + spin_unlock(&link->lock); > + } > +} > + > +/** > + * device_links_check_suppliers - Check supplier devices for this one. > + * @dev: Consumer device. > + * > + * Check links from this device to any suppliers. Walk the list of the device's > + * consumer links and see if all of the suppliers are available. If not, simply > + * return -EPROBE_DEFER. > + * > + * Walk the list under SRCU and check each link's status field under its lock. > + * > + * We need to guarantee that the supplier will not go away after the check has > + * been positive here. It only can go away in __device_release_driver() and > + * that function checks the device's links to consumers. This means we need to > + * mark the link as "consumer probe in progress" to make the supplier removal > + * wait for us to complete (or bad things may happen). > + */ > +int device_links_check_suppliers(struct device *dev) > +{ > + struct devlink *link; > + int idx, ret = 0; > + > + idx = device_links_read_lock(); > + > + list_for_each_entry_rcu(link, &dev->consumer_links, c_node) { > + spin_lock(&link->lock); > + if (link->status != DEVICE_LINK_AVAILABLE) { > + spin_unlock(&link->lock); > + device_links_missing_supplier(dev); > + ret = -EPROBE_DEFER; > + break; > + } > + link->status = DEVICE_LINK_CONSUMER_PROBE; > + spin_unlock(&link->lock); > + } > + > + device_links_read_unlock(idx); > + return ret; > +} > + > +/** > + * device_links_driver_bound - Update device links after probing its driver. > + * @dev: Device to update the links for. > + * > + * The probe has been successful, so update links from this device to any > + * consumers by changing their status to "available". > + * > + * Also change the status of @dev's links to suppliers to "active". > + */ > +void device_links_driver_bound(struct device *dev) > +{ > + struct devlink *link; > + int idx; > + > + idx = device_links_read_lock(); > + > + list_for_each_entry_rcu(link, &dev->supplier_links, s_node) { > + spin_lock(&link->lock); > + WARN_ON(link->status != DEVICE_LINK_DORMANT); > + link->status = DEVICE_LINK_AVAILABLE; > + spin_unlock(&link->lock); > + } > + > + list_for_each_entry_rcu(link, &dev->consumer_links, c_node) { > + spin_lock(&link->lock); > + WARN_ON(link->status != DEVICE_LINK_CONSUMER_PROBE); > + link->status = DEVICE_LINK_ACTIVE; > + spin_unlock(&link->lock); > + } > + > + device_links_read_unlock(idx); > +} > + > +/** > + * device_links_driver_gone - Update links after driver removal. > + * @dev: Device whose driver has gone away. > + * > + * Update links to consumers for @dev by changing their status to "dormant". > + */ > +void device_links_driver_gone(struct device *dev) > +{ > + struct devlink *link; > + int idx; > + > + idx = device_links_read_lock(); > + > + list_for_each_entry_rcu(link, &dev->supplier_links, s_node) { > + WARN_ON(!(link->flags & DEVICE_LINK_PERSISTENT)); > + spin_lock(&link->lock); > + WARN_ON(link->status != DEVICE_LINK_SUPPLIER_UNBIND); > + link->status = DEVICE_LINK_DORMANT; > + spin_unlock(&link->lock); > + } > + > + device_links_read_unlock(idx); > +} > + > +/** > + * device_links_no_driver - Update links of a device without a driver. > + * @dev: Device without a drvier. > + * > + * Delete all non-persistent links from this device to any suppliers. > + * Persistent links stay around, but their status is changed to "available", > + * unless they already are in the "supplier unbind in progress" state in which > + * case they need not be updated. > + */ > +void device_links_no_driver(struct device *dev) > +{ > + struct devlink *link, *ln; > + > + mutex_lock(&device_links_lock); > + > + list_for_each_entry_safe_reverse(link, ln, &dev->consumer_links, c_node) > + if (link->flags & DEVICE_LINK_PERSISTENT) { > + spin_lock(&link->lock); > + > + if (link->status != DEVICE_LINK_SUPPLIER_UNBIND) > + link->status = DEVICE_LINK_AVAILABLE; > + > + spin_unlock(&link->lock); > + } else { > + devlink_del(link); > + } > + > + mutex_unlock(&device_links_lock); > +} > + > +/** > + * device_links_busy - Check if there are any busy links to consumers. > + * @dev: Device to check. > + * > + * Check each consumer of the device and return 'true' it if its link's status > + * is one of "consumer probe" or "active" (meaning that the given consumer is > + * probing right now or its driver is present). Otherwise, change the link > + * state to "supplier unbind" to prevent the consumer from being probed > + * successfully going forward. > + * > + * Return 'false' if there are no probing or active consumers. > + */ > +bool device_links_busy(struct device *dev) > +{ > + struct devlink *link; > + int idx; > + bool ret = false; > + > + idx = device_links_read_lock(); > + > + list_for_each_entry_rcu(link, &dev->supplier_links, s_node) { > + spin_lock(&link->lock); > + if (link->status == DEVICE_LINK_CONSUMER_PROBE > + || link->status == DEVICE_LINK_ACTIVE) { > + spin_unlock(&link->lock); > + ret = true; > + break; > + } > + link->status = DEVICE_LINK_SUPPLIER_UNBIND; > + spin_unlock(&link->lock); > + } > + > + device_links_read_unlock(idx); > + return ret; > +} > + > +/** > + * device_links_unbind_consumers - Force unbind consumers of the given device. > + * @dev: Device to unbind the consumers of. > + * > + * Walk the list of links to consumers for @dev and if any of them is in the > + * "consumer probe" state, wait for all device probes in progress to complete > + * and start over. > + * > + * If that's not the case, change the status of the link to "supplier unbind" > + * and check if the link was in the "active" state. If so, force the consumer > + * driver to unbind and start over (the consumer will not re-probe as we have > + * changed the state of the link already). > + */ > +void device_links_unbind_consumers(struct device *dev) > +{ > + struct devlink *link; > + int idx; > + > + start: > + idx = device_links_read_lock(); > + > + list_for_each_entry_rcu(link, &dev->supplier_links, s_node) { > + enum devlink_status status; > + > + spin_lock(&link->lock); > + status = link->status; > + if (status == DEVICE_LINK_CONSUMER_PROBE) { > + spin_unlock(&link->lock); > + > + device_links_read_unlock(idx); > + > + wait_for_device_probe(); > + goto start; > + } > + link->status = DEVICE_LINK_SUPPLIER_UNBIND; > + if (status == DEVICE_LINK_ACTIVE) { > + struct device *consumer = link->consumer; > + > + get_device(consumer); > + spin_unlock(&link->lock); > + > + device_links_read_unlock(idx); > + > + device_release_driver_internal(consumer, NULL, > + consumer->parent); > + put_device(consumer); > + goto start; > + } > + spin_unlock(&link->lock); > + } > + > + device_links_read_unlock(idx); > +} > + > +/* Device links support end. */ > + > int (*platform_notify)(struct device *dev) = NULL; > int (*platform_notify_remove)(struct device *dev) = NULL; > static struct kobject *dev_kobj; > @@ -711,6 +1072,8 @@ void device_initialize(struct device *dev) > #ifdef CONFIG_GENERIC_MSI_IRQ > INIT_LIST_HEAD(&dev->msi_list); > #endif > + INIT_LIST_HEAD(&dev->supplier_links); > + INIT_LIST_HEAD(&dev->consumer_links); > } > EXPORT_SYMBOL_GPL(device_initialize); > > @@ -1233,6 +1596,7 @@ void device_del(struct device *dev) > { > struct device *parent = dev->parent; > struct class_interface *class_intf; > + struct devlink *link, *ln; > > /* Notify clients of device removal. This call must come > * before dpm_sysfs_remove(). > @@ -1240,6 +1604,28 @@ void device_del(struct device *dev) > if (dev->bus) > blocking_notifier_call_chain(&dev->bus->p->bus_notifier, > BUS_NOTIFY_DEL_DEVICE, dev); > + > + /* > + * Delete all of the remaining links from this device to any other > + * devices (either consumers or suppliers). > + * > + * This requires that all links be dormant, so warn if that's no the > + * case. > + */ > + mutex_lock(&device_links_lock); > + > + list_for_each_entry_safe_reverse(link, ln, &dev->consumer_links, c_node) { > + WARN_ON(link->status != DEVICE_LINK_DORMANT); > + devlink_del(link); > + } > + > + list_for_each_entry_safe_reverse(link, ln, &dev->supplier_links, s_node) { > + WARN_ON(link->status != DEVICE_LINK_DORMANT); > + devlink_del(link); > + } > + > + mutex_unlock(&device_links_lock); > + > dpm_sysfs_remove(dev); > if (parent) > klist_del(&dev->p->knode_parent); > diff --git a/drivers/base/dd.c b/drivers/base/dd.c > index d9e76e9205c7..7c0abeba89e9 100644 > --- a/drivers/base/dd.c > +++ b/drivers/base/dd.c > @@ -249,6 +249,7 @@ static void driver_bound(struct device *dev) > __func__, dev_name(dev)); > > klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices); > + device_links_driver_bound(dev); > > device_pm_check_callbacks(dev); > > @@ -399,6 +400,7 @@ probe_failed: > blocking_notifier_call_chain(&dev->bus->p->bus_notifier, > BUS_NOTIFY_DRIVER_NOT_BOUND, dev); > pinctrl_bind_failed: > + device_links_no_driver(dev); > devres_release_all(dev); > driver_sysfs_remove(dev); > dev->driver = NULL; > @@ -489,6 +491,10 @@ int driver_probe_device(struct device_driver *drv, struct device *dev) > if (!device_is_registered(dev)) > return -ENODEV; > > + ret = device_links_check_suppliers(dev); > + if (ret) > + return ret; > + > pr_debug("bus: '%s': %s: matched device %s with driver %s\n", > drv->bus->name, __func__, dev_name(dev), drv->name); > > @@ -756,7 +762,7 @@ EXPORT_SYMBOL_GPL(driver_attach); > * __device_release_driver() must be called with @dev lock held. > * When called for a USB interface, @dev->parent lock must be held as well. > */ > -static void __device_release_driver(struct device *dev) > +static void __device_release_driver(struct device *dev, struct device *parent) > { > struct device_driver *drv; > > @@ -765,6 +771,25 @@ static void __device_release_driver(struct device *dev) > if (driver_allows_async_probing(drv)) > async_synchronize_full(); > > + while (device_links_busy(dev)) { > + device_unlock(dev); > + if (parent) > + device_unlock(parent); > + > + device_links_unbind_consumers(dev); > + if (parent) > + device_lock(parent); > + > + device_lock(dev); > + /* > + * A concurrent invocation of the same function might > + * have released the driver successfully while this one > + * was waiting, so check for that. > + */ > + if (dev->driver != drv) > + return; > + } > + > pm_runtime_get_sync(dev); > > driver_sysfs_remove(dev); > @@ -780,6 +805,9 @@ static void __device_release_driver(struct device *dev) > dev->bus->remove(dev); > else if (drv->remove) > drv->remove(dev); > + > + device_links_driver_gone(dev); > + device_links_no_driver(dev); > devres_release_all(dev); > dev->driver = NULL; > dev_set_drvdata(dev, NULL); > @@ -796,16 +824,16 @@ static void __device_release_driver(struct device *dev) > } > } > > -static void device_release_driver_internal(struct device *dev, > - struct device_driver *drv, > - struct device *parent) > +void device_release_driver_internal(struct device *dev, > + struct device_driver *drv, > + struct device *parent) > { > if (parent) > device_lock(parent); > > device_lock(dev); > if (!drv || drv == dev->driver) > - __device_release_driver(dev); > + __device_release_driver(dev, parent); > > device_unlock(dev); > if (parent) > @@ -818,6 +846,10 @@ static void device_release_driver_internal(struct device *dev, > * > * Manually detach device from driver. > * When called for a USB interface, @dev->parent lock must be held. > + * > + * If this function is to be called with @dev->parent lock held, ensure that > + * the device's consumers are unbound in advance or that their locks can be > + * acquired under the @dev->parent lock. > */ > void device_release_driver(struct device *dev) > { > diff --git a/include/linux/device.h b/include/linux/device.h > index 38f02814d53a..647204bd74a0 100644 > --- a/include/linux/device.h > +++ b/include/linux/device.h > @@ -706,6 +706,34 @@ struct device_dma_parameters { > unsigned long segment_boundary_mask; > }; > > +enum devlink_status { > + DEVICE_LINK_DORMANT = 0, /* Link not in use. */ > + DEVICE_LINK_AVAILABLE, /* Supplier driver is present. */ > + DEVICE_LINK_ACTIVE, /* Consumer driver is present too. */ > + DEVICE_LINK_CONSUMER_PROBE, /* Consumer is probing. */ > + DEVICE_LINK_SUPPLIER_UNBIND, /* Supplier is unbinding. */ > +}; > + > +/* > + * Device link flags. > + * > + * PERSISTENT: Do not delete the link on consumer device driver unbind. > + * PROBE_TIME: Assume supplier device functional when creating the link. > + */ > +#define DEVICE_LINK_PERSISTENT (1 << 0) > +#define DEVICE_LINK_PROBE_TIME (1 << 1) > + > +struct devlink { > + struct device *supplier; > + struct list_head s_node; > + struct device *consumer; > + struct list_head c_node; > + enum devlink_status status; > + u32 flags; > + spinlock_t lock; > + struct rcu_head rcu_head; > +}; > + > /** > * struct device - The basic device structure > * @parent: The device's "parent" device, the device to which it is attached. > @@ -731,6 +759,8 @@ struct device_dma_parameters { > * on. This shrinks the "Board Support Packages" (BSPs) and > * minimizes board-specific #ifdefs in drivers. > * @driver_data: Private pointer for driver specific info. > + * @supplier_links: Links to consumer devices. > + * @consumer_links: Links to supplier devices. > * @power: For device power management. > * See Documentation/power/devices.txt for details. > * @pm_domain: Provide callbacks that are executed during system suspend, > @@ -797,6 +827,8 @@ struct device { > core doesn't touch it */ > void *driver_data; /* Driver data, set and get with > dev_set/get_drvdata */ > + struct list_head supplier_links; > + struct list_head consumer_links; > struct dev_pm_info power; > struct dev_pm_domain *pm_domain; > > @@ -1113,6 +1145,10 @@ extern void device_shutdown(void); > /* debugging and troubleshooting/diagnostic helpers. */ > extern const char *dev_driver_string(const struct device *dev); > > +/* Device links interface. */ > +struct devlink *device_link_add(struct device *consumer, > + struct device *supplier, u32 flags); > +void device_link_del(struct devlink *link); > > #ifdef CONFIG_PRINTK > > -- > 1.9.1 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-pm" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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