| Message ID | 20190213120137.23354-1-sudeep.holla@arm.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] drivers: base: add support to skip power management in device/driver model | expand |
On Wed, 13 Feb 2019 at 13:01, Sudeep Holla <sudeep.holla@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 <gregkh@linuxfoundation.org> > Cc: "Rafael J. Wysocki" <rafael@kernel.org> > Signed-off-by: Sudeep Holla <sudeep.holla@arm.com> Reviewed-by: Ulf Hansson <ulf.hansson@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 >
On Wed, Feb 13, 2019 at 1:01 PM Sudeep Holla <sudeep.holla@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 <gregkh@linuxfoundation.org> > Cc: "Rafael J. Wysocki" <rafael@kernel.org> > Signed-off-by: Sudeep Holla <sudeep.holla@arm.com> > --- > 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 */ Is this really about sysfs? > + if (device_pm_not_required(dev)) Should power.disable_depth be bumped up here or while setting the "no PM" flag? > + 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; Maybe call it "no_pm"? > bool early_init:1; /* Owned by the PM core */ > bool direct_complete:1; /* Owned by the PM core */ > u32 driver_flags; > --
Hello Sudeep, I appreciate your efforts. Currently, this patch generates below warnings during s2ram on R-Car H3-Salvator-X: [ 46.874214] PM: suspend entry (deep) [ 46.878211] PM: Syncing filesystems ... done. [ 46.989148] Freezing user space processes ... (elapsed 0.004 seconds) done. [ 47.000428] OOM killer disabled. [ 47.003895] Freezing remaining freezable tasks ... (elapsed 0.003 seconds) done. [ 47.226363] PM: suspend devices took 0.210 seconds [ 47.280553] Disabling non-boot CPUs ... [ 47.289157] ------------[ cut here ]------------ [ 47.294524] sysfs group 'power' not found for kobject 'index0' [ 47.300622] WARNING: CPU: 1 PID: 14 at fs/sysfs/group.c:256 sysfs_remove_group+0x78/0xc4 ---snip--- [ 47.550425] sysfs group 'power' not found for kobject 'index1' ---snip--- [ 47.807005] sysfs group 'power' not found for kobject 'index2' ---snip--- [ 48.063703] sysfs group 'power' not found for kobject 'cache' ---snip--- Complete log and .config are shared in https://gist.github.com/erosca/da9ea551033a503121de61049d77b834 Thank you, Eugeniu.
On Wed, Feb 13, 2019 at 11:38:49PM +0100, Eugeniu Rosca wrote: > Hello Sudeep, > > I appreciate your efforts. Currently, this patch generates below > warnings during s2ram on R-Car H3-Salvator-X: > > [ 46.874214] PM: suspend entry (deep) > [ 46.878211] PM: Syncing filesystems ... done. > [ 46.989148] Freezing user space processes ... (elapsed 0.004 seconds) done. > [ 47.000428] OOM killer disabled. > [ 47.003895] Freezing remaining freezable tasks ... (elapsed 0.003 seconds) done. > [ 47.226363] PM: suspend devices took 0.210 seconds > [ 47.280553] Disabling non-boot CPUs ... > [ 47.289157] ------------[ cut here ]------------ > [ 47.294524] sysfs group 'power' not found for kobject 'index0' > [ 47.300622] WARNING: CPU: 1 PID: 14 at fs/sysfs/group.c:256 sysfs_remove_group+0x78/0xc4 > ---snip--- > [ 47.550425] sysfs group 'power' not found for kobject 'index1' > ---snip--- > [ 47.807005] sysfs group 'power' not found for kobject 'index2' > ---snip--- > [ 48.063703] sysfs group 'power' not found for kobject 'cache' > ---snip--- > Thanks for the report, looks like I am not able to reproduce this, will check if I am missing something while testing. > Complete log and .config are shared in > https://gist.github.com/erosca/da9ea551033a503121de61049d77b834 > Thanks again, much appreciated for providing full log. -- Regards, Sudeep
On Wed, Feb 13, 2019 at 11:17:47PM +0100, Rafael J. Wysocki wrote: > On Wed, Feb 13, 2019 at 1:01 PM Sudeep Holla <sudeep.holla@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 <gregkh@linuxfoundation.org> > > Cc: "Rafael J. Wysocki" <rafael@kernel.org> > > Signed-off-by: Sudeep Holla <sudeep.holla@arm.com> > > --- > > 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 */ > > Is this really about sysfs? > Nope, copy-paste from dpm_sysfs_add, will drop it. > > + if (device_pm_not_required(dev)) > > Should power.disable_depth be bumped up here or while setting the "no PM" flag? > OK, I missed that. Also I did have extra check in dpm_sysfs_remove but dropped it as redundant. Based on Eugeniu report, I need to add it back. [...] > > 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; > > Maybe call it "no_pm"? > Sure. -- Regards, Sudeep
On Thu, Feb 14, 2019 at 11:16:09AM +0000, Sudeep Holla wrote: > On Wed, Feb 13, 2019 at 11:17:47PM +0100, Rafael J. Wysocki wrote: > > On Wed, Feb 13, 2019 at 1:01 PM Sudeep Holla <sudeep.holla@arm.com> wrote: [...] > > > 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 */ > > > > Is this really about sysfs? > > > > Nope, copy-paste from dpm_sysfs_add, will drop it. > > > > + if (device_pm_not_required(dev)) > > > > Should power.disable_depth be bumped up here or while setting the "no PM" flag? > > > > OK, I missed that. > Looking at it, 1. We can't set it when we set "no PM" flag as pm_runtime_init called later initialise it to 1 2. We can bump it here, but I see it's usage self contained in runtime.c and may look odd to access it here. More basic question is should we really need to bump it to 2 as its initialised to 1 in runtime_init. -- Regards, Sudeep
On Thu, Feb 14, 2019 at 1:05 PM Sudeep Holla <sudeep.holla@arm.com> wrote: > > On Thu, Feb 14, 2019 at 11:16:09AM +0000, Sudeep Holla wrote: > > On Wed, Feb 13, 2019 at 11:17:47PM +0100, Rafael J. Wysocki wrote: > > > On Wed, Feb 13, 2019 at 1:01 PM Sudeep Holla <sudeep.holla@arm.com> wrote: > > [...] > > > > > 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 */ > > > > > > Is this really about sysfs? > > > > > > > Nope, copy-paste from dpm_sysfs_add, will drop it. > > > > > > + if (device_pm_not_required(dev)) > > > > > > Should power.disable_depth be bumped up here or while setting the "no PM" flag? > > > > > > > OK, I missed that. > > > > Looking at it, > 1. We can't set it when we set "no PM" flag as pm_runtime_init called later > initialise it to 1 > 2. We can bump it here, but I see it's usage self contained in runtime.c > and may look odd to access it here. > > More basic question is should we really need to bump it to 2 as its > initialised to 1 in runtime_init. Right, I thought about that. Let's leave it as is maybe. :-)
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;
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 <gregkh@linuxfoundation.org> Cc: "Rafael J. Wysocki" <rafael@kernel.org> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com> --- 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 -- 2.17.1