On 26 September 2015 at 20:15, Rob Herring <robh@xxxxxxxxxx> wrote: > On 09/21/2015 09:03 AM, Tomeu Vizoso wrote: >> Add a field to struct device that instructs the device-driver core to >> defer the probe of this device until the late_initcall level. > > This is true until the next patch with moves deferred probe processing > to device_initcall_sync. So disabling this option alone won't totally > revert to current behaviour. I guess patch 21 could be reverted if > necessary. Actually, the goal with that commit was to prevent potential problems due to the increased pressure on late_initcall, as suggested by Grygorii Strashko, but I haven't found yet any evidence of it being needed, and in my testing the series boot all boards in kernelci with or without this commit. So I would just not commit it for now and only consider applying it later if someone reports a problem. >> By letting all built-in drivers to register before starting to probe, we >> can avoid any deferred probes by probing dependencies on demand. >> >> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx> >> >> --- >> >> Changes in v4: >> - Add Kconfig DELAY_DEVICE_PROBES to allow disabling delayed probing in >> machines with initcalls that depend on devices probing at a given time. >> >> drivers/base/Kconfig | 18 ++++++++++++++++++ >> drivers/base/dd.c | 7 +++++++ >> include/linux/device.h | 2 ++ >> 3 files changed, 27 insertions(+) >> >> diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig >> index 98504ec99c7d..44b5d33b1f49 100644 >> --- a/drivers/base/Kconfig >> +++ b/drivers/base/Kconfig >> @@ -324,4 +324,22 @@ config CMA_ALIGNMENT >> >> endif >> >> +config DELAY_DEVICE_PROBES >> + bool "Allow delaying the probe of some devices" > > I'd like to hide visibility of this behind EXPERT. Done. >> + default y >> + help >> + Devices can be matched to a driver and probed from the moment they >> + are registered, but early during boot their probes are likely to be >> + deferred because some dependency isn't available yet because most >> + drivers haven't been registered yet. >> + >> + Enabling this option allows the device registration code to delay the >> + probing of a specific device until device_initcall_sync, when all >> + built-in drivers have been registered already. >> + >> + In some platforms there may be implicit assumptions about when some >> + devices are probed, so enabling this option could cause problems there. >> + >> + If unsure, say Y here. >> + >> endmenu >> diff --git a/drivers/base/dd.c b/drivers/base/dd.c >> index 7dc04ee81c8b..269ea76c1a4f 100644 >> --- a/drivers/base/dd.c >> +++ b/drivers/base/dd.c >> @@ -417,6 +417,13 @@ int driver_probe_device(struct device_driver *drv, struct device *dev) >> if (!device_is_registered(dev)) >> return -ENODEV; >> >> +#if IS_ENABLED(CONFIG_DELAY_DEVICE_PROBES) > > This can be moved to the if. Done. Thanks, Tomeu >> + if (!driver_deferred_probe_enable && dev->probe_late) { >> + driver_deferred_probe_add(dev); >> + return 0; >> + } >> +#endif >> + >> pr_debug("bus: '%s': %s: matched device %s with driver %s\n", >> drv->bus->name, __func__, dev_name(dev), drv->name); >> >> diff --git a/include/linux/device.h b/include/linux/device.h >> index 8e7b806f0744..e64f4c7e243d 100644 >> --- a/include/linux/device.h >> +++ b/include/linux/device.h >> @@ -744,6 +744,7 @@ struct device_dma_parameters { >> * >> * @offline_disabled: If set, the device is permanently online. >> * @offline: Set after successful invocation of bus type's .offline(). >> + * @probe_late: If set, device will be probed in the late initcall level. >> * >> * At the lowest level, every device in a Linux system is represented by an >> * instance of struct device. The device structure contains the information >> @@ -828,6 +829,7 @@ struct device { >> >> bool offline_disabled:1; >> bool offline:1; >> + bool probe_late:1; >> }; >> >> static inline struct device *kobj_to_dev(struct kobject *kobj) >> > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html