diff options
Diffstat (limited to 'drivers/base/dd.c')
| -rw-r--r-- | drivers/base/dd.c | 148 |
1 files changed, 147 insertions, 1 deletions
diff --git a/drivers/base/dd.c b/drivers/base/dd.c index 142e3d600f1..1b1cbb571d3 100644 --- a/drivers/base/dd.c +++ b/drivers/base/dd.c @@ -28,6 +28,141 @@ #include "base.h" #include "power/power.h" +/* + * Deferred Probe infrastructure. + * + * Sometimes driver probe order matters, but the kernel doesn't always have + * dependency information which means some drivers will get probed before a + * resource it depends on is available. For example, an SDHCI driver may + * first need a GPIO line from an i2c GPIO controller before it can be + * initialized. If a required resource is not available yet, a driver can + * request probing to be deferred by returning -EPROBE_DEFER from its probe hook + * + * Deferred probe maintains two lists of devices, a pending list and an active + * list. A driver returning -EPROBE_DEFER causes the device to be added to the + * pending list. A successful driver probe will trigger moving all devices + * from the pending to the active list so that the workqueue will eventually + * retry them. + * + * The deferred_probe_mutex must be held any time the deferred_probe_*_list + * of the (struct device*)->p->deferred_probe pointers are manipulated + */ +static DEFINE_MUTEX(deferred_probe_mutex); +static LIST_HEAD(deferred_probe_pending_list); +static LIST_HEAD(deferred_probe_active_list); +static struct workqueue_struct *deferred_wq; + +/** + * deferred_probe_work_func() - Retry probing devices in the active list. + */ +static void deferred_probe_work_func(struct work_struct *work) +{ + struct device *dev; + struct device_private *private; + /* + * This block processes every device in the deferred 'active' list. + * Each device is removed from the active list and passed to + * bus_probe_device() to re-attempt the probe. The loop continues + * until every device in the active list is removed and retried. + * + * Note: Once the device is removed from the list and the mutex is + * released, it is possible for the device get freed by another thread + * and cause a illegal pointer dereference. This code uses + * get/put_device() to ensure the device structure cannot disappear + * from under our feet. + */ + mutex_lock(&deferred_probe_mutex); + while (!list_empty(&deferred_probe_active_list)) { + private = list_first_entry(&deferred_probe_active_list, + typeof(*dev->p), deferred_probe); + dev = private->device; + list_del_init(&private->deferred_probe); + + get_device(dev); + + /* + * Drop the mutex while probing each device; the probe path may + * manipulate the deferred list + */ + mutex_unlock(&deferred_probe_mutex); + dev_dbg(dev, "Retrying from deferred list\n"); + bus_probe_device(dev); + mutex_lock(&deferred_probe_mutex); + + put_device(dev); + } + mutex_unlock(&deferred_probe_mutex); +} +static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func); + +static void driver_deferred_probe_add(struct device *dev) +{ + mutex_lock(&deferred_probe_mutex); + if (list_empty(&dev->p->deferred_probe)) { + dev_dbg(dev, "Added to deferred list\n"); + list_add(&dev->p->deferred_probe, &deferred_probe_pending_list); + } + mutex_unlock(&deferred_probe_mutex); +} + +void driver_deferred_probe_del(struct device *dev) +{ + mutex_lock(&deferred_probe_mutex); + if (!list_empty(&dev->p->deferred_probe)) { + dev_dbg(dev, "Removed from deferred list\n"); + list_del_init(&dev->p->deferred_probe); + } + mutex_unlock(&deferred_probe_mutex); +} + +static bool driver_deferred_probe_enable = false; +/** + * driver_deferred_probe_trigger() - Kick off re-probing deferred devices + * + * This functions moves all devices from the pending list to the active + * list and schedules the deferred probe workqueue to process them. It + * should be called anytime a driver is successfully bound to a device. + */ +static void driver_deferred_probe_trigger(void) +{ + if (!driver_deferred_probe_enable) + return; + + /* + * A successful probe means that all the devices in the pending list + * should be triggered to be reprobed. Move all the deferred devices + * into the active list so they can be retried by the workqueue + */ + mutex_lock(&deferred_probe_mutex); + list_splice_tail_init(&deferred_probe_pending_list, + &deferred_probe_active_list); + mutex_unlock(&deferred_probe_mutex); + + /* + * Kick the re-probe thread. It may already be scheduled, but it is + * safe to kick it again. + */ + queue_work(deferred_wq, &deferred_probe_work); +} + +/** + * deferred_probe_initcall() - Enable probing of deferred devices + * + * We don't want to get in the way when the bulk of drivers are getting probed. + * Instead, this initcall makes sure that deferred probing is delayed until + * late_initcall time. + */ +static int deferred_probe_initcall(void) +{ + deferred_wq = create_singlethread_workqueue("deferwq"); + if (WARN_ON(!deferred_wq)) + return -ENOMEM; + + driver_deferred_probe_enable = true; + driver_deferred_probe_trigger(); + return 0; +} +late_initcall(deferred_probe_initcall); static void driver_bound(struct device *dev) { @@ -42,6 +177,13 @@ static void driver_bound(struct device *dev) klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices); + /* + * Make sure the device is no longer in one of the deferred lists and + * kick off retrying all pending devices + */ + driver_deferred_probe_del(dev); + driver_deferred_probe_trigger(); + if (dev->bus) blocking_notifier_call_chain(&dev->bus->p->bus_notifier, BUS_NOTIFY_BOUND_DRIVER, dev); @@ -142,7 +284,11 @@ probe_failed: driver_sysfs_remove(dev); dev->driver = NULL; - if (ret != -ENODEV && ret != -ENXIO) { + if (ret == -EPROBE_DEFER) { + /* Driver requested deferred probing */ + dev_info(dev, "Driver %s requests probe deferral\n", drv->name); + driver_deferred_probe_add(dev); + } else if (ret != -ENODEV && ret != -ENXIO) { /* driver matched but the probe failed */ printk(KERN_WARNING "%s: probe of %s failed with error %d\n", |