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Commit 3d36a0df authored by Stefan Richter's avatar Stefan Richter
Browse files

firewire: keep highlevel drivers attached during brief connection loss 



There are situations when nodes vanish from the bus and come back
quickly thereafter:
  - When certain bus-powered hubs are plugged in,
  - when certain devices are plugged into 6-port hubs,
  - when certain disk enclosures are switched from self-power to bus
    power or vice versa and break the daisy chain during the transition,
  - when the user plugs a cable out and quickly plugs it back in, e.g.
    to reorder a daisy chain (works on Mac OS X if done quickly enough),
  - when certain hubs temporarily malfunction during high bus traffic.

Until now, firewire-core reported affected nodes as lost to the
highlevel drivers (firewire-sbp2 and userspace drivers).  We now delay
the destruction of device representations until after at least two
seconds after the last bus reset.  If a "new" device is detected in this
period whose bus information block and root directory header match that
of a device which is pending for deletion, we resurrect that device and
send update calls to highlevel drivers.

Signed-off-by: default avatarStefan Richter <stefanr@s5r6.in-berlin.de>
parent 8cd0bbbd

drivers/firewire/fw-device.c

+99 −22
Original line number Diff line number Diff line
@@ -25,6 +25,7 @@ 
#include <linux/device.h>

#include <linux/delay.h>

#include <linux/idr.h>

#include <linux/jiffies.h>

#include <linux/string.h>

#include <linux/rwsem.h>

#include <linux/semaphore.h>
@@ -634,12 +635,38 @@ struct fw_device *fw_device_get_by_devt(dev_t devt) 
	return device;

}



/*

 * These defines control the retry behavior for reading the config

 * rom.  It shouldn't be necessary to tweak these; if the device

 * doesn't respond to a config rom read within 10 seconds, it's not

 * going to respond at all.  As for the initial delay, a lot of

 * devices will be able to respond within half a second after bus

 * reset.  On the other hand, it's not really worth being more

 * aggressive than that, since it scales pretty well; if 10 devices

 * are plugged in, they're all getting read within one second.

 */



#define MAX_RETRIES	10

#define RETRY_DELAY	(3 * HZ)

#define INITIAL_DELAY	(HZ / 2)

#define SHUTDOWN_DELAY	(2 * HZ)



static void fw_device_shutdown(struct work_struct *work)

{

	struct fw_device *device =

		container_of(work, struct fw_device, work.work);

	int minor = MINOR(device->device.devt);



	if (time_is_after_jiffies(device->card->reset_jiffies + SHUTDOWN_DELAY)) {

		schedule_delayed_work(&device->work, SHUTDOWN_DELAY);

		return;

	}



	if (atomic_cmpxchg(&device->state,

			   FW_DEVICE_GONE,

			   FW_DEVICE_SHUTDOWN) != FW_DEVICE_GONE)

		return;



	fw_device_cdev_remove(device);

	device_for_each_child(&device->device, NULL, shutdown_unit);

	device_unregister(&device->device);
@@ -647,6 +674,7 @@ static void fw_device_shutdown(struct work_struct *work) 
	down_write(&fw_device_rwsem);

	idr_remove(&fw_device_idr, minor);

	up_write(&fw_device_rwsem);



	fw_device_put(device);

}
@@ -654,25 +682,63 @@ static struct device_type fw_device_type = { 
	.release	= fw_device_release,

};



static void fw_device_update(struct work_struct *work);



/*

 * These defines control the retry behavior for reading the config

 * rom.  It shouldn't be necessary to tweak these; if the device

 * doesn't respond to a config rom read within 10 seconds, it's not

 * going to respond at all.  As for the initial delay, a lot of

 * devices will be able to respond within half a second after bus

 * reset.  On the other hand, it's not really worth being more

 * aggressive than that, since it scales pretty well; if 10 devices

 * are plugged in, they're all getting read within one second.

 * If a device was pending for deletion because its node went away but its

 * bus info block and root directory header matches that of a newly discovered

 * device, revive the existing fw_device.

 * The newly allocated fw_device becomes obsolete instead.

 */

static int lookup_existing_device(struct device *dev, void *data)

{

	struct fw_device *old = fw_device(dev);

	struct fw_device *new = data;

	struct fw_card *card = new->card;

	int match = 0;



	down_read(&fw_device_rwsem); /* serialize config_rom access */

	spin_lock_irq(&card->lock);  /* serialize node access */



	if (memcmp(old->config_rom, new->config_rom, 6 * 4) == 0 &&

	    atomic_cmpxchg(&old->state,

			   FW_DEVICE_GONE,

			   FW_DEVICE_RUNNING) == FW_DEVICE_GONE) {

		struct fw_node *current_node = new->node;

		struct fw_node *obsolete_node = old->node;



		new->node = obsolete_node;

		new->node->data = new;

		old->node = current_node;

		old->node->data = old;



		old->max_speed = new->max_speed;

		old->node_id = current_node->node_id;

		smp_wmb();  /* update node_id before generation */

		old->generation = card->generation;

		old->config_rom_retries = 0;

		fw_notify("rediscovered device %s\n", dev_name(dev));



#define MAX_RETRIES	10

#define RETRY_DELAY	(3 * HZ)

#define INITIAL_DELAY	(HZ / 2)

		PREPARE_DELAYED_WORK(&old->work, fw_device_update);

		schedule_delayed_work(&old->work, 0);



		if (current_node == card->root_node)

			fw_schedule_bm_work(card, 0);



		match = 1;

	}



	spin_unlock_irq(&card->lock);

	up_read(&fw_device_rwsem);



	return match;

}



static void fw_device_init(struct work_struct *work)

{

	struct fw_device *device =

		container_of(work, struct fw_device, work.work);

	struct device *revived_dev;

	int minor, err;



	/*
@@ -696,6 +762,15 @@ static void fw_device_init(struct work_struct *work) 
		return;

	}



	revived_dev = device_find_child(device->card->device,

					device, lookup_existing_device);

	if (revived_dev) {

		put_device(revived_dev);

		fw_device_release(&device->device);



		return;

	}



	device_initialize(&device->device);



	fw_device_get(device);
@@ -735,8 +810,9 @@ static void fw_device_init(struct work_struct *work) 
	 */

	if (atomic_cmpxchg(&device->state,

			   FW_DEVICE_INITIALIZING,

		    FW_DEVICE_RUNNING) == FW_DEVICE_SHUTDOWN) {

		fw_device_shutdown(work);

			   FW_DEVICE_RUNNING) == FW_DEVICE_GONE) {

		PREPARE_DELAYED_WORK(&device->work, fw_device_shutdown);

		schedule_delayed_work(&device->work, SHUTDOWN_DELAY);

	} else {

		if (device->config_rom_retries)

			fw_notify("created device %s: GUID %08x%08x, S%d00, "
@@ -848,7 +924,7 @@ static void fw_device_refresh(struct work_struct *work) 
	case REREAD_BIB_UNCHANGED:

		if (atomic_cmpxchg(&device->state,

				   FW_DEVICE_INITIALIZING,

			    FW_DEVICE_RUNNING) == FW_DEVICE_SHUTDOWN)

				   FW_DEVICE_RUNNING) == FW_DEVICE_GONE)

			goto gone;



		fw_device_update(work);
@@ -880,7 +956,7 @@ static void fw_device_refresh(struct work_struct *work) 


	if (atomic_cmpxchg(&device->state,

			   FW_DEVICE_INITIALIZING,

		    FW_DEVICE_RUNNING) == FW_DEVICE_SHUTDOWN)

			   FW_DEVICE_RUNNING) == FW_DEVICE_GONE)

		goto gone;



	fw_notify("refreshed device %s\n", dev_name(&device->device));
@@ -890,8 +966,9 @@ static void fw_device_refresh(struct work_struct *work) 
 give_up:

	fw_notify("giving up on refresh of device %s\n", dev_name(&device->device));

 gone:

	atomic_set(&device->state, FW_DEVICE_SHUTDOWN);

	fw_device_shutdown(work);

	atomic_set(&device->state, FW_DEVICE_GONE);

	PREPARE_DELAYED_WORK(&device->work, fw_device_shutdown);

	schedule_delayed_work(&device->work, SHUTDOWN_DELAY);

 out:

	if (node_id == card->root_node->node_id)

		fw_schedule_bm_work(card, 0);
@@ -995,9 +1072,9 @@ void fw_node_event(struct fw_card *card, struct fw_node *node, int event) 
		 */

		device = node->data;

		if (atomic_xchg(&device->state,

				FW_DEVICE_SHUTDOWN) == FW_DEVICE_RUNNING) {

				FW_DEVICE_GONE) == FW_DEVICE_RUNNING) {

			PREPARE_DELAYED_WORK(&device->work, fw_device_shutdown);

			schedule_delayed_work(&device->work, 0);

			schedule_delayed_work(&device->work, SHUTDOWN_DELAY);

		}

		break;

	}

drivers/firewire/fw-device.h

+1 −0
Original line number Diff line number Diff line
@@ -28,6 +28,7 @@ 
enum fw_device_state {

	FW_DEVICE_INITIALIZING,

	FW_DEVICE_RUNNING,

	FW_DEVICE_GONE,

	FW_DEVICE_SHUTDOWN,

};