On Wed, 13 Feb 2019 at 13:01, Sudeep Holla <sudeep.ho...@arm.com> wrote: > > All device objects in the driver model contain fields that control the > handling of various power management activities. However, it's not > always useful. There are few instances where pseudo devices are added > to the model just to take advantage of many other features like > kobjects, udev events, and so on. One such example is cpu devices and > their caches. > > The sysfs for the cpu caches are managed by adding devices with cpu > as the parent in cpu_device_create() when secondary cpu is brought > online. Generally when the secondary CPUs are hotplugged back in as part > of resume from suspend-to-ram, we call cpu_device_create() from the cpu > hotplug state machine while the cpu device associated with that CPU is > not yet ready to be resumed as the device_resume() call happens bit > later. It's not really needed to set the flag is_prepared for cpu > devices as they are mostly pseudo device and hotplug framework deals > with state machine and not managed through the cpu device. > > This often results in annoying warning when resuming: > Enabling non-boot CPUs ... > CPU1: Booted secondary processor > cache: parent cpu1 should not be sleeping > CPU1 is up > CPU2: Booted secondary processor > cache: parent cpu2 should not be sleeping > CPU2 is up > .... and so on. > > So in order to fix these kind of errors, we could just completely avoid > doing any power management related initialisations and operations if > they are not used by these devices. > > Lets add no_pm_required flags to indicate that the device doesn't > require any sort of pm activities and all of them can be completely > skipped. We can use the same flag to also avoid adding not used *power* > sysfs entries for these devices. For now, lets use this for cpu cache > devices. > > Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org> > Cc: "Rafael J. Wysocki" <raf...@kernel.org> > Signed-off-by: Sudeep Holla <sudeep.ho...@arm.com>
Reviewed-by: Ulf Hansson <ulf.hans...@linaro.org> Kind regards Uffe > --- > drivers/base/cpu.c | 1 + > drivers/base/power/main.c | 7 +++++++ > drivers/base/power/sysfs.c | 4 ++++ > include/linux/device.h | 10 ++++++++++ > include/linux/pm.h | 1 + > 5 files changed, 23 insertions(+) > > v1->v2: > - dropped setting the flag for cpu devices, for now just cpu caches > will make use of this new flag. > > RFC->v1: > - dropped the idea of adding cpu hotplug callback to deal just > with cpu devices, instead add a new flag in the device pm_info > structure > > [RFC] : https://marc.info/?l=linux-pm&m=154842896407904&w=2 > [v1] : https://marc.info/?l=linux-pm&m=154946578717730&w=2 > > diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c > index eb9443d5bae1..6ce93a52bf3f 100644 > --- a/drivers/base/cpu.c > +++ b/drivers/base/cpu.c > @@ -427,6 +427,7 @@ __cpu_device_create(struct device *parent, void *drvdata, > dev->parent = parent; > dev->groups = groups; > dev->release = device_create_release; > + device_set_pm_not_required(dev); > dev_set_drvdata(dev, drvdata); > > retval = kobject_set_name_vargs(&dev->kobj, fmt, args); > diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c > index 0992e67e862b..2a29c3d4e240 100644 > --- a/drivers/base/power/main.c > +++ b/drivers/base/power/main.c > @@ -124,6 +124,10 @@ void device_pm_unlock(void) > */ > void device_pm_add(struct device *dev) > { > + /* No need to create pm sysfs if explicitly specified as not required > */ > + if (device_pm_not_required(dev)) > + return; > + > pr_debug("PM: Adding info for %s:%s\n", > dev->bus ? dev->bus->name : "No Bus", dev_name(dev)); > device_pm_check_callbacks(dev); > @@ -142,6 +146,9 @@ void device_pm_add(struct device *dev) > */ > void device_pm_remove(struct device *dev) > { > + if (device_pm_not_required(dev)) > + return; > + > pr_debug("PM: Removing info for %s:%s\n", > dev->bus ? dev->bus->name : "No Bus", dev_name(dev)); > complete_all(&dev->power.completion); > diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c > index d713738ce796..6cd159b51114 100644 > --- a/drivers/base/power/sysfs.c > +++ b/drivers/base/power/sysfs.c > @@ -648,6 +648,10 @@ int dpm_sysfs_add(struct device *dev) > { > int rc; > > + /* No need to create pm sysfs if explicitly disabled */ > + if (device_pm_not_required(dev)) > + return 0; > + > rc = sysfs_create_group(&dev->kobj, &pm_attr_group); > if (rc) > return rc; > diff --git a/include/linux/device.h b/include/linux/device.h > index 6cb4640b6160..739d0b62e4d4 100644 > --- a/include/linux/device.h > +++ b/include/linux/device.h > @@ -1165,6 +1165,16 @@ static inline bool device_async_suspend_enabled(struct > device *dev) > return !!dev->power.async_suspend; > } > > +static inline bool device_pm_not_required(struct device *dev) > +{ > + return dev->power.no_pm_required; > +} > + > +static inline void device_set_pm_not_required(struct device *dev) > +{ > + dev->power.no_pm_required = true; > +} > + > static inline void dev_pm_syscore_device(struct device *dev, bool val) > { > #ifdef CONFIG_PM_SLEEP > diff --git a/include/linux/pm.h b/include/linux/pm.h > index 0bd9de116826..300ab9f0b858 100644 > --- a/include/linux/pm.h > +++ b/include/linux/pm.h > @@ -592,6 +592,7 @@ struct dev_pm_info { > bool is_suspended:1; /* Ditto */ > bool is_noirq_suspended:1; > bool is_late_suspended:1; > + bool no_pm_required:1; > bool early_init:1; /* Owned by the PM core */ > bool direct_complete:1; /* Owned by the PM > core */ > u32 driver_flags; > -- > 2.17.1 >
