sched_ext: Maintain an online cid mask in the scheduler arenagrafted

Schedulers on the default cid mapping treat [0, nr_online_cids) as the
online set and restart on hotplug. Schedulers that install their own mapping
with scx_bpf_cid_override() have no way to learn which cids are online: the
count no longer identifies members and the CPU-form cpumask is unusable from
cid programs. This is an obvious hole in the cid API.

Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's
arena, allocated alongside the per-CPU scratch masks and populated after the
cid mapping is finalized and before ops.init(), for child schedulers too.
The pointer stays valid through ops.exit() with no reference to take. It is
the arena offset as a void pointer, the same form struct_ops arena arguments
arrive in. The verifier types the void return as a scalar for the program's
arena cast.

The mask follows the SCX hotplug notifications: seeded from cpu_active_mask
and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask
only inside a hotplug transition. Updates walk the scheduler list under the
lock that also serializes unlinking. Reads are live, not atomic snapshots.
Root initialization excludes hotplug.

v2: Reworded the getter kerneldoc (Andrea Righi).

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

1 files changed, 508 insertions, 0 deletions

diff --git a/drivers/devfreq/exynos-bus.c b/drivers/devfreq/exynos-bus.c
new file mode 100644
index 000000000..b9ea7ad2e
--- /dev/null
+++ b/drivers/devfreq/exynos-bus.c
@@ -0,0 +1,508 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Generic Exynos Bus frequency driver with DEVFREQ Framework
+ *
+ * Copyright (c) 2016 Samsung Electronics Co., Ltd.
+ * Author : Chanwoo Choi <cw00.choi@samsung.com>
+ *
+ * This driver support Exynos Bus frequency feature by using
+ * DEVFREQ framework and is based on drivers/devfreq/exynos/exynos4_bus.c.
+ */
+
+#include <linux/clk.h>
+#include <linux/devfreq.h>
+#include <linux/devfreq-event.h>
+#include <linux/device.h>
+#include <linux/export.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/pm_opp.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/consumer.h>
+
+#define DEFAULT_SATURATION_RATIO	40
+
+struct exynos_bus {
+	struct device *dev;
+	struct platform_device *icc_pdev;
+
+	struct devfreq *devfreq;
+	struct devfreq_event_dev **edev;
+	unsigned int edev_count;
+	struct mutex lock;
+
+	unsigned long curr_freq;
+
+	int opp_token;
+	struct clk *clk;
+	unsigned int ratio;
+};
+
+/*
+ * Control the devfreq-event device to get the current state of bus
+ */
+#define exynos_bus_ops_edev(ops)				\
+static int exynos_bus_##ops(struct exynos_bus *bus)		\
+{								\
+	int i, ret;						\
+								\
+	for (i = 0; i < bus->edev_count; i++) {			\
+		if (!bus->edev[i])				\
+			continue;				\
+		ret = devfreq_event_##ops(bus->edev[i]);	\
+		if (ret < 0)					\
+			return ret;				\
+	}							\
+								\
+	return 0;						\
+}
+exynos_bus_ops_edev(enable_edev);
+exynos_bus_ops_edev(disable_edev);
+exynos_bus_ops_edev(set_event);
+
+static int exynos_bus_get_event(struct exynos_bus *bus,
+				struct devfreq_event_data *edata)
+{
+	struct devfreq_event_data event_data;
+	unsigned long load_count = 0, total_count = 0;
+	int i, ret = 0;
+
+	for (i = 0; i < bus->edev_count; i++) {
+		if (!bus->edev[i])
+			continue;
+
+		ret = devfreq_event_get_event(bus->edev[i], &event_data);
+		if (ret < 0)
+			return ret;
+
+		if (i == 0 || event_data.load_count > load_count) {
+			load_count = event_data.load_count;
+			total_count = event_data.total_count;
+		}
+	}
+
+	edata->load_count = load_count;
+	edata->total_count = total_count;
+
+	return ret;
+}
+
+/*
+ * devfreq function for both simple-ondemand and passive governor
+ */
+static int exynos_bus_target(struct device *dev, unsigned long *freq, u32 flags)
+{
+	struct exynos_bus *bus = dev_get_drvdata(dev);
+	struct dev_pm_opp *new_opp;
+	int ret = 0;
+
+	/* Get correct frequency for bus. */
+	new_opp = devfreq_recommended_opp(dev, freq, flags);
+	if (IS_ERR(new_opp)) {
+		dev_err(dev, "failed to get recommended opp instance\n");
+		return PTR_ERR(new_opp);
+	}
+
+	dev_pm_opp_put(new_opp);
+
+	/* Change voltage and frequency according to new OPP level */
+	mutex_lock(&bus->lock);
+	ret = dev_pm_opp_set_rate(dev, *freq);
+	if (!ret)
+		bus->curr_freq = *freq;
+
+	mutex_unlock(&bus->lock);
+
+	return ret;
+}
+
+static int exynos_bus_get_dev_status(struct device *dev,
+				     struct devfreq_dev_status *stat)
+{
+	struct exynos_bus *bus = dev_get_drvdata(dev);
+	struct devfreq_event_data edata;
+	int ret;
+
+	stat->current_frequency = bus->curr_freq;
+
+	ret = exynos_bus_get_event(bus, &edata);
+	if (ret < 0) {
+		dev_err(dev, "failed to get event from devfreq-event devices\n");
+		stat->total_time = stat->busy_time = 0;
+		goto err;
+	}
+
+	stat->busy_time = (edata.load_count * 100) / bus->ratio;
+	stat->total_time = edata.total_count;
+
+	dev_dbg(dev, "Usage of devfreq-event : %lu/%lu\n", stat->busy_time,
+							stat->total_time);
+
+err:
+	ret = exynos_bus_set_event(bus);
+	if (ret < 0) {
+		dev_err(dev, "failed to set event to devfreq-event devices\n");
+		return ret;
+	}
+
+	return ret;
+}
+
+static void exynos_bus_exit(struct device *dev)
+{
+	struct exynos_bus *bus = dev_get_drvdata(dev);
+	int ret;
+
+	ret = exynos_bus_disable_edev(bus);
+	if (ret < 0)
+		dev_warn(dev, "failed to disable the devfreq-event devices\n");
+
+	platform_device_unregister(bus->icc_pdev);
+
+	dev_pm_opp_of_remove_table(dev);
+	dev_pm_opp_put_regulators(bus->opp_token);
+}
+
+static void exynos_bus_passive_exit(struct device *dev)
+{
+	struct exynos_bus *bus = dev_get_drvdata(dev);
+
+	platform_device_unregister(bus->icc_pdev);
+
+	dev_pm_opp_of_remove_table(dev);
+}
+
+static int exynos_bus_parent_parse_of(struct device_node *np,
+					struct exynos_bus *bus)
+{
+	struct device *dev = bus->dev;
+	const char *supplies[] = { "vdd", NULL };
+	int i, ret, count, size;
+
+	ret = dev_pm_opp_set_regulators(dev, supplies);
+	if (ret < 0) {
+		dev_err(dev, "failed to set regulators %d\n", ret);
+		return ret;
+	}
+
+	bus->opp_token = ret;
+
+	/*
+	 * Get the devfreq-event devices to get the current utilization of
+	 * buses. This raw data will be used in devfreq ondemand governor.
+	 */
+	count = devfreq_event_get_edev_count(dev, "devfreq-events");
+	if (count < 0) {
+		dev_err(dev, "failed to get the count of devfreq-event dev\n");
+		ret = count;
+		goto err_regulator;
+	}
+	bus->edev_count = count;
+
+	size = sizeof(*bus->edev) * count;
+	bus->edev = devm_kzalloc(dev, size, GFP_KERNEL);
+	if (!bus->edev) {
+		ret = -ENOMEM;
+		goto err_regulator;
+	}
+
+	for (i = 0; i < count; i++) {
+		bus->edev[i] = devfreq_event_get_edev_by_phandle(dev,
+							"devfreq-events", i);
+		if (IS_ERR(bus->edev[i])) {
+			ret = -EPROBE_DEFER;
+			goto err_regulator;
+		}
+	}
+
+	/*
+	 * Optionally, Get the saturation ratio according to Exynos SoC
+	 * When measuring the utilization of each AXI bus with devfreq-event
+	 * devices, the measured real cycle might be much lower than the
+	 * total cycle of bus during sampling rate. In result, the devfreq
+	 * simple-ondemand governor might not decide to change the current
+	 * frequency due to too utilization (= real cycle/total cycle).
+	 * So, this property is used to adjust the utilization when calculating
+	 * the busy_time in exynos_bus_get_dev_status().
+	 */
+	if (of_property_read_u32(np, "exynos,saturation-ratio", &bus->ratio))
+		bus->ratio = DEFAULT_SATURATION_RATIO;
+
+	return 0;
+
+err_regulator:
+	dev_pm_opp_put_regulators(bus->opp_token);
+
+	return ret;
+}
+
+static int exynos_bus_parse_of(struct exynos_bus *bus)
+{
+	struct device *dev = bus->dev;
+	struct dev_pm_opp *opp;
+	unsigned long rate;
+	int ret;
+
+	/* Get the clock to provide each bus with source clock */
+	bus->clk = devm_clk_get_enabled(dev, "bus");
+	if (IS_ERR(bus->clk))
+		return dev_err_probe(dev, PTR_ERR(bus->clk),
+				"failed to get bus clock\n");
+
+	/* Get the freq and voltage from OPP table to scale the bus freq */
+	ret = dev_pm_opp_of_add_table(dev);
+	if (ret < 0) {
+		dev_err(dev, "failed to get OPP table\n");
+		return ret;
+	}
+
+	rate = clk_get_rate(bus->clk);
+
+	opp = devfreq_recommended_opp(dev, &rate, 0);
+	if (IS_ERR(opp)) {
+		dev_err(dev, "failed to find dev_pm_opp\n");
+		ret = PTR_ERR(opp);
+		goto err_opp;
+	}
+	bus->curr_freq = dev_pm_opp_get_freq(opp);
+	dev_pm_opp_put(opp);
+
+	return 0;
+
+err_opp:
+	dev_pm_opp_of_remove_table(dev);
+
+	return ret;
+}
+
+static int exynos_bus_profile_init(struct exynos_bus *bus,
+				   struct devfreq_dev_profile *profile)
+{
+	struct device *dev = bus->dev;
+	struct devfreq_simple_ondemand_data *ondemand_data;
+	int ret;
+
+	/* Initialize the struct profile and governor data for parent device */
+	profile->polling_ms = 50;
+	profile->target = exynos_bus_target;
+	profile->get_dev_status = exynos_bus_get_dev_status;
+	profile->exit = exynos_bus_exit;
+
+	ondemand_data = devm_kzalloc(dev, sizeof(*ondemand_data), GFP_KERNEL);
+	if (!ondemand_data)
+		return -ENOMEM;
+
+	ondemand_data->upthreshold = 40;
+	ondemand_data->downdifferential = 5;
+
+	/* Add devfreq device to monitor and handle the exynos bus */
+	bus->devfreq = devm_devfreq_add_device(dev, profile,
+						DEVFREQ_GOV_SIMPLE_ONDEMAND,
+						ondemand_data);
+	if (IS_ERR(bus->devfreq)) {
+		dev_err(dev, "failed to add devfreq device\n");
+		return PTR_ERR(bus->devfreq);
+	}
+
+	/* Register opp_notifier to catch the change of OPP  */
+	ret = devm_devfreq_register_opp_notifier(dev, bus->devfreq);
+	if (ret < 0) {
+		dev_err(dev, "failed to register opp notifier\n");
+		return ret;
+	}
+
+	/*
+	 * Enable devfreq-event to get raw data which is used to determine
+	 * current bus load.
+	 */
+	ret = exynos_bus_enable_edev(bus);
+	if (ret < 0) {
+		dev_err(dev, "failed to enable devfreq-event devices\n");
+		return ret;
+	}
+
+	ret = exynos_bus_set_event(bus);
+	if (ret < 0) {
+		dev_err(dev, "failed to set event to devfreq-event devices\n");
+		goto err_edev;
+	}
+
+	return 0;
+
+err_edev:
+	if (exynos_bus_disable_edev(bus))
+		dev_warn(dev, "failed to disable the devfreq-event devices\n");
+
+	return ret;
+}
+
+static int exynos_bus_profile_init_passive(struct exynos_bus *bus,
+					   struct devfreq_dev_profile *profile)
+{
+	struct device *dev = bus->dev;
+	struct devfreq_passive_data *passive_data;
+	struct devfreq *parent_devfreq;
+
+	/* Initialize the struct profile and governor data for passive device */
+	profile->target = exynos_bus_target;
+	profile->exit = exynos_bus_passive_exit;
+
+	/* Get the instance of parent devfreq device */
+	parent_devfreq = devfreq_get_devfreq_by_phandle(dev, "devfreq", 0);
+	if (IS_ERR(parent_devfreq))
+		return -EPROBE_DEFER;
+
+	passive_data = devm_kzalloc(dev, sizeof(*passive_data), GFP_KERNEL);
+	if (!passive_data)
+		return -ENOMEM;
+
+	passive_data->parent = parent_devfreq;
+
+	/* Add devfreq device for exynos bus with passive governor */
+	bus->devfreq = devm_devfreq_add_device(dev, profile, DEVFREQ_GOV_PASSIVE,
+						passive_data);
+	if (IS_ERR(bus->devfreq)) {
+		dev_err(dev,
+			"failed to add devfreq dev with passive governor\n");
+		return PTR_ERR(bus->devfreq);
+	}
+
+	return 0;
+}
+
+static int exynos_bus_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node, *node;
+	struct devfreq_dev_profile *profile;
+	struct exynos_bus *bus;
+	int ret, max_state;
+	unsigned long min_freq, max_freq;
+	bool passive = false;
+
+	if (!np) {
+		dev_err(dev, "failed to find devicetree node\n");
+		return -EINVAL;
+	}
+
+	bus = devm_kzalloc(&pdev->dev, sizeof(*bus), GFP_KERNEL);
+	if (!bus)
+		return -ENOMEM;
+	mutex_init(&bus->lock);
+	bus->dev = &pdev->dev;
+	platform_set_drvdata(pdev, bus);
+
+	profile = devm_kzalloc(dev, sizeof(*profile), GFP_KERNEL);
+	if (!profile)
+		return -ENOMEM;
+
+	node = of_parse_phandle(dev->of_node, "devfreq", 0);
+	if (node) {
+		of_node_put(node);
+		passive = true;
+	} else {
+		ret = exynos_bus_parent_parse_of(np, bus);
+		if (ret < 0)
+			return ret;
+	}
+
+	/* Parse the device-tree to get the resource information */
+	ret = exynos_bus_parse_of(bus);
+	if (ret < 0)
+		goto err_reg;
+
+	if (passive)
+		ret = exynos_bus_profile_init_passive(bus, profile);
+	else
+		ret = exynos_bus_profile_init(bus, profile);
+
+	if (ret < 0)
+		goto err;
+
+	/* Create child platform device for the interconnect provider */
+	if (of_property_present(dev->of_node, "#interconnect-cells")) {
+		bus->icc_pdev = platform_device_register_data(
+						dev, "exynos-generic-icc",
+						PLATFORM_DEVID_AUTO, NULL, 0);
+
+		if (IS_ERR(bus->icc_pdev)) {
+			ret = PTR_ERR(bus->icc_pdev);
+			goto err;
+		}
+	}
+
+	max_state = bus->devfreq->max_state;
+	min_freq = (bus->devfreq->freq_table[0] / 1000);
+	max_freq = (bus->devfreq->freq_table[max_state - 1] / 1000);
+	pr_info("exynos-bus: new bus device registered: %s (%6ld KHz ~ %6ld KHz)\n",
+			dev_name(dev), min_freq, max_freq);
+
+	return 0;
+
+err:
+	dev_pm_opp_of_remove_table(dev);
+err_reg:
+	dev_pm_opp_put_regulators(bus->opp_token);
+
+	return ret;
+}
+
+static void exynos_bus_shutdown(struct platform_device *pdev)
+{
+	struct exynos_bus *bus = dev_get_drvdata(&pdev->dev);
+
+	devfreq_suspend_device(bus->devfreq);
+}
+
+static int exynos_bus_resume(struct device *dev)
+{
+	struct exynos_bus *bus = dev_get_drvdata(dev);
+	int ret;
+
+	ret = exynos_bus_enable_edev(bus);
+	if (ret < 0) {
+		dev_err(dev, "failed to enable the devfreq-event devices\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static int exynos_bus_suspend(struct device *dev)
+{
+	struct exynos_bus *bus = dev_get_drvdata(dev);
+	int ret;
+
+	ret = exynos_bus_disable_edev(bus);
+	if (ret < 0) {
+		dev_err(dev, "failed to disable the devfreq-event devices\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(exynos_bus_pm,
+				exynos_bus_suspend, exynos_bus_resume);
+
+static const struct of_device_id exynos_bus_of_match[] = {
+	{ .compatible = "samsung,exynos-bus", },
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, exynos_bus_of_match);
+
+static struct platform_driver exynos_bus_platdrv = {
+	.probe		= exynos_bus_probe,
+	.shutdown	= exynos_bus_shutdown,
+	.driver = {
+		.name	= "exynos-bus",
+		.pm	= pm_sleep_ptr(&exynos_bus_pm),
+		.of_match_table = exynos_bus_of_match,
+	},
+};
+module_platform_driver(exynos_bus_platdrv);
+
+MODULE_SOFTDEP("pre: exynos_ppmu");
+MODULE_DESCRIPTION("Generic Exynos Bus frequency driver");
+MODULE_AUTHOR("Chanwoo Choi <cw00.choi@samsung.com>");
+MODULE_LICENSE("GPL v2");