Commit ffbe08a8 authored by Saravana Kannan's avatar Saravana Kannan Committed by Greg Kroah-Hartman
Browse files

driver core: Add fw_devlink.sync_state command line param 



When all devices that could probe have finished probing (based on
deferred_probe_timeout configuration or late_initcall() when
!CONFIG_MODULES), this parameter controls what to do with devices that
haven't yet received their sync_state() calls.

fw_devlink.sync_state=strict is the default and the driver core will
continue waiting on all consumers of a device to probe successfully
before sync_state() is called for the device. This is the default
behavior since calling sync_state() on a device when all its consumers
haven't probed could make some systems unusable/unstable. When this
option is selected, we also print the list of devices that haven't had
sync_state() called on them by the time all devices the could probe have
finished probing.

fw_devlink.sync_state=timeout will cause the driver core to give up
waiting on consumers and call sync_state() on any devices that haven't
yet received their sync_state() calls. This option is provided for
systems that won't become unusable/unstable as they might be able to
save power (depends on state of hardware before kernel starts) if all
devices get their sync_state().

Signed-off-by: default avatarSaravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20230304005355.746421-2-saravanak@google.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 22fd6153

Documentation/admin-guide/kernel-parameters.txt

+14 −0
Original line number Diff line number Diff line
@@ -1582,6 +1582,20 @@ 
			dependencies. This only applies for fw_devlink=on|rpm.

			Format: <bool>



	fw_devlink.sync_state =

			[KNL] When all devices that could probe have finished

			probing, this parameter controls what to do with

			devices that haven't yet received their sync_state()

			calls.

			Format: { strict | timeout }

			strict -- Default. Continue waiting on consumers to

				probe successfully.

			timeout -- Give up waiting on consumers and call

				sync_state() on any devices that haven't yet

				received their sync_state() calls after

				deferred_probe_timeout has expired or by

				late_initcall() if !CONFIG_MODULES.



	gamecon.map[2|3]=

			[HW,JOY] Multisystem joystick and NES/SNES/PSX pad

			support via parallel port (up to 5 devices per port)

drivers/base/base.h

+1 −0
Original line number Diff line number Diff line
@@ -209,6 +209,7 @@ 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);

extern void fw_devlink_drivers_done(void);

extern void fw_devlink_probing_done(void);



/* device pm support */

void device_pm_move_to_tail(struct device *dev);

drivers/base/core.c

+58 −0
Original line number Diff line number Diff line
@@ -1672,6 +1672,26 @@ static int __init fw_devlink_strict_setup(char *arg) 
}

early_param("fw_devlink.strict", fw_devlink_strict_setup);



#define FW_DEVLINK_SYNC_STATE_STRICT	0

#define FW_DEVLINK_SYNC_STATE_TIMEOUT	1



static int fw_devlink_sync_state;

static int __init fw_devlink_sync_state_setup(char *arg)

{

	if (!arg)

		return -EINVAL;



	if (strcmp(arg, "strict") == 0) {

		fw_devlink_sync_state = FW_DEVLINK_SYNC_STATE_STRICT;

		return 0;

	} else if (strcmp(arg, "timeout") == 0) {

		fw_devlink_sync_state = FW_DEVLINK_SYNC_STATE_TIMEOUT;

		return 0;

	}

	return -EINVAL;

}

early_param("fw_devlink.sync_state", fw_devlink_sync_state_setup);



static inline u32 fw_devlink_get_flags(u8 fwlink_flags)

{

	if (fwlink_flags & FWLINK_FLAG_CYCLE)
@@ -1742,6 +1762,44 @@ void fw_devlink_drivers_done(void) 
	device_links_write_unlock();

}



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

{

	struct device_link *link = to_devlink(dev);

	struct device *sup = link->supplier;



	if (!(link->flags & DL_FLAG_MANAGED) ||

	    link->status == DL_STATE_ACTIVE || sup->state_synced ||

	    !dev_has_sync_state(sup))

		return 0;



	if (fw_devlink_sync_state == FW_DEVLINK_SYNC_STATE_STRICT) {

		dev_warn(sup, "sync_state() pending due to %s\n",

			 dev_name(link->consumer));

		return 0;

	}



	if (!list_empty(&sup->links.defer_sync))

		return 0;



	dev_warn(sup, "Timed out. Forcing sync_state()\n");

	sup->state_synced = true;

	get_device(sup);

	list_add_tail(&sup->links.defer_sync, data);



	return 0;

}



void fw_devlink_probing_done(void)

{

	LIST_HEAD(sync_list);



	device_links_write_lock();

	class_for_each_device(&devlink_class, NULL, &sync_list,

			      fw_devlink_dev_sync_state);

	device_links_write_unlock();

	device_links_flush_sync_list(&sync_list, NULL);

}



/**

 * wait_for_init_devices_probe - Try to probe any device needed for init

 *

drivers/base/dd.c

+6 −0
Original line number Diff line number Diff line
@@ -315,6 +315,8 @@ static void deferred_probe_timeout_work_func(struct work_struct *work) 
	list_for_each_entry(p, &deferred_probe_pending_list, deferred_probe)

		dev_info(p->device, "deferred probe pending\n");

	mutex_unlock(&deferred_probe_mutex);



	fw_devlink_probing_done();

}

static DECLARE_DELAYED_WORK(deferred_probe_timeout_work, deferred_probe_timeout_work_func);
@@ -364,6 +366,10 @@ static int deferred_probe_initcall(void) 
		schedule_delayed_work(&deferred_probe_timeout_work,

			driver_deferred_probe_timeout * HZ);

	}



	if (!IS_ENABLED(CONFIG_MODULES))

		fw_devlink_probing_done();



	return 0;

}

late_initcall(deferred_probe_initcall);