3000ce3c52
Replace the CPU device PM QoS used for the management of min and max
frequency constraints in cpufreq (and its users) with per-policy
frequency QoS to avoid problems with cpufreq policies covering
more then one CPU.
Namely, a cpufreq driver is registered with the subsys interface
which calls cpufreq_add_dev() for each CPU, starting from CPU0, so
currently the PM QoS notifiers are added to the first CPU in the
policy (i.e. CPU0 in the majority of cases).
In turn, when the cpufreq driver is unregistered, the subsys interface
doing that calls cpufreq_remove_dev() for each CPU, starting from CPU0,
and the PM QoS notifiers are only removed when cpufreq_remove_dev() is
called for the last CPU in the policy, say CPUx, which as a rule is
not CPU0 if the policy covers more than one CPU. Then, the PM QoS
notifiers cannot be removed, because CPUx does not have them, and
they are still there in the device PM QoS notifiers list of CPU0,
which prevents new PM QoS notifiers from being registered for CPU0
on the next attempt to register the cpufreq driver.
The same issue occurs when the first CPU in the policy goes offline
before unregistering the driver.
After this change it does not matter which CPU is the policy CPU at
the driver registration time and whether or not it is online all the
time, because the frequency QoS is per policy and not per CPU.
Fixes: 67d874c3b2 ("cpufreq: Register notifiers with the PM QoS framework")
Reported-by: Dmitry Osipenko <digetx@gmail.com>
Tested-by: Dmitry Osipenko <digetx@gmail.com>
Reported-by: Sudeep Holla <sudeep.holla@arm.com>
Tested-by: Sudeep Holla <sudeep.holla@arm.com>
Diagnosed-by: Viresh Kumar <viresh.kumar@linaro.org>
Link: https://lore.kernel.org/linux-pm/5ad2624194baa2f53acc1f1e627eb7684c577a19.1562210705.git.viresh.kumar@linaro.org/T/#md2d89e95906b8c91c15f582146173dce2e86e99f
Link: https://lore.kernel.org/linux-pm/20191017094612.6tbkwoq4harsjcqv@vireshk-i7/T/#m30d48cc23b9a80467fbaa16e30f90b3828a5a29b
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
136 lines
2.6 KiB
C
136 lines
2.6 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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#include <linux/types.h>
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#include <linux/errno.h>
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#include <linux/kernel.h>
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#include <linux/delay.h>
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#include <linux/pm_qos.h>
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#include <linux/slab.h>
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#include <linux/init.h>
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#include <linux/wait.h>
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#include <linux/cpu.h>
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#include <linux/cpufreq.h>
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#include <asm/prom.h>
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#include "windfarm.h"
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#define VERSION "0.3"
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static int clamped;
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static struct wf_control *clamp_control;
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static struct freq_qos_request qos_req;
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static unsigned int min_freq, max_freq;
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static int clamp_set(struct wf_control *ct, s32 value)
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{
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unsigned int freq;
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if (value) {
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freq = min_freq;
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printk(KERN_INFO "windfarm: Clamping CPU frequency to "
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"minimum !\n");
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} else {
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freq = max_freq;
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printk(KERN_INFO "windfarm: CPU frequency unclamped !\n");
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}
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clamped = value;
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return freq_qos_update_request(&qos_req, freq);
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}
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static int clamp_get(struct wf_control *ct, s32 *value)
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{
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*value = clamped;
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return 0;
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}
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static s32 clamp_min(struct wf_control *ct)
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{
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return 0;
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}
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static s32 clamp_max(struct wf_control *ct)
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{
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return 1;
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}
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static const struct wf_control_ops clamp_ops = {
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.set_value = clamp_set,
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.get_value = clamp_get,
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.get_min = clamp_min,
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.get_max = clamp_max,
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.owner = THIS_MODULE,
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};
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static int __init wf_cpufreq_clamp_init(void)
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{
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struct cpufreq_policy *policy;
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struct wf_control *clamp;
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struct device *dev;
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int ret;
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policy = cpufreq_cpu_get(0);
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if (!policy) {
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pr_warn("%s: cpufreq policy not found cpu0\n", __func__);
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return -EPROBE_DEFER;
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}
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min_freq = policy->cpuinfo.min_freq;
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max_freq = policy->cpuinfo.max_freq;
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ret = freq_qos_add_request(&policy->constraints, &qos_req, FREQ_QOS_MAX,
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max_freq);
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cpufreq_cpu_put(policy);
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if (ret < 0) {
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pr_err("%s: Failed to add freq constraint (%d)\n", __func__,
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ret);
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return ret;
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}
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dev = get_cpu_device(0);
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if (unlikely(!dev)) {
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pr_warn("%s: No cpu device for cpu0\n", __func__);
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ret = -ENODEV;
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goto fail;
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}
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clamp = kmalloc(sizeof(struct wf_control), GFP_KERNEL);
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if (clamp == NULL) {
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ret = -ENOMEM;
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goto fail;
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}
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clamp->ops = &clamp_ops;
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clamp->name = "cpufreq-clamp";
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ret = wf_register_control(clamp);
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if (ret)
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goto free;
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clamp_control = clamp;
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return 0;
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free:
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kfree(clamp);
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fail:
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freq_qos_remove_request(&qos_req);
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return ret;
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}
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static void __exit wf_cpufreq_clamp_exit(void)
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{
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if (clamp_control) {
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wf_unregister_control(clamp_control);
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freq_qos_remove_request(&qos_req);
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}
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}
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module_init(wf_cpufreq_clamp_init);
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module_exit(wf_cpufreq_clamp_exit);
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MODULE_AUTHOR("Benjamin Herrenschmidt <benh@kernel.crashing.org>");
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MODULE_DESCRIPTION("CPU frequency clamp for PowerMacs thermal control");
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MODULE_LICENSE("GPL");
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