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![Krzysztof Kozlowski](/assets/img/avatar_default.png)
The runtime Power Management of CPU topology is not compatible with PREEMPT_RT: 1. Core cpuidle path disables IRQs. 2. Core cpuidle calls cpuidle-psci. 3. cpuidle-psci in __psci_enter_domain_idle_state() calls pm_runtime_put_sync_suspend() and pm_runtime_get_sync() which use spinlocks (which are sleeping on PREEMPT_RT). Deep sleep modes are not a priority of Realtime kernels because the latencies might become unpredictable. On the other hand the PSCI CPU idle power domain is a parent of other devices and power domain controllers, thus it cannot be simply skipped (e.g. on Qualcomm SM8250). Disable the idle callbacks in cpuidle-psci and mark the domain as always on. This is a trade-off between making PREEMPT_RT working and still having a proper power domain hierarchy in the system. Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org> Tested-by: Adrien Thierry <athierry@redhat.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
215 lines
4.7 KiB
C
215 lines
4.7 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* PM domains for CPUs via genpd - managed by cpuidle-psci.
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*
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* Copyright (C) 2019 Linaro Ltd.
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* Author: Ulf Hansson <ulf.hansson@linaro.org>
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*
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*/
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#define pr_fmt(fmt) "CPUidle PSCI: " fmt
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#include <linux/cpu.h>
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#include <linux/device.h>
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#include <linux/kernel.h>
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#include <linux/platform_device.h>
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#include <linux/pm_domain.h>
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#include <linux/pm_runtime.h>
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#include <linux/psci.h>
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#include <linux/slab.h>
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#include <linux/string.h>
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#include "cpuidle-psci.h"
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struct psci_pd_provider {
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struct list_head link;
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struct device_node *node;
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};
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static LIST_HEAD(psci_pd_providers);
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static bool psci_pd_allow_domain_state;
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static int psci_pd_power_off(struct generic_pm_domain *pd)
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{
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struct genpd_power_state *state = &pd->states[pd->state_idx];
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u32 *pd_state;
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if (!state->data)
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return 0;
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if (!psci_pd_allow_domain_state)
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return -EBUSY;
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/* OSI mode is enabled, set the corresponding domain state. */
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pd_state = state->data;
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psci_set_domain_state(*pd_state);
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return 0;
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}
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static int psci_pd_init(struct device_node *np, bool use_osi)
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{
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struct generic_pm_domain *pd;
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struct psci_pd_provider *pd_provider;
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struct dev_power_governor *pd_gov;
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int ret = -ENOMEM;
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pd = dt_idle_pd_alloc(np, psci_dt_parse_state_node);
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if (!pd)
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goto out;
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pd_provider = kzalloc(sizeof(*pd_provider), GFP_KERNEL);
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if (!pd_provider)
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goto free_pd;
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pd->flags |= GENPD_FLAG_IRQ_SAFE | GENPD_FLAG_CPU_DOMAIN;
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/*
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* Allow power off when OSI has been successfully enabled.
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* PREEMPT_RT is not yet ready to enter domain idle states.
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*/
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if (use_osi && !IS_ENABLED(CONFIG_PREEMPT_RT))
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pd->power_off = psci_pd_power_off;
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else
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pd->flags |= GENPD_FLAG_ALWAYS_ON;
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/* Use governor for CPU PM domains if it has some states to manage. */
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pd_gov = pd->states ? &pm_domain_cpu_gov : NULL;
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ret = pm_genpd_init(pd, pd_gov, false);
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if (ret)
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goto free_pd_prov;
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ret = of_genpd_add_provider_simple(np, pd);
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if (ret)
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goto remove_pd;
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pd_provider->node = of_node_get(np);
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list_add(&pd_provider->link, &psci_pd_providers);
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pr_debug("init PM domain %s\n", pd->name);
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return 0;
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remove_pd:
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pm_genpd_remove(pd);
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free_pd_prov:
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kfree(pd_provider);
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free_pd:
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dt_idle_pd_free(pd);
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out:
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pr_err("failed to init PM domain ret=%d %pOF\n", ret, np);
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return ret;
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}
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static void psci_pd_remove(void)
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{
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struct psci_pd_provider *pd_provider, *it;
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struct generic_pm_domain *genpd;
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list_for_each_entry_safe(pd_provider, it, &psci_pd_providers, link) {
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of_genpd_del_provider(pd_provider->node);
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genpd = of_genpd_remove_last(pd_provider->node);
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if (!IS_ERR(genpd))
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kfree(genpd);
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of_node_put(pd_provider->node);
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list_del(&pd_provider->link);
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kfree(pd_provider);
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}
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}
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static bool psci_pd_try_set_osi_mode(void)
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{
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int ret;
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if (!psci_has_osi_support())
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return false;
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ret = psci_set_osi_mode(true);
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if (ret)
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return false;
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return true;
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}
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static void psci_cpuidle_domain_sync_state(struct device *dev)
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{
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/*
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* All devices have now been attached/probed to the PM domain topology,
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* hence it's fine to allow domain states to be picked.
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*/
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psci_pd_allow_domain_state = true;
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}
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static const struct of_device_id psci_of_match[] = {
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{ .compatible = "arm,psci-1.0" },
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{}
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};
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static int psci_cpuidle_domain_probe(struct platform_device *pdev)
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{
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struct device_node *np = pdev->dev.of_node;
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struct device_node *node;
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bool use_osi;
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int ret = 0, pd_count = 0;
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if (!np)
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return -ENODEV;
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/* If OSI mode is supported, let's try to enable it. */
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use_osi = psci_pd_try_set_osi_mode();
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/*
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* Parse child nodes for the "#power-domain-cells" property and
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* initialize a genpd/genpd-of-provider pair when it's found.
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*/
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for_each_child_of_node(np, node) {
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if (!of_find_property(node, "#power-domain-cells", NULL))
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continue;
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ret = psci_pd_init(node, use_osi);
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if (ret)
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goto put_node;
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pd_count++;
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}
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/* Bail out if not using the hierarchical CPU topology. */
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if (!pd_count)
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goto no_pd;
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/* Link genpd masters/subdomains to model the CPU topology. */
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ret = dt_idle_pd_init_topology(np);
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if (ret)
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goto remove_pd;
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pr_info("Initialized CPU PM domain topology using %s mode\n",
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use_osi ? "OSI" : "PC");
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return 0;
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put_node:
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of_node_put(node);
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remove_pd:
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psci_pd_remove();
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pr_err("failed to create CPU PM domains ret=%d\n", ret);
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no_pd:
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if (use_osi)
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psci_set_osi_mode(false);
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return ret;
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}
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static struct platform_driver psci_cpuidle_domain_driver = {
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.probe = psci_cpuidle_domain_probe,
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.driver = {
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.name = "psci-cpuidle-domain",
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.of_match_table = psci_of_match,
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.sync_state = psci_cpuidle_domain_sync_state,
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},
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};
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static int __init psci_idle_init_domains(void)
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{
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return platform_driver_register(&psci_cpuidle_domain_driver);
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}
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subsys_initcall(psci_idle_init_domains);
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