cpufreq: cpufreq_online 的大致流程

最新推荐文章于 2025-02-28 17:30:34 发布

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最新推荐文章于 2025-02-28 17:30:34 发布

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分类专栏： CPUFREQ 文章标签： linux

本文链接：https://blog.csdn.net/yuzaipiaofei/article/details/122862433

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本文详细介绍了Linux内核中cpufreq在线过程，包括调用cpu驱动的初始化回调函数，执行cpufreq_driver->init()进行policy初始化，以及注册thermal控制相关的回调函数，如of_cpufreq_cooling_register()用于策略设置。

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call cpu driver的init callback
ret = cpufreq_driver->init(policy)

//初始化policy并调用set_policy
ret = cpufreq_init_policy(policy);

//注册thermal 相关callback
if (cpufreq_thermal_control_enabled(cpufreq_driver))
policy->cdev = of_cpufreq_cooling_register(policy);

static int cpufreq_online(unsigned int cpu)
{
	struct cpufreq_policy *policy;
	bool new_policy;
	unsigned long flags;
	unsigned int j;
	int ret;

	pr_debug("%s: bringing CPU%u online\n", __func__, cpu);

	/* Check if this CPU already has a policy to manage it */
	policy = per_cpu(cpufreq_cpu_data, cpu);
	if (policy) {
		WARN_ON(!cpumask_test_cpu(cpu, policy->related_cpus));
		if (!policy_is_inactive(policy))
			return cpufreq_add_policy_cpu(policy, cpu);

		/* This is the only online CPU for the policy.  Start over. */
		new_policy = false;
		down_write(&policy->rwsem);
		policy->cpu = cpu;
		policy->governor = NULL;
		up_write(&policy->rwsem);
	} else {
		new_policy = true;
		policy = cpufreq_policy_alloc(cpu);
		if (!policy)
			return -ENOMEM;
	}

	if (!new_policy && cpufreq_driver->online) {
		ret = cpufreq_driver->online(policy);
		if (ret) {
			pr_debug("%s: %d: initialization failed\n", __func__,
				 __LINE__);
			goto out_exit_policy;
		}

		/* Recover policy->cpus using related_cpus */
		cpumask_copy(policy->cpus, policy->related_cpus);
	} else {
		cpumask_copy(policy->cpus, cpumask_of(cpu));

		/*
		 * Call driver. From then on the cpufreq must be able
		 * to accept all calls to ->verify and ->setpolicy for this CPU.
		 */
		ret = cpufreq_driver->init(policy);
		if (ret) {
			pr_debug("%s: %d: initialization failed\n", __func__,
				 __LINE__);
			goto out_free_policy;
		}

		/*
		 * The initialization has succeeded and the policy is online.
		 * If there is a problem with its frequency table, take it
		 * offline and drop it.
		 */
		ret = cpufreq_table_validate_and_sort(policy);
		if (ret)
			goto out_offline_policy;

		/* related_cpus should at least include policy->cpus. */
		cpumask_copy(policy->related_cpus, policy->cpus);
	}

	down_write(&policy->rwsem);
	/*
	 * affected cpus must always be the one, which are online. We aren't
	 * managing offline cpus here.
	 */
	cpumask_and(policy->cpus, policy->cpus, cpu_online_mask);

	if (new_policy) {
		for_each_cpu(j, policy->related_cpus) {
			per_cpu(cpufreq_cpu_data, j) = policy;
			add_cpu_dev_symlink(policy, j);
		}

		policy->min_freq_req = kzalloc(2 * sizeof(*policy->min_freq_req),
					       GFP_KERNEL);
		if (!policy->min_freq_req) {
			ret = -ENOMEM;
			goto out_destroy_policy;
		}

		ret = freq_qos_add_request(&policy->constraints,
					   policy->min_freq_req, FREQ_QOS_MIN,
					   policy->min);
		if (ret < 0) {
			/*
			 * So we don't call freq_qos_remove_request() for an
			 * uninitialized request.
			 */
			kfree(policy->min_freq_req);
			policy->min_freq_req = NULL;
			goto out_destroy_policy;
		}

		/*
		 * This must be initialized right here to avoid calling
		 * freq_qos_remove_request() on uninitialized request in case
		 * of errors.
		 */
		policy->max_freq_req = policy->min_freq_req + 1;

		ret = freq_qos_add_request(&policy->constraints,
					   policy->max_freq_req, FREQ_QOS_MAX,
					   policy->max);
		if (ret < 0) {
			policy->max_freq_req = NULL;
			goto out_destroy_policy;
		}

		blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
				CPUFREQ_CREATE_POLICY, policy);
	}

	if (cpufreq_driver->get && has_target()) {
		policy->cur = cpufreq_driver->get(policy->cpu);
		if (!policy->cur) {
			ret = -EIO;
			pr_err("%s: ->get() failed\n", __func__);
			goto out_destroy_policy;
		}
	}

	/*
	 * Sometimes boot loaders set CPU frequency to a value outside of
	 * frequency table present with cpufreq core. In such cases CPU might be
	 * unstable if it has to run on that frequency for long duration of time
	 * and so its better to set it to a frequency which is specified in
	 * freq-table. This also makes cpufreq stats inconsistent as
	 * cpufreq-stats would fail to register because current frequency of CPU
	 * isn't found in freq-table.
	 *
	 * Because we don't want this change to effect boot process badly, we go
	 * for the next freq which is >= policy->cur ('cur' must be set by now,
	 * otherwise we will end up setting freq to lowest of the table as 'cur'
	 * is initialized to zero).
	 *
	 * We are passing target-freq as "policy->cur - 1" otherwise
	 * __cpufreq_driver_target() would simply fail, as policy->cur will be
	 * equal to target-freq.
	 */
	if ((cpufreq_driver->flags & CPUFREQ_NEED_INITIAL_FREQ_CHECK)
	    && has_target()) {
		unsigned int old_freq = policy->cur;

		/* Are we running at unknown frequency ? */
		ret = cpufreq_frequency_table_get_index(policy, old_freq);
		if (ret == -EINVAL) {
			ret = __cpufreq_driver_target(policy, old_freq - 1,
						      CPUFREQ_RELATION_L);

			/*
			 * Reaching here after boot in a few seconds may not
			 * mean that system will remain stable at "unknown"
			 * frequency for longer duration. Hence, a BUG_ON().
			 */
			BUG_ON(ret);
			pr_info("%s: CPU%d: Running at unlisted initial frequency: %u KHz, changing to: %u KHz\n",
				__func__, policy->cpu, old_freq, policy->cur);
		}
	}

	if (new_policy) {
		ret = cpufreq_add_dev_interface(policy);
		if (ret)
			goto out_destroy_policy;

		cpufreq_stats_create_table(policy);

		write_lock_irqsave(&cpufreq_driver_lock, flags);
		list_add(&policy->policy_list, &cpufreq_policy_list);
		write_unlock_irqrestore(&cpufreq_driver_lock, flags);

		/*
		 * Register with the energy model before
		 * sched_cpufreq_governor_change() is called, which will result
		 * in rebuilding of the sched domains, which should only be done
		 * once the energy model is properly initialized for the policy
		 * first.
		 *
		 * Also, this should be called before the policy is registered
		 * with cooling framework.
		 */
		if (cpufreq_driver->register_em)
			cpufreq_driver->register_em(policy);
	}

	ret = cpufreq_init_policy(policy);
	if (ret) {
		pr_err("%s: Failed to initialize policy for cpu: %d (%d)\n",
		       __func__, cpu, ret);
		goto out_destroy_policy;
	}

	up_write(&policy->rwsem);

	kobject_uevent(&policy->kobj, KOBJ_ADD);

	if (cpufreq_thermal_control_enabled(cpufreq_driver))
		policy->cdev = of_cpufreq_cooling_register(policy);

	pr_debug("initialization complete\n");

	return 0;

out_destroy_policy:
	for_each_cpu(j, policy->real_cpus)
		remove_cpu_dev_symlink(policy, get_cpu_device(j));

	up_write(&policy->rwsem);

out_offline_policy:
	if (cpufreq_driver->offline)
		cpufreq_driver->offline(policy);

out_exit_policy:
	if (cpufreq_driver->exit)
		cpufreq_driver->exit(policy);

out_free_policy:
	cpufreq_policy_free(policy);
	return ret;
}