| Message ID | 20200707171457.31540-1-daniel.lezcano@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | [RFC] powercap/drivers/energy_model: protocode: Add powercap energy model based | expand |
Hi Daniel, On Tue, Jul 7, 2020 at 10:45 PM Daniel Lezcano <daniel.lezcano@linaro.org> wrote: > > On the embedded world, the complexity of the SoC leads to an > increasing number of hotspots which need to be monitored and mitigated > as a whole in order to prevent the temperature to go above the > normative and legally stated 'skin temperature'. > > Another aspect is to sustain the performance for a given power budget, > for example virtual reality where the user can feel dizziness if the > GPU performance is capped while a big CPU is processing something > else. Or reduce the battery charging because the dissipated power is > too high compared with the power consumed by other devices. > > Nowadays, the current thermal daemons are abusing the thermal > framework cooling device state to force a specific and arbitraty state typo: arbitrary > without taking care of the governor decisions. Given the closed loop > of some governors that can confuse the logic or directly enter in > a decision conflict. > > As the number of cooling device support is limited today to the CPU > and the GPU, the thermal daemons have little control on the power > dissipation of the system. The out of tree solutions are hacking > around here and there in the drivers, in the frameworks to have > control on the devices. > > The recent introduction of the energy model allows to get power > information related to a gpu or a cpu device with a limited support. > > Thanks of the current work of Lukasz Luba: > > https://lkml.org/lkml/2020/5/27/406 > > The energy model is now being improved to be generic and extended to > all devices, so giving the opportunity to SoC vendor to define the > device energy model. > > On the other side, the powercap infrastructure is a perfect fit to define > power constraints in a hierarchical way. > > The proposal is to use the powercap framework with the energy model in > order to create a hierarchy of constraints the SoC vendor is able to > define and assign a power budget on some nodes to cap the power. > > Example of constraints hierarchy: > > Soc > | > |-- gpu > | > `-- package > | > |-- perfdomain0 > | | > | |-- cpu0 > | | > | |-- cpu1 > | | > | |-- cpu2 > | | > | `-- cpu3 > | > `-- perfdomain1 > | > |-- cpu4 > | > `-- cpu5 > > The leaves of the tree are the real devices, the intermediate nodes > are virtual, aggregating the children constraints and power Consider rephrasing as: aggregating the constraints and power characteristics of their children. > characteristics. > > For example: cpu[0-3] have 179mW max, 'perfdomain0' has 716mW max, > cpu[4-5] have 1130mw max each, 'perfordomain1' has 2260mW. It results > 'package' has 2260 + 716 = 2976mW max. > > Each node have a weight on a 2^10 basis, in order to reflect the Consider rephrasing as: node has a weight on a scale of 0 to 1024 > percentage of power distribution of the children's node. This > percentage is used to dispatch the power limit to the children. > > For example: package has 2976mW max, the weigths for the children are: typo: weights > > perfdomain0: (716 * 1024) / 2976 = 246 > perfdomain1: (2260 * 1024) / 2976 = 778 > > If we want to apply a power limit constraint of 1500mW at the package > level, the power limit will be distributed along the children as: > > perfdomain0: (1500 * 246) / 1024 = 360mW > perfdomain1: (1500 * 778) / 1024 = 1140mW > > This simple approach allows to do a fair distribution of the power > limit but it will be replaced by a more complex mechanism where the > power limit will be dynamically adjusted depending on the power > consumption of the different devices. This is an algorithm with auto > power balancing with unused power. When an allocated power budget is > not used by a device, the siblings can share this free power until the > device needs more power. > > The algorithm was presented during the ELC: > > https://ossna2020.sched.com/event/c3Wf/ideas-for-finer-grained-control-over-your-heat-budget-amit-kucheria-daniel-lezcano-linaro > > Given the complexity of the code, it sounds reasonable to provide a > first stone of the edifice allowing at least the thermal daemons to > stop abusing the thermal framework where the primary goal is to > protect the silicone, not cap the power. typo: silicon > > However, one question remains: how do we describe the hierarchy? > Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> > --- > drivers/powercap/Kconfig | 8 + > drivers/powercap/Makefile | 1 + > drivers/powercap/powercap_em.c | 485 +++++++++++++++++++++++++++++++++ > include/linux/cpuhotplug.h | 1 + > 4 files changed, 495 insertions(+) > create mode 100644 drivers/powercap/powercap_em.c > > diff --git a/drivers/powercap/Kconfig b/drivers/powercap/Kconfig > index ebc4d4578339..57f2e9f31560 100644 > --- a/drivers/powercap/Kconfig > +++ b/drivers/powercap/Kconfig > @@ -43,4 +43,12 @@ config IDLE_INJECT > CPUs for power capping. Idle period can be injected > synchronously on a set of specified CPUs or alternatively > on a per CPU basis. > + > +config POWERCAP_EM > + bool "Energy model based power capping" > + depends on ENERGY_MODEL > + default y Don't make it default ;-) > + help > + This enables support for the power capping using the energy > + model and the associated per device performance state. > endif > diff --git a/drivers/powercap/Makefile b/drivers/powercap/Makefile > index 7255c94ec61c..d9fa1255a499 100644 > --- a/drivers/powercap/Makefile > +++ b/drivers/powercap/Makefile > @@ -1,5 +1,6 @@ > # SPDX-License-Identifier: GPL-2.0-only > obj-$(CONFIG_POWERCAP) += powercap_sys.o > +obj-$(CONFIG_POWERCAP_EM) += powercap_em.o > obj-$(CONFIG_INTEL_RAPL_CORE) += intel_rapl_common.o > obj-$(CONFIG_INTEL_RAPL) += intel_rapl_msr.o > obj-$(CONFIG_IDLE_INJECT) += idle_inject.o > diff --git a/drivers/powercap/powercap_em.c b/drivers/powercap/powercap_em.c > new file mode 100644 > index 000000000000..a5252d32c4e9 > --- /dev/null > +++ b/drivers/powercap/powercap_em.c > @@ -0,0 +1,485 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* > + * Copyright 2020 Linaro Limited > + * > + * Author: Daniel Lezcano <daniel.lezcano@linaro.org> > + * > + */ > +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt > + > +#include <linux/cpumask.h> > +#include <linux/cpufreq.h> > +#include <linux/cpuhotplug.h> > +#include <linux/device.h> > +#include <linux/energy_model.h> > +#include <linux/hrtimer.h> > +#include <linux/init.h> > +#include <linux/kernel.h> > +#include <linux/module.h> > +#include <linux/pm_qos.h> > +#include <linux/powercap.h> > +#include <linux/slab.h> > +#include <linux/spinlock.h> > +#include <linux/sysfs.h> > +#include <linux/units.h> > + > +struct powercap_em { > + struct powercap_zone zone; > + struct powercap_em *parent; > + struct list_head sibling; > + struct list_head children; > + struct freq_qos_request qos_req; > + spinlock_t lock; > + bool mode; > + u64 power_limit; > + u64 power_max; > + u64 power_min; > + int weight; > + int cpu; > +}; > + > +static const char *constraint_name[] = { > + "Performance capping", > +}; > + > +static struct powercap_control_type *pct; > +static struct powercap_em *pc_soc; > +static struct powercap_em *pc_package; > + > +struct powercap_em *to_powercap_em(struct powercap_zone *zone) > +{ > + return container_of(zone, struct powercap_em, zone); > +} > + > +/* > + * Browse the powercap nodes of the tree and rebalance their > + * weigths. This function is called when a node is inserted or > + * deleted. > + */ > +static void powercap_em_rebalance_weight(struct powercap_em *pcem) > +{ > + struct powercap_em *child; > + > + spin_lock(&pcem->lock); > + list_for_each_entry(child, &pcem->children, sibling) { > + > + child->weight = (child->power_max * 1024) / pcem->power_max; > + > + powercap_em_rebalance_weight(child); > + } > + spin_unlock(&pcem->lock); > +} > + > +/* > + * Initialize the energy model powercap zone by calling the underlying > + * powercap register function followed by the specific allocations. > + */ > +static struct powercap_em * > +powercap_em_register(struct powercap_control_type *control_type, > + const char *name, > + struct powercap_em *parent, > + const struct powercap_zone_ops *ops, > + int nr_constraints, > + const struct powercap_zone_constraint_ops *const_ops) > +{ > + struct powercap_em *pcem; > + struct powercap_zone *pcz; > + > + pcem = kzalloc(sizeof(*pcem), GFP_KERNEL); > + if (!pcem) > + return NULL; > + > + INIT_LIST_HEAD(&pcem->children); > + INIT_LIST_HEAD(&pcem->sibling); > + spin_lock_init(&pcem->lock); > + > + pcz = powercap_register_zone(&pcem->zone, control_type, name, > + parent ? &parent->zone : NULL, > + ops, nr_constraints, const_ops); > + if (IS_ERR(pcz)) { > + kfree(pcem); > + return NULL; > + } > + > + /* > + * The root node does not have a parent > + */ > + if (parent) { > + spin_lock(&parent->lock); > + list_add_tail(&pcem->sibling, &parent->children); > + spin_unlock(&parent->lock); > + pcem->parent = parent; > + } > + > + return pcem; > +} > + Move this function closer to where it is called? > +/* > + * When a new powercap zone is inserted, propagate its power numbers > + * to the parents. > + */ > +static int powercap_em_set_power_range(struct powercap_em *pcem, > + struct em_perf_domain *em) > +{ > + struct powercap_em *parent = pcem->parent; > + int nr_cpus = cpumask_weight(to_cpumask(em->cpus)); > + > + if (pcem->power_min || pcem->power_max) > + return -EINVAL; > + > + pcem->power_min = em->table[0].power; > + pcem->power_min *= MICROWATT_PER_MILLIWATT; This is undefined. > + pcem->power_min *= nr_cpus; > + > + pcem->power_max = em->table[em->nr_cap_states - 1].power; s/nr_cap_states/nr_perf_states as per changes done by Lukasz. > + pcem->power_max *= MICROWATT_PER_MILLIWATT; > + pcem->power_max *= nr_cpus; > + > + while (parent) { > + spin_lock(&parent->lock); > + parent->power_min += pcem->power_min; > + parent->power_max += pcem->power_max; > + spin_unlock(&parent->lock); > + parent = parent->parent; > + } > + > + return 0; > +} > + > +static int get_max_power_range_uw(struct powercap_zone *pcz, u64 *max_power_uw) > +{ > + struct powercap_em *pcem = to_powercap_em(pcz); > + > + spin_lock(&pcem->lock); > + *max_power_uw = pcem->power_max; > + spin_unlock(&pcem->lock); > + > + return 0; > +} > + > +static int get_pd_power_uw(struct powercap_zone *pcz, u64 *power_uw) > +{ > + struct powercap_em *pcem = to_powercap_em(pcz); > + struct em_perf_domain *pd; > + unsigned long freq; > + int i, nr_cpus; > + > + freq = cpufreq_quick_get(pcem->cpu); > + pd = em_cpu_get(pcem->cpu); > + nr_cpus = cpumask_weight(to_cpumask(pd->cpus)); > + > + for (i = 0; i < pd->nr_cap_states; i++) { > + > + if (pd->table[i].frequency < freq) > + continue; > + > + *power_uw = pd->table[i].power * > + MICROWATT_PER_MILLIWATT * nr_cpus; > + > + return 0; > + } > + > + return -EINVAL; > +} > + > +static int get_children_power_uw(struct powercap_zone *pcz, u64 *power_uw) > +{ > + struct powercap_em *pcem = to_powercap_em(pcz); > + struct powercap_em *child; > + u64 power; > + int ret = 0; > + > + *power_uw = 0; > + > + spin_lock(&pcem->lock); > + list_for_each_entry(child, &pcem->children, sibling) { > + ret = child->zone.ops->get_power_uw(&child->zone, &power); > + if (ret) > + break; > + *power_uw += power; > + } > + spin_unlock(&pcem->lock); > + > + return ret; > +} > + > +static int set_domain_enable(struct powercap_zone *pcz, bool mode) > +{ > + struct powercap_em *pcem = to_powercap_em(pcz); > + struct cpufreq_policy *policy; > + struct em_perf_domain *pd; > + int ret; > + > + if (mode) { > + policy = cpufreq_cpu_get(pcem->cpu); > + if (!policy) > + return -EINVAL; > + > + pd = em_cpu_get(pcem->cpu); > + if (!pd) > + return -EINVAL; > + > + ret = freq_qos_add_request(&policy->constraints, > + &pcem->qos_req, FREQ_QOS_MAX, > + pd->table[pd->nr_cap_states - 1].frequency); > + if (ret) > + return ret; > + > + } else { > + freq_qos_remove_request(&pcem->qos_req); > + } > + > + pcem->mode = mode; > + > + powercap_em_rebalance_weight(pc_soc); > + > + return 0; > +} > + > +static int get_domain_enable(struct powercap_zone *pcz, bool *mode) > +{ > + struct powercap_em *pcem = to_powercap_em(pcz); > + > + *mode = pcem->mode; > + > + return 0; > +} > + > +static int release_zone(struct powercap_zone *pcz) > +{ > + struct powercap_em *pcem = to_powercap_em(pcz); > + > + if (!list_empty(&pcem->children)) > + return -EBUSY; > + > + freq_qos_remove_request(&pcem->qos_req); > + list_del(&pcem->sibling); > + kfree(pcem); > + powercap_em_rebalance_weight(pc_soc); > + > + return 0; > +} > + > +/* > + * Set the power limit on the nodes, the power limit is distributed > + * given the weight of the children. > + */ > +static int set_children_power_limit(struct powercap_zone *pcz, int cid, > + u64 power_limit) > +{ > + struct powercap_em *pcem = to_powercap_em(pcz); > + struct powercap_em *child; > + u64 power; > + int ret = 0; > + > + /* > + * Don't allow values outside of the power range previously > + * set when initiliazing the powercap energy model zone > + */ > + pcem->power_limit = clamp_val(power_limit, > + pcem->power_min, > + pcem->power_max); > + > + spin_lock(&pcem->lock); > + list_for_each_entry(child, &pcem->children, sibling) { > + > + power = (pcem->power_limit * child->weight) / 1024; > + > + ret = child->zone.constraints->ops->set_power_limit_uw( > + &child->zone, cid, power); > + if (ret) > + break; > + } > + spin_unlock(&pcem->lock); > + > + > + return ret; > +} > + > +static int get_children_power_limit(struct powercap_zone *pcz, int cid, u64 *data) > +{ > + struct powercap_em *pcem = to_powercap_em(pcz); > + struct powercap_em *child; > + u64 power; > + int ret = 0; > + > + *data = 0; > + > + spin_lock(&pcem->lock); > + list_for_each_entry(child, &pcem->children, sibling) { > + ret = child->zone.constraints->ops->get_power_limit_uw( > + &child->zone, cid, &power); > + if (ret) > + break; > + *data += power; > + } > + spin_unlock(&pcem->lock); > + > + return ret; > +} > + > +static const char *get_constraint_name(struct powercap_zone *pcz, int cid) > +{ > + return constraint_name[cid]; > +} > + > +static int set_pd_power_limit(struct powercap_zone *pcz, int cid, > + u64 power_limit) > +{ > + struct powercap_em *pcem = to_powercap_em(pcz); > + struct em_perf_domain *pd; > + unsigned long frequency; > + int i, nr_cpus; > + > + spin_lock(&pcem->lock); > + > + power_limit = clamp_val(power_limit, pcem->power_min, pcem->power_max); > + > + pd = em_cpu_get(pcem->cpu); > + > + nr_cpus = cpumask_weight(to_cpumask(pd->cpus)); > + > + for (i = 0, frequency = pd->table[0].frequency; i < pd->nr_cap_states; i++) { > + > + u64 power = pd->table[i].power * MICROWATT_PER_MILLIWATT; > + > + if ((power * nr_cpus) > power_limit) > + break; > + > + frequency = pd->table[i].frequency; > + } > + > + freq_qos_update_request(&pcem->qos_req, frequency); > + > + pcem->power_limit = power_limit; > + > + spin_unlock(&pcem->lock); > + > + return 0; > +} > + > +static int get_pd_power_limit(struct powercap_zone *pcz, int cid, u64 *data) > +{ > + struct powercap_em *pcem = to_powercap_em(pcz); > + > + spin_lock(&pcem->lock); > + *data = pcem->power_limit ? pcem->power_limit : pcem->power_max; > + spin_unlock(&pcem->lock); > + > + return 0; > +} > + > +static int set_time_window(struct powercap_zone *pcz, int cid, u64 window) > +{ > + return -ENOSYS; > +} > + > + > +static int get_time_window(struct powercap_zone *pcz, int cid, u64 *data) > +{ > + *data = 0; > + > + return 0; > +} > + > +static int get_max_power_uw(struct powercap_zone *pcz, int id, u64 *data) > +{ > + return get_max_power_range_uw(pcz, data); > +} > + > +static const struct powercap_zone_constraint_ops constraint_ops = { > + .set_power_limit_uw = set_children_power_limit, > + .get_power_limit_uw = get_children_power_limit, > + .set_time_window_us = set_time_window, > + .get_time_window_us = get_time_window, > + .get_max_power_uw = get_max_power_uw, > + .get_name = get_constraint_name, > +}; > + > +static const struct powercap_zone_constraint_ops pd_constraint_ops = { > + .set_power_limit_uw = set_pd_power_limit, > + .get_power_limit_uw = get_pd_power_limit, > + .set_time_window_us = set_time_window, > + .get_time_window_us = get_time_window, > + .get_max_power_uw = get_max_power_uw, > + .get_name = get_constraint_name, > +}; > + > +static const struct powercap_zone_ops zone_ops = { > + .get_max_power_range_uw = get_max_power_range_uw, > + .get_power_uw = get_children_power_uw, > + .set_enable = set_domain_enable, > + .get_enable = get_domain_enable, > + .release = release_zone, > +}; > + > +static const struct powercap_zone_ops pd_zone_ops = { > + .get_max_power_range_uw = get_max_power_range_uw, > + .get_power_uw = get_pd_power_uw, > + .set_enable = set_domain_enable, > + .get_enable = get_domain_enable, > + .release = release_zone, > +}; > + > +static int cpuhp_powercap_em_online(unsigned int cpu) > +{ > + struct powercap_em *pcem; Bad spacing > + struct cpufreq_policy *policy; > + struct em_perf_domain *pd; > + char name[CPUFREQ_NAME_LEN]; > + int ret; > + > + policy = cpufreq_cpu_get(cpu); > + > + if (!policy || cpumask_first(policy->related_cpus) != cpu) > + return 0; > + > + pd = em_cpu_get(cpu); > + if (!pd) > + return -EINVAL; > + > + sprintf(name, "policy%d", cpu); > + > + pcem = powercap_em_register(pct, name, pc_package, > + &pd_zone_ops, 1, &pd_constraint_ops); > + if (!pcem) > + return -EINVAL; > + > + ret = powercap_em_set_power_range(pcem, pd); > + if (ret) > + return ret; > + > + pcem->cpu = cpu; > + > + ret = freq_qos_add_request(&policy->constraints, > + &pcem->qos_req, FREQ_QOS_MAX, > + pd->table[pd->nr_cap_states - 1].frequency); > + > + powercap_em_rebalance_weight(pc_soc); > + > + return ret; > +} > + > +static int __init powercap_em_init(void) > +{ > + pct = powercap_register_control_type(NULL, "energy_model", NULL); > + if (!pct) { > + pr_err("Failed to register control type\n"); > + return -EINVAL; Return PTR_ERR(pct) here since powercap_register_control_type returns at least three types of errors. > + } > + > + pc_soc = powercap_em_register(pct, "soc", NULL, Please consider moving powercap_em_register() just above this function. > + &zone_ops, 1, &constraint_ops); > + if (!pc_soc) > + return -EINVAL; > + > + pc_package = powercap_em_register(pct, "package", pc_soc, > + &zone_ops, 1, &constraint_ops); Will the soc and package hierarchy eventually be dynamically read from devicetree or similar and these hardcoded registration removed? For the rest of the devices, IMO, it makes sense to use the genpd hierarchy to reflect the powercap hierarchy. I whipped up the following patch to show how it might be achieved. What needs to be done is to now reflect the parent-child/sibling relationships of genpd into powercap. Initially I thought we'd need to additional DT properties in the genpd bindings but I think we might be able to read the device-specific energy model data directly to populate the powercap constraints. Thundercomm_Dragonboard_845c / $ ll /sys/class/powercap/ total 0 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model -> ../../devices/virtual/powercap/energy_model lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:0 -> ../../devices/virtual/powercap/energy_model/energy_model:0 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:0:0 -> ../../devices/virtual/powercap/energy_model/energy_model:0/energy_model:0:0 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:0:0:0 -> ../../devices/virtual/powercap/energy_model/energy_model:0/energy_model:0:0/energy_model:0:0:0 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:0:0:1 -> ../../devices/virtual/powercap/energy_model/energy_model:0/energy_model:0:0/energy_model:0:0:1 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:1 -> ../../devices/virtual/powercap/energy_model/energy_model:1 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:10 -> ../../devices/virtual/powercap/energy_model/energy_model:10 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:11 -> ../../devices/virtual/powercap/energy_model/energy_model:11 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:12 -> ../../devices/virtual/powercap/energy_model/energy_model:12 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:13 -> ../../devices/virtual/powercap/energy_model/energy_model:13 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:14 -> ../../devices/virtual/powercap/energy_model/energy_model:14 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:15 -> ../../devices/virtual/powercap/energy_model/energy_model:15 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:16 -> ../../devices/virtual/powercap/energy_model/energy_model:16 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:17 -> ../../devices/virtual/powercap/energy_model/energy_model:17 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:18 -> ../../devices/virtual/powercap/energy_model/energy_model:18 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:19 -> ../../devices/virtual/powercap/energy_model/energy_model:19 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:1a -> ../../devices/virtual/powercap/energy_model/energy_model:1a lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:1b -> ../../devices/virtual/powercap/energy_model/energy_model:1b lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:1c -> ../../devices/virtual/powercap/energy_model/energy_model:1c lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:1d -> ../../devices/virtual/powercap/energy_model/energy_model:1d lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:1e -> ../../devices/virtual/powercap/energy_model/energy_model:1e lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:1f -> ../../devices/virtual/powercap/energy_model/energy_model:1f lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:2 -> ../../devices/virtual/powercap/energy_model/energy_model:2 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:20 -> ../../devices/virtual/powercap/energy_model/energy_model:20 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:21 -> ../../devices/virtual/powercap/energy_model/energy_model:21 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:22 -> ../../devices/virtual/powercap/energy_model/energy_model:22 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:3 -> ../../devices/virtual/powercap/energy_model/energy_model:3 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:4 -> ../../devices/virtual/powercap/energy_model/energy_model:4 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:5 -> ../../devices/virtual/powercap/energy_model/energy_model:5 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:6 -> ../../devices/virtual/powercap/energy_model/energy_model:6 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:7 -> ../../devices/virtual/powercap/energy_model/energy_model:7 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:8 -> ../../devices/virtual/powercap/energy_model/energy_model:8 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:9 -> ../../devices/virtual/powercap/energy_model/energy_model:9 lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:a -> ../../devices/virtual/powercap/energy_model/energy_model:a lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:b -> ../../devices/virtual/powercap/energy_model/energy_model:b lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:c -> ../../devices/virtual/powercap/energy_model/energy_model:c lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:d -> ../../devices/virtual/powercap/energy_model/energy_model:d lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:e -> ../../devices/virtual/powercap/energy_model/energy_model:e lrwxrwxrwx 1 root root 0 Jan 1 00:00 energy_model:f -> ../../devices/virtual/powercap/energy_model/energy_model:f Let me know what you think. Regards, Amit > + if (!pc_package) > + return -EINVAL; > + > + return cpuhp_setup_state(CPUHP_AP_POWERCAP_EM_ONLINE, > + "powercap_em:online", > + cpuhp_powercap_em_online, NULL); > +} > +late_initcall(powercap_em_init); > diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h > index 191772d4a4d7..09fe4e1b430e 100644 > --- a/include/linux/cpuhotplug.h > +++ b/include/linux/cpuhotplug.h > @@ -189,6 +189,7 @@ enum cpuhp_state { > CPUHP_AP_ONLINE_DYN_END = CPUHP_AP_ONLINE_DYN + 30, > CPUHP_AP_X86_HPET_ONLINE, > CPUHP_AP_X86_KVM_CLK_ONLINE, > + CPUHP_AP_POWERCAP_EM_ONLINE, > CPUHP_AP_ACTIVE, > CPUHP_ONLINE, > }; > -- > 2.17.1 > From ef513af4af3ca6ad664155e6f4908cf720d6afb6 Mon Sep 17 00:00:00 2001 Message-Id: <ef513af4af3ca6ad664155e6f4908cf720d6afb6.1599730904.git.amitk@kernel.org> From: Amit Kucheria <amitk@kernel.org> Date: Thu, 10 Sep 2020 15:02:21 +0530 Subject: [PATCH] powercap_em: automatic registration of powercap em zones based on genpd genpd already captures the physical and virtual hierarchy of how blocks in an SoC are powered and their various dependencies. Use that to create an equivalent powercap hierarchy. FIXME: This is proof-of-concept that doesn't take in to account child and sibling relationships in genpd. Currently, all powercap zones are created at the root level. This needs to be fixed. FIXME #2: The energy costing for devices could be looked up from the energy model during init to fill up the constraint table. FIXME #3: Revisit if there is a need for a separate property inside genpd DT bindings to powercap. Signed-off-by: Amit Kucheria <amitk@kernel.org> --- drivers/base/power/domain.c | 4 ++-- drivers/powercap/powercap_em.c | 19 +++++++++++++++++++ include/linux/powercap.h | 3 +++ 3 files changed, 24 insertions(+), 2 deletions(-) diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c index 2cb5e04cf86cd..f81a7c4060b65 100644 --- a/drivers/base/power/domain.c +++ b/drivers/base/power/domain.c @@ -38,8 +38,8 @@ __ret; \ }) -static LIST_HEAD(gpd_list); -static DEFINE_MUTEX(gpd_list_lock); +LIST_HEAD(gpd_list); +DEFINE_MUTEX(gpd_list_lock); struct genpd_lock_ops { void (*lock)(struct generic_pm_domain *genpd); diff --git a/drivers/powercap/powercap_em.c b/drivers/powercap/powercap_em.c index 725d604330c70..c616f7f3bce08 100644 --- a/drivers/powercap/powercap_em.c +++ b/drivers/powercap/powercap_em.c @@ -18,6 +18,7 @@ #include <linux/init.h> #include <linux/kernel.h> #include <linux/module.h> +#include <linux/pm_domain.h> #include <linux/pm_qos.h> #include <linux/powercap.h> #include <linux/slab.h> @@ -464,6 +465,9 @@ static int cpuhp_powercap_em_online(unsigned int cpu) static int __init powercap_em_init(void) { + struct generic_pm_domain *genpd; + struct powercap_em *pc_dev; + pct = powercap_register_control_type(NULL, "energy_model", NULL); if (!pct) { pr_err("Failed to register control type\n"); @@ -480,6 +484,21 @@ static int __init powercap_em_init(void) if (!pc_package) return -EINVAL; + mutex_lock(&gpd_list_lock); + + list_for_each_entry(genpd, &gpd_list, gpd_list_node) { + dev_err(&genpd->dev, "registering powercap em zone"); + pc_dev = powercap_em_register(pct, dev_name(&genpd->dev), NULL, + &zone_ops, 1, &constraint_ops); + + if (!pc_dev) { + dev_err(&genpd->dev, "error registering powercap em zone"); + } + } + + mutex_unlock(&gpd_list_lock); + + return cpuhp_setup_state(CPUHP_AP_POWERCAP_EM_ONLINE, "powercap_em:online", cpuhp_powercap_em_online, NULL); diff --git a/include/linux/powercap.h b/include/linux/powercap.h index babf10261744f..943ddc108d663 100644 --- a/include/linux/powercap.h +++ b/include/linux/powercap.h @@ -20,6 +20,9 @@ struct powercap_control_type; struct powercap_zone; struct powercap_zone_constraint; +extern struct list_head gpd_list; +extern struct mutex gpd_list_lock; + /** * struct powercap_control_type_ops - Define control type callbacks * @set_enable: Enable/Disable whole control type.
Hi Amit, thanks for taking the time to review the series and read this long description. On 10/09/2020 11:48, Amit Kucheria wrote: [ ... ] >> + >> +config POWERCAP_EM >> + bool "Energy model based power capping" >> + depends on ENERGY_MODEL >> + default y > > Don't make it default ;-) Thanks for pointing this out :D [ ... ] >> + pc_package = powercap_em_register(pct, "package", pc_soc, >> + &zone_ops, 1, &constraint_ops); > > Will the soc and package hierarchy eventually be dynamically read from > devicetree or similar and these hardcoded registration removed? Yes, that's correct. > For the rest of the devices, IMO, it makes sense to use the genpd > hierarchy to reflect the powercap hierarchy. I whipped up the > following patch to show how it might be achieved. What needs to be > done is to now reflect the parent-child/sibling relationships of genpd > into powercap. Initially I thought we'd need to additional DT > properties in the genpd bindings but I think we might be able to read > the device-specific energy model data directly to populate the > powercap constraints. We need a way to describe the power constraints relationship of the domains to populate the hierarchy of the powercap directories. In the DT it may look like that (very roughly): power-constraints { power-constraint: package { compatible = "power-constraint,virtual"; }; power-constraint: perfdomain0 { compatible = "power-constraint,cpu"; device = <&cpu_l0>; parent = <&package>; }; power-constraint: perfdomain1 { compatible = "power-constraint,cpu"; device = <&cpu_b0>; parent = <&package>; }; power-constraint: gpu { compatible = "power-constraint,gpu"; parent = <&package> }; }; -- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog
diff --git a/drivers/powercap/Kconfig b/drivers/powercap/Kconfig index ebc4d4578339..57f2e9f31560 100644 --- a/drivers/powercap/Kconfig +++ b/drivers/powercap/Kconfig @@ -43,4 +43,12 @@ config IDLE_INJECT CPUs for power capping. Idle period can be injected synchronously on a set of specified CPUs or alternatively on a per CPU basis. + +config POWERCAP_EM + bool "Energy model based power capping" + depends on ENERGY_MODEL + default y + help + This enables support for the power capping using the energy + model and the associated per device performance state. endif diff --git a/drivers/powercap/Makefile b/drivers/powercap/Makefile index 7255c94ec61c..d9fa1255a499 100644 --- a/drivers/powercap/Makefile +++ b/drivers/powercap/Makefile @@ -1,5 +1,6 @@ # SPDX-License-Identifier: GPL-2.0-only obj-$(CONFIG_POWERCAP) += powercap_sys.o +obj-$(CONFIG_POWERCAP_EM) += powercap_em.o obj-$(CONFIG_INTEL_RAPL_CORE) += intel_rapl_common.o obj-$(CONFIG_INTEL_RAPL) += intel_rapl_msr.o obj-$(CONFIG_IDLE_INJECT) += idle_inject.o diff --git a/drivers/powercap/powercap_em.c b/drivers/powercap/powercap_em.c new file mode 100644 index 000000000000..a5252d32c4e9 --- /dev/null +++ b/drivers/powercap/powercap_em.c @@ -0,0 +1,485 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright 2020 Linaro Limited + * + * Author: Daniel Lezcano <daniel.lezcano@linaro.org> + * + */ +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/cpumask.h> +#include <linux/cpufreq.h> +#include <linux/cpuhotplug.h> +#include <linux/device.h> +#include <linux/energy_model.h> +#include <linux/hrtimer.h> +#include <linux/init.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/pm_qos.h> +#include <linux/powercap.h> +#include <linux/slab.h> +#include <linux/spinlock.h> +#include <linux/sysfs.h> +#include <linux/units.h> + +struct powercap_em { + struct powercap_zone zone; + struct powercap_em *parent; + struct list_head sibling; + struct list_head children; + struct freq_qos_request qos_req; + spinlock_t lock; + bool mode; + u64 power_limit; + u64 power_max; + u64 power_min; + int weight; + int cpu; +}; + +static const char *constraint_name[] = { + "Performance capping", +}; + +static struct powercap_control_type *pct; +static struct powercap_em *pc_soc; +static struct powercap_em *pc_package; + +struct powercap_em *to_powercap_em(struct powercap_zone *zone) +{ + return container_of(zone, struct powercap_em, zone); +} + +/* + * Browse the powercap nodes of the tree and rebalance their + * weigths. This function is called when a node is inserted or + * deleted. + */ +static void powercap_em_rebalance_weight(struct powercap_em *pcem) +{ + struct powercap_em *child; + + spin_lock(&pcem->lock); + list_for_each_entry(child, &pcem->children, sibling) { + + child->weight = (child->power_max * 1024) / pcem->power_max; + + powercap_em_rebalance_weight(child); + } + spin_unlock(&pcem->lock); +} + +/* + * Initialize the energy model powercap zone by calling the underlying + * powercap register function followed by the specific allocations. + */ +static struct powercap_em * +powercap_em_register(struct powercap_control_type *control_type, + const char *name, + struct powercap_em *parent, + const struct powercap_zone_ops *ops, + int nr_constraints, + const struct powercap_zone_constraint_ops *const_ops) +{ + struct powercap_em *pcem; + struct powercap_zone *pcz; + + pcem = kzalloc(sizeof(*pcem), GFP_KERNEL); + if (!pcem) + return NULL; + + INIT_LIST_HEAD(&pcem->children); + INIT_LIST_HEAD(&pcem->sibling); + spin_lock_init(&pcem->lock); + + pcz = powercap_register_zone(&pcem->zone, control_type, name, + parent ? &parent->zone : NULL, + ops, nr_constraints, const_ops); + if (IS_ERR(pcz)) { + kfree(pcem); + return NULL; + } + + /* + * The root node does not have a parent + */ + if (parent) { + spin_lock(&parent->lock); + list_add_tail(&pcem->sibling, &parent->children); + spin_unlock(&parent->lock); + pcem->parent = parent; + } + + return pcem; +} + +/* + * When a new powercap zone is inserted, propagate its power numbers + * to the parents. + */ +static int powercap_em_set_power_range(struct powercap_em *pcem, + struct em_perf_domain *em) +{ + struct powercap_em *parent = pcem->parent; + int nr_cpus = cpumask_weight(to_cpumask(em->cpus)); + + if (pcem->power_min || pcem->power_max) + return -EINVAL; + + pcem->power_min = em->table[0].power; + pcem->power_min *= MICROWATT_PER_MILLIWATT; + pcem->power_min *= nr_cpus; + + pcem->power_max = em->table[em->nr_cap_states - 1].power; + pcem->power_max *= MICROWATT_PER_MILLIWATT; + pcem->power_max *= nr_cpus; + + while (parent) { + spin_lock(&parent->lock); + parent->power_min += pcem->power_min; + parent->power_max += pcem->power_max; + spin_unlock(&parent->lock); + parent = parent->parent; + } + + return 0; +} + +static int get_max_power_range_uw(struct powercap_zone *pcz, u64 *max_power_uw) +{ + struct powercap_em *pcem = to_powercap_em(pcz); + + spin_lock(&pcem->lock); + *max_power_uw = pcem->power_max; + spin_unlock(&pcem->lock); + + return 0; +} + +static int get_pd_power_uw(struct powercap_zone *pcz, u64 *power_uw) +{ + struct powercap_em *pcem = to_powercap_em(pcz); + struct em_perf_domain *pd; + unsigned long freq; + int i, nr_cpus; + + freq = cpufreq_quick_get(pcem->cpu); + pd = em_cpu_get(pcem->cpu); + nr_cpus = cpumask_weight(to_cpumask(pd->cpus)); + + for (i = 0; i < pd->nr_cap_states; i++) { + + if (pd->table[i].frequency < freq) + continue; + + *power_uw = pd->table[i].power * + MICROWATT_PER_MILLIWATT * nr_cpus; + + return 0; + } + + return -EINVAL; +} + +static int get_children_power_uw(struct powercap_zone *pcz, u64 *power_uw) +{ + struct powercap_em *pcem = to_powercap_em(pcz); + struct powercap_em *child; + u64 power; + int ret = 0; + + *power_uw = 0; + + spin_lock(&pcem->lock); + list_for_each_entry(child, &pcem->children, sibling) { + ret = child->zone.ops->get_power_uw(&child->zone, &power); + if (ret) + break; + *power_uw += power; + } + spin_unlock(&pcem->lock); + + return ret; +} + +static int set_domain_enable(struct powercap_zone *pcz, bool mode) +{ + struct powercap_em *pcem = to_powercap_em(pcz); + struct cpufreq_policy *policy; + struct em_perf_domain *pd; + int ret; + + if (mode) { + policy = cpufreq_cpu_get(pcem->cpu); + if (!policy) + return -EINVAL; + + pd = em_cpu_get(pcem->cpu); + if (!pd) + return -EINVAL; + + ret = freq_qos_add_request(&policy->constraints, + &pcem->qos_req, FREQ_QOS_MAX, + pd->table[pd->nr_cap_states - 1].frequency); + if (ret) + return ret; + + } else { + freq_qos_remove_request(&pcem->qos_req); + } + + pcem->mode = mode; + + powercap_em_rebalance_weight(pc_soc); + + return 0; +} + +static int get_domain_enable(struct powercap_zone *pcz, bool *mode) +{ + struct powercap_em *pcem = to_powercap_em(pcz); + + *mode = pcem->mode; + + return 0; +} + +static int release_zone(struct powercap_zone *pcz) +{ + struct powercap_em *pcem = to_powercap_em(pcz); + + if (!list_empty(&pcem->children)) + return -EBUSY; + + freq_qos_remove_request(&pcem->qos_req); + list_del(&pcem->sibling); + kfree(pcem); + powercap_em_rebalance_weight(pc_soc); + + return 0; +} + +/* + * Set the power limit on the nodes, the power limit is distributed + * given the weight of the children. + */ +static int set_children_power_limit(struct powercap_zone *pcz, int cid, + u64 power_limit) +{ + struct powercap_em *pcem = to_powercap_em(pcz); + struct powercap_em *child; + u64 power; + int ret = 0; + + /* + * Don't allow values outside of the power range previously + * set when initiliazing the powercap energy model zone + */ + pcem->power_limit = clamp_val(power_limit, + pcem->power_min, + pcem->power_max); + + spin_lock(&pcem->lock); + list_for_each_entry(child, &pcem->children, sibling) { + + power = (pcem->power_limit * child->weight) / 1024; + + ret = child->zone.constraints->ops->set_power_limit_uw( + &child->zone, cid, power); + if (ret) + break; + } + spin_unlock(&pcem->lock); + + + return ret; +} + +static int get_children_power_limit(struct powercap_zone *pcz, int cid, u64 *data) +{ + struct powercap_em *pcem = to_powercap_em(pcz); + struct powercap_em *child; + u64 power; + int ret = 0; + + *data = 0; + + spin_lock(&pcem->lock); + list_for_each_entry(child, &pcem->children, sibling) { + ret = child->zone.constraints->ops->get_power_limit_uw( + &child->zone, cid, &power); + if (ret) + break; + *data += power; + } + spin_unlock(&pcem->lock); + + return ret; +} + +static const char *get_constraint_name(struct powercap_zone *pcz, int cid) +{ + return constraint_name[cid]; +} + +static int set_pd_power_limit(struct powercap_zone *pcz, int cid, + u64 power_limit) +{ + struct powercap_em *pcem = to_powercap_em(pcz); + struct em_perf_domain *pd; + unsigned long frequency; + int i, nr_cpus; + + spin_lock(&pcem->lock); + + power_limit = clamp_val(power_limit, pcem->power_min, pcem->power_max); + + pd = em_cpu_get(pcem->cpu); + + nr_cpus = cpumask_weight(to_cpumask(pd->cpus)); + + for (i = 0, frequency = pd->table[0].frequency; i < pd->nr_cap_states; i++) { + + u64 power = pd->table[i].power * MICROWATT_PER_MILLIWATT; + + if ((power * nr_cpus) > power_limit) + break; + + frequency = pd->table[i].frequency; + } + + freq_qos_update_request(&pcem->qos_req, frequency); + + pcem->power_limit = power_limit; + + spin_unlock(&pcem->lock); + + return 0; +} + +static int get_pd_power_limit(struct powercap_zone *pcz, int cid, u64 *data) +{ + struct powercap_em *pcem = to_powercap_em(pcz); + + spin_lock(&pcem->lock); + *data = pcem->power_limit ? pcem->power_limit : pcem->power_max; + spin_unlock(&pcem->lock); + + return 0; +} + +static int set_time_window(struct powercap_zone *pcz, int cid, u64 window) +{ + return -ENOSYS; +} + + +static int get_time_window(struct powercap_zone *pcz, int cid, u64 *data) +{ + *data = 0; + + return 0; +} + +static int get_max_power_uw(struct powercap_zone *pcz, int id, u64 *data) +{ + return get_max_power_range_uw(pcz, data); +} + +static const struct powercap_zone_constraint_ops constraint_ops = { + .set_power_limit_uw = set_children_power_limit, + .get_power_limit_uw = get_children_power_limit, + .set_time_window_us = set_time_window, + .get_time_window_us = get_time_window, + .get_max_power_uw = get_max_power_uw, + .get_name = get_constraint_name, +}; + +static const struct powercap_zone_constraint_ops pd_constraint_ops = { + .set_power_limit_uw = set_pd_power_limit, + .get_power_limit_uw = get_pd_power_limit, + .set_time_window_us = set_time_window, + .get_time_window_us = get_time_window, + .get_max_power_uw = get_max_power_uw, + .get_name = get_constraint_name, +}; + +static const struct powercap_zone_ops zone_ops = { + .get_max_power_range_uw = get_max_power_range_uw, + .get_power_uw = get_children_power_uw, + .set_enable = set_domain_enable, + .get_enable = get_domain_enable, + .release = release_zone, +}; + +static const struct powercap_zone_ops pd_zone_ops = { + .get_max_power_range_uw = get_max_power_range_uw, + .get_power_uw = get_pd_power_uw, + .set_enable = set_domain_enable, + .get_enable = get_domain_enable, + .release = release_zone, +}; + +static int cpuhp_powercap_em_online(unsigned int cpu) +{ + struct powercap_em *pcem; + struct cpufreq_policy *policy; + struct em_perf_domain *pd; + char name[CPUFREQ_NAME_LEN]; + int ret; + + policy = cpufreq_cpu_get(cpu); + + if (!policy || cpumask_first(policy->related_cpus) != cpu) + return 0; + + pd = em_cpu_get(cpu); + if (!pd) + return -EINVAL; + + sprintf(name, "policy%d", cpu); + + pcem = powercap_em_register(pct, name, pc_package, + &pd_zone_ops, 1, &pd_constraint_ops); + if (!pcem) + return -EINVAL; + + ret = powercap_em_set_power_range(pcem, pd); + if (ret) + return ret; + + pcem->cpu = cpu; + + ret = freq_qos_add_request(&policy->constraints, + &pcem->qos_req, FREQ_QOS_MAX, + pd->table[pd->nr_cap_states - 1].frequency); + + powercap_em_rebalance_weight(pc_soc); + + return ret; +} + +static int __init powercap_em_init(void) +{ + pct = powercap_register_control_type(NULL, "energy_model", NULL); + if (!pct) { + pr_err("Failed to register control type\n"); + return -EINVAL; + } + + pc_soc = powercap_em_register(pct, "soc", NULL, + &zone_ops, 1, &constraint_ops); + if (!pc_soc) + return -EINVAL; + + pc_package = powercap_em_register(pct, "package", pc_soc, + &zone_ops, 1, &constraint_ops); + if (!pc_package) + return -EINVAL; + + return cpuhp_setup_state(CPUHP_AP_POWERCAP_EM_ONLINE, + "powercap_em:online", + cpuhp_powercap_em_online, NULL); +} +late_initcall(powercap_em_init); diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h index 191772d4a4d7..09fe4e1b430e 100644 --- a/include/linux/cpuhotplug.h +++ b/include/linux/cpuhotplug.h @@ -189,6 +189,7 @@ enum cpuhp_state { CPUHP_AP_ONLINE_DYN_END = CPUHP_AP_ONLINE_DYN + 30, CPUHP_AP_X86_HPET_ONLINE, CPUHP_AP_X86_KVM_CLK_ONLINE, + CPUHP_AP_POWERCAP_EM_ONLINE, CPUHP_AP_ACTIVE, CPUHP_ONLINE, };
On the embedded world, the complexity of the SoC leads to an increasing number of hotspots which need to be monitored and mitigated as a whole in order to prevent the temperature to go above the normative and legally stated 'skin temperature'. Another aspect is to sustain the performance for a given power budget, for example virtual reality where the user can feel dizziness if the GPU performance is capped while a big CPU is processing something else. Or reduce the battery charging because the dissipated power is too high compared with the power consumed by other devices. Nowadays, the current thermal daemons are abusing the thermal framework cooling device state to force a specific and arbitraty state without taking care of the governor decisions. Given the closed loop of some governors that can confuse the logic or directly enter in a decision conflict. As the number of cooling device support is limited today to the CPU and the GPU, the thermal daemons have little control on the power dissipation of the system. The out of tree solutions are hacking around here and there in the drivers, in the frameworks to have control on the devices. The recent introduction of the energy model allows to get power information related to a gpu or a cpu device with a limited support. Thanks of the current work of Lukasz Luba: https://lkml.org/lkml/2020/5/27/406 The energy model is now being improved to be generic and extended to all devices, so giving the opportunity to SoC vendor to define the device energy model. On the other side, the powercap infrastructure is a perfect fit to define power constraints in a hierarchical way. The proposal is to use the powercap framework with the energy model in order to create a hierarchy of constraints the SoC vendor is able to define and assign a power budget on some nodes to cap the power. Example of constraints hierarchy: Soc | |-- gpu | `-- package | |-- perfdomain0 | | | |-- cpu0 | | | |-- cpu1 | | | |-- cpu2 | | | `-- cpu3 | `-- perfdomain1 | |-- cpu4 | `-- cpu5 The leaves of the tree are the real devices, the intermediate nodes are virtual, aggregating the children constraints and power characteristics. For example: cpu[0-3] have 179mW max, 'perfdomain0' has 716mW max, cpu[4-5] have 1130mw max each, 'perfordomain1' has 2260mW. It results 'package' has 2260 + 716 = 2976mW max. Each node have a weight on a 2^10 basis, in order to reflect the percentage of power distribution of the children's node. This percentage is used to dispatch the power limit to the children. For example: package has 2976mW max, the weigths for the children are: perfdomain0: (716 * 1024) / 2976 = 246 perfdomain1: (2260 * 1024) / 2976 = 778 If we want to apply a power limit constraint of 1500mW at the package level, the power limit will be distributed along the children as: perfdomain0: (1500 * 246) / 1024 = 360mW perfdomain1: (1500 * 778) / 1024 = 1140mW This simple approach allows to do a fair distribution of the power limit but it will be replaced by a more complex mechanism where the power limit will be dynamically adjusted depending on the power consumption of the different devices. This is an algorithm with auto power balancing with unused power. When an allocated power budget is not used by a device, the siblings can share this free power until the device needs more power. The algorithm was presented during the ELC: https://ossna2020.sched.com/event/c3Wf/ideas-for-finer-grained-control-over-your-heat-budget-amit-kucheria-daniel-lezcano-linaro Given the complexity of the code, it sounds reasonable to provide a first stone of the edifice allowing at least the thermal daemons to stop abusing the thermal framework where the primary goal is to protect the silicone, not cap the power. However, one question remains: how do we describe the hierarchy? Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> --- drivers/powercap/Kconfig | 8 + drivers/powercap/Makefile | 1 + drivers/powercap/powercap_em.c | 485 +++++++++++++++++++++++++++++++++ include/linux/cpuhotplug.h | 1 + 4 files changed, 495 insertions(+) create mode 100644 drivers/powercap/powercap_em.c -- 2.17.1