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Date: Tue, 25 Aug 2020 10:16:02 -0600 From: Lina Iyer <ilina@...eaurora.org> To: Ulf Hansson <ulf.hansson@...aro.org> Cc: "Rafael J . Wysocki" <rjw@...ysocki.net>, Kevin Hilman <khilman@...nel.org>, linux-pm@...r.kernel.org, Sudeep Holla <sudeep.holla@....com>, Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>, Daniel Lezcano <daniel.lezcano@...aro.org>, Lukasz Luba <lukasz.luba@....com>, Vincent Guittot <vincent.guittot@...aro.org>, Stephen Boyd <sboyd@...nel.org>, Bjorn Andersson <bjorn.andersson@...aro.org>, Benjamin Gaignard <benjamin.gaignard@...com>, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 3/3] PM / Domains: Add support for PM domain on/off notifiers for genpd On Wed, Aug 19 2020 at 04:41 -0600, Ulf Hansson wrote: >A device may have specific HW constraints that must be obeyed to, before >its corresponding PM domain (genpd) can be powered off - and vice verse at >power on. These constraints can't be managed through the regular runtime PM >based deployment for a device, because the access pattern for it, isn't >always request based. In other words, using the runtime PM callbacks to >deal with the constraints doesn't work for these cases. > >For these reasons, let's instead add a PM domain power on/off notification >mechanism to genpd. To add/remove a notifier for a device, the device must >already have been attached to the genpd, which also means that it needs to >be a part of the PM domain topology. > >To add/remove a notifier, let's introduce two genpd specific functions: > - dev_pm_genpd_add|remove_notifier() > >Note that, to further clarify when genpd power on/off notifiers may be >used, one can compare with the existing CPU_CLUSTER_PM_ENTER|EXIT >notifiers. In the long run, the genpd power on/off notifiers should be able >to replace them, but that requires additional genpd based platform support >for the current users. > >Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org> >--- > drivers/base/power/domain.c | 130 ++++++++++++++++++++++++++++++++++-- > include/linux/pm_domain.h | 15 +++++ > 2 files changed, 141 insertions(+), 4 deletions(-) > >diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c >index 4b787e1ff188..9cb85a5e8342 100644 >--- a/drivers/base/power/domain.c >+++ b/drivers/base/power/domain.c >@@ -545,13 +545,21 @@ static int genpd_power_off(struct generic_pm_domain *genpd, bool one_dev_on, > if (!genpd->gov) > genpd->state_idx = 0; > >+ /* Notify consumers that we are about to power off. */ >+ ret = raw_notifier_call_chain(&genpd->power_notifiers, GENPD_STATE_OFF, >+ NULL); >+ if (ret) >+ return ret; >+ > /* Don't power off, if a child domain is waiting to power on. */ >- if (atomic_read(&genpd->sd_count) > 0) >- return -EBUSY; >+ if (atomic_read(&genpd->sd_count) > 0) { >+ ret = -EBUSY; >+ goto busy; >+ } > > ret = _genpd_power_off(genpd, true); > if (ret) >- return ret; >+ goto busy; > > genpd->status = GENPD_STATE_OFF; > genpd_update_accounting(genpd); >@@ -564,6 +572,9 @@ static int genpd_power_off(struct generic_pm_domain *genpd, bool one_dev_on, > } > > return 0; >+busy: >+ raw_notifier_call_chain(&genpd->power_notifiers, GENPD_STATE_ON, NULL); It would be helpful to abstract these notification related calls into functions of their own. So, for CPU PM domains, it would help to add RCU_NONIDLE() around the notifiers, allowing the callbacks to add trace functions. --Lina >+ return ret; > } > > /** >@@ -606,6 +617,9 @@ static int genpd_power_on(struct generic_pm_domain *genpd, unsigned int depth) > if (ret) > goto err; > >+ /* Inform consumers that we have powered on. */ >+ raw_notifier_call_chain(&genpd->power_notifiers, GENPD_STATE_ON, NULL); >+ > genpd->status = GENPD_STATE_ON; > genpd_update_accounting(genpd); > >@@ -948,9 +962,18 @@ static void genpd_sync_power_off(struct generic_pm_domain *genpd, bool use_lock, > > /* Choose the deepest state when suspending */ > genpd->state_idx = genpd->state_count - 1; >- if (_genpd_power_off(genpd, false)) >+ >+ /* Notify consumers that we are about to power off. */ >+ if (raw_notifier_call_chain(&genpd->power_notifiers, >+ GENPD_STATE_OFF, NULL)) > return; > >+ if (_genpd_power_off(genpd, false)) { >+ raw_notifier_call_chain(&genpd->power_notifiers, >+ GENPD_STATE_ON, NULL); >+ return; >+ } >+ > genpd->status = GENPD_STATE_OFF; > > list_for_each_entry(link, &genpd->child_links, child_node) { >@@ -998,6 +1021,9 @@ static void genpd_sync_power_on(struct generic_pm_domain *genpd, bool use_lock, > > _genpd_power_on(genpd, false); > >+ /* Inform consumers that we have powered on. */ >+ raw_notifier_call_chain(&genpd->power_notifiers, GENPD_STATE_ON, NULL); >+ > genpd->status = GENPD_STATE_ON; > } > >@@ -1593,6 +1619,101 @@ int pm_genpd_remove_device(struct device *dev) > } > EXPORT_SYMBOL_GPL(pm_genpd_remove_device); > >+/** >+ * dev_pm_genpd_add_notifier - Add a genpd power on/off notifier for @dev >+ * >+ * @dev: Device that should be associated with the notifier >+ * @nb: The notifier block to register >+ * >+ * Users may call this function to add a genpd power on/off notifier for an >+ * attached @dev. Only one notifier per device is allowed. The notifier is >+ * sent when genpd is powering on/off the PM domain. >+ * >+ * It is assumed that the user guarantee that the genpd wouldn't be detached >+ * while this routine is getting called. >+ * >+ * Returns 0 on success and negative error values on failures. >+ */ >+int dev_pm_genpd_add_notifier(struct device *dev, struct notifier_block *nb) >+{ >+ struct generic_pm_domain *genpd; >+ struct generic_pm_domain_data *gpd_data; >+ int ret; >+ >+ genpd = dev_to_genpd_safe(dev); >+ if (!genpd) >+ return -ENODEV; >+ >+ if (WARN_ON(!dev->power.subsys_data || >+ !dev->power.subsys_data->domain_data)) >+ return -EINVAL; >+ >+ gpd_data = to_gpd_data(dev->power.subsys_data->domain_data); >+ if (gpd_data->power_nb) >+ return -EEXIST; >+ >+ genpd_lock(genpd); >+ ret = raw_notifier_chain_register(&genpd->power_notifiers, nb); >+ genpd_unlock(genpd); >+ >+ if (ret) { >+ dev_warn(dev, "failed to add notifier for PM domain %s\n", >+ genpd->name); >+ return ret; >+ } >+ >+ gpd_data->power_nb = nb; >+ return 0; >+} >+EXPORT_SYMBOL_GPL(dev_pm_genpd_add_notifier); >+ >+/** >+ * dev_pm_genpd_remove_notifier - Remove a genpd power on/off notifier for @dev >+ * >+ * @dev: Device that is associated with the notifier >+ * >+ * Users may call this function to remove a genpd power on/off notifier for an >+ * attached @dev. >+ * >+ * It is assumed that the user guarantee that the genpd wouldn't be detached >+ * while this routine is getting called. >+ * >+ * Returns 0 on success and negative error values on failures. >+ */ >+int dev_pm_genpd_remove_notifier(struct device *dev) >+{ >+ struct generic_pm_domain *genpd; >+ struct generic_pm_domain_data *gpd_data; >+ int ret; >+ >+ genpd = dev_to_genpd_safe(dev); >+ if (!genpd) >+ return -ENODEV; >+ >+ if (WARN_ON(!dev->power.subsys_data || >+ !dev->power.subsys_data->domain_data)) >+ return -EINVAL; >+ >+ gpd_data = to_gpd_data(dev->power.subsys_data->domain_data); >+ if (!gpd_data->power_nb) >+ return -ENODEV; >+ >+ genpd_lock(genpd); >+ ret = raw_notifier_chain_unregister(&genpd->power_notifiers, >+ gpd_data->power_nb); >+ genpd_unlock(genpd); >+ >+ if (ret) { >+ dev_warn(dev, "failed to remove notifier for PM domain %s\n", >+ genpd->name); >+ return ret; >+ } >+ >+ gpd_data->power_nb = NULL; >+ return 0; >+} >+EXPORT_SYMBOL_GPL(dev_pm_genpd_remove_notifier); >+ > static int genpd_add_subdomain(struct generic_pm_domain *genpd, > struct generic_pm_domain *subdomain) > { >@@ -1763,6 +1884,7 @@ int pm_genpd_init(struct generic_pm_domain *genpd, > INIT_LIST_HEAD(&genpd->parent_links); > INIT_LIST_HEAD(&genpd->child_links); > INIT_LIST_HEAD(&genpd->dev_list); >+ RAW_INIT_NOTIFIER_HEAD(&genpd->power_notifiers); > genpd_lock_init(genpd); > genpd->gov = gov; > INIT_WORK(&genpd->power_off_work, genpd_power_off_work_fn); >diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h >index 66f3c5d64d81..3b2b561ce846 100644 >--- a/include/linux/pm_domain.h >+++ b/include/linux/pm_domain.h >@@ -112,6 +112,7 @@ struct generic_pm_domain { > cpumask_var_t cpus; /* A cpumask of the attached CPUs */ > int (*power_off)(struct generic_pm_domain *domain); > int (*power_on)(struct generic_pm_domain *domain); >+ struct raw_notifier_head power_notifiers; /* Power on/off notifiers */ > struct opp_table *opp_table; /* OPP table of the genpd */ > unsigned int (*opp_to_performance_state)(struct generic_pm_domain *genpd, > struct dev_pm_opp *opp); >@@ -178,6 +179,7 @@ struct generic_pm_domain_data { > struct pm_domain_data base; > struct gpd_timing_data td; > struct notifier_block nb; >+ struct notifier_block *power_nb; > int cpu; > unsigned int performance_state; > void *data; >@@ -204,6 +206,8 @@ int pm_genpd_init(struct generic_pm_domain *genpd, > struct dev_power_governor *gov, bool is_off); > int pm_genpd_remove(struct generic_pm_domain *genpd); > int dev_pm_genpd_set_performance_state(struct device *dev, unsigned int state); >+int dev_pm_genpd_add_notifier(struct device *dev, struct notifier_block *nb); >+int dev_pm_genpd_remove_notifier(struct device *dev); > > extern struct dev_power_governor simple_qos_governor; > extern struct dev_power_governor pm_domain_always_on_gov; >@@ -251,6 +255,17 @@ static inline int dev_pm_genpd_set_performance_state(struct device *dev, > return -ENOTSUPP; > } > >+static inline int dev_pm_genpd_add_notifier(struct device *dev, >+ struct notifier_block *nb) >+{ >+ return -ENOTSUPP; >+} >+ >+static inline int dev_pm_genpd_remove_notifier(struct device *dev) >+{ >+ return -ENOTSUPP; >+} >+ > #define simple_qos_governor (*(struct dev_power_governor *)(NULL)) > #define pm_domain_always_on_gov (*(struct dev_power_governor *)(NULL)) > #endif >-- >2.25.1 >
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