| Message ID | 20180708133459.24883-1-javierm@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi, On Sun, Jul 08, 2018 at 03:34:59PM +0200, Javier Martinez Canillas wrote: > With Device Trees (DT), the dependencies of the devices are defined in the > DT, then the drivers parse that information to lookup the needed resources > that have as dependencies. > > Since drivers and devices are registered in a non-deterministic way, it is > possible that a device that is a dependency has not been registered yet by > the time that is looked up. > > In this case the driver that requires this dependency cannot probe and has > to defer it. So the driver core adds it to a list of deferred devices that > is iterated again every time that a new driver is probed successfully. > > For debugging purposes it may be useful to know what are the devices whose > probe function was deferred. Add a debugfs entry showing that information. > > $ cat /sys/kernel/debug/devices_deferred > 48070000.i2c:twl@48:bci > musb-hdrc.0.auto > omapdrm.0 > > This information could be obtained partially by enabling debugging, but it > means that the kernel log has to be parsed and the probe deferral balanced > with the successes. This can be error probe and has to be done in a ad-hoc > manner by everyone who needs to debug these kind of issues. > > Since the information is already known by the kernel, just show it to make > it easier to debug. > > Signed-off-by: Javier Martinez Canillas <javierm@redhat.com> > Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> > Reviewed-by: Mark Brown <broonie@kernel.org> Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk> -- Sebastian > --- > > Changes since RFC v1: > - Remove unneeded ret variable from deferred_devs_show() > > Changes since RFC v2: > - Use DEFINE_SHOW_ATTRIBUTE() macro. > - Don't propagate debugfs_create_file() error. > - Remove IS_ENABLED(CONFIG_DEBUG_FS) guards. > - Drop RFC prefix. > > Changes since v1: > - Better explain in the commit message why this patch is useful. > - Rename deferred_devices entry to devices_deferred. > - Add an exit function and remove the debugfs entry. > > Changes since v2: > - Add Andy Shevchenko and Mark Brown Reviewed-by tag. > - Rebase on top of Greg's driver-core-next branch. > > Changes since v3: > - Fixed a build warning caused by a wrong conflict resolution on v3. > > > drivers/base/dd.c | 29 +++++++++++++++++++++++++++++ > 1 file changed, 29 insertions(+) > > diff --git a/drivers/base/dd.c b/drivers/base/dd.c > index 6ea9c5cece7..e85705e8440 100644 > --- a/drivers/base/dd.c > +++ b/drivers/base/dd.c > @@ -16,6 +16,7 @@ > * Copyright (c) 2007-2009 Novell Inc. > */ > > +#include <linux/debugfs.h> > #include <linux/device.h> > #include <linux/delay.h> > #include <linux/dma-mapping.h> > @@ -53,6 +54,7 @@ static DEFINE_MUTEX(deferred_probe_mutex); > static LIST_HEAD(deferred_probe_pending_list); > static LIST_HEAD(deferred_probe_active_list); > static atomic_t deferred_trigger_count = ATOMIC_INIT(0); > +static struct dentry *deferred_devices; > > /* > * In some cases, like suspend to RAM or hibernation, It might be reasonable > @@ -199,6 +201,24 @@ void device_unblock_probing(void) > driver_deferred_probe_trigger(); > } > > +/* > + * deferred_devs_show() - Show the devices in the deferred probe pending list. > + */ > +static int deferred_devs_show(struct seq_file *s, void *data) > +{ > + struct device_private *curr; > + > + mutex_lock(&deferred_probe_mutex); > + > + list_for_each_entry(curr, &deferred_probe_pending_list, deferred_probe) > + seq_printf(s, "%s\n", dev_name(curr->device)); > + > + mutex_unlock(&deferred_probe_mutex); > + > + return 0; > +} > +DEFINE_SHOW_ATTRIBUTE(deferred_devs); > + > /** > * deferred_probe_initcall() - Enable probing of deferred devices > * > @@ -208,6 +228,9 @@ void device_unblock_probing(void) > */ > static int deferred_probe_initcall(void) > { > + deferred_devices = debugfs_create_file("devices_deferred", 0444, NULL, > + NULL, &deferred_devs_fops); > + > driver_deferred_probe_enable = true; > driver_deferred_probe_trigger(); > /* Sort as many dependencies as possible before exiting initcalls */ > @@ -216,6 +239,12 @@ static int deferred_probe_initcall(void) > } > late_initcall(deferred_probe_initcall); > > +static void __exit deferred_probe_exit(void) > +{ > + debugfs_remove_recursive(deferred_devices); > +} > +__exitcall(deferred_probe_exit); > + > /** > * device_is_bound() - Check if device is bound to a driver > * @dev: device to check > -- > 2.17.1 >
Hi! > > With Device Trees (DT), the dependencies of the devices are defined in the > > DT, then the drivers parse that information to lookup the needed resources > > that have as dependencies. > > > > Since drivers and devices are registered in a non-deterministic way, it is > > possible that a device that is a dependency has not been registered yet by > > the time that is looked up. > > > > In this case the driver that requires this dependency cannot probe and has > > to defer it. So the driver core adds it to a list of deferred devices that > > is iterated again every time that a new driver is probed successfully. > > > > For debugging purposes it may be useful to know what are the devices whose > > probe function was deferred. Add a debugfs entry showing that information. > > > > $ cat /sys/kernel/debug/devices_deferred > > 48070000.i2c:twl@48:bci > > musb-hdrc.0.auto > > omapdrm.0 > > > > This information could be obtained partially by enabling debugging, but it > > means that the kernel log has to be parsed and the probe deferral balanced > > with the successes. This can be error probe and has to be done in a ad-hoc > > manner by everyone who needs to debug these kind of issues. > > > > Since the information is already known by the kernel, just show it to make > > it easier to debug. > > > > Signed-off-by: Javier Martinez Canillas <javierm@redhat.com> > > Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> > > Reviewed-by: Mark Brown <broonie@kernel.org> > > Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk> Thanks for doing this. Note that it rejects on current -rc4, but solution is trivial. Tested-by: Pavel Machek <pavel@ucw.cz> Unfortunately, it does not help with pwm problem on Droid4, as nothing is deffered: user@devuan:/sys/bus/platform/drivers$ cat /sys/kernel/debug/devices_deferred user@devuan:/sys/bus/platform/drivers$ Pavel
diff --git a/drivers/base/dd.c b/drivers/base/dd.c index 6ea9c5cece7..e85705e8440 100644 --- a/drivers/base/dd.c +++ b/drivers/base/dd.c @@ -16,6 +16,7 @@ * Copyright (c) 2007-2009 Novell Inc. */ +#include <linux/debugfs.h> #include <linux/device.h> #include <linux/delay.h> #include <linux/dma-mapping.h> @@ -53,6 +54,7 @@ static DEFINE_MUTEX(deferred_probe_mutex); static LIST_HEAD(deferred_probe_pending_list); static LIST_HEAD(deferred_probe_active_list); static atomic_t deferred_trigger_count = ATOMIC_INIT(0); +static struct dentry *deferred_devices; /* * In some cases, like suspend to RAM or hibernation, It might be reasonable @@ -199,6 +201,24 @@ void device_unblock_probing(void) driver_deferred_probe_trigger(); } +/* + * deferred_devs_show() - Show the devices in the deferred probe pending list. + */ +static int deferred_devs_show(struct seq_file *s, void *data) +{ + struct device_private *curr; + + mutex_lock(&deferred_probe_mutex); + + list_for_each_entry(curr, &deferred_probe_pending_list, deferred_probe) + seq_printf(s, "%s\n", dev_name(curr->device)); + + mutex_unlock(&deferred_probe_mutex); + + return 0; +} +DEFINE_SHOW_ATTRIBUTE(deferred_devs); + /** * deferred_probe_initcall() - Enable probing of deferred devices * @@ -208,6 +228,9 @@ void device_unblock_probing(void) */ static int deferred_probe_initcall(void) { + deferred_devices = debugfs_create_file("devices_deferred", 0444, NULL, + NULL, &deferred_devs_fops); + driver_deferred_probe_enable = true; driver_deferred_probe_trigger(); /* Sort as many dependencies as possible before exiting initcalls */ @@ -216,6 +239,12 @@ static int deferred_probe_initcall(void) } late_initcall(deferred_probe_initcall); +static void __exit deferred_probe_exit(void) +{ + debugfs_remove_recursive(deferred_devices); +} +__exitcall(deferred_probe_exit); + /** * device_is_bound() - Check if device is bound to a driver * @dev: device to check