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, 222 insertions, 0 deletions

diff --git a/drivers/hwmon/tmp103.c b/drivers/hwmon/tmp103.c
new file mode 100644
index 000000000..f13d24767
--- /dev/null
+++ b/drivers/hwmon/tmp103.c
@@ -0,0 +1,222 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Texas Instruments TMP103 SMBus temperature sensor driver
+ * Copyright (C) 2014 Heiko Schocher <hs@denx.de>
+ *
+ * Based on:
+ * Texas Instruments TMP102 SMBus temperature sensor driver
+ *
+ * Copyright (C) 2010 Steven King <sfking@fdwdc.com>
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/hwmon.h>
+#include <linux/err.h>
+#include <linux/device.h>
+#include <linux/regmap.h>
+
+#define TMP103_TEMP_REG		0x00
+#define TMP103_CONF_REG		0x01
+#define TMP103_TLOW_REG		0x02
+#define TMP103_THIGH_REG	0x03
+
+#define TMP103_CONF_M0		0x01
+#define TMP103_CONF_M1		0x02
+#define TMP103_CONF_LC		0x04
+#define TMP103_CONF_FL		0x08
+#define TMP103_CONF_FH		0x10
+#define TMP103_CONF_CR0		0x20
+#define TMP103_CONF_CR1		0x40
+#define TMP103_CONF_ID		0x80
+#define TMP103_CONF_SD		(TMP103_CONF_M1)
+#define TMP103_CONF_SD_MASK	(TMP103_CONF_M0 | TMP103_CONF_M1)
+
+#define TMP103_CONFIG		(TMP103_CONF_CR1 | TMP103_CONF_M1)
+#define TMP103_CONFIG_MASK	(TMP103_CONF_CR0 | TMP103_CONF_CR1 | \
+				 TMP103_CONF_M0 | TMP103_CONF_M1)
+
+static inline int tmp103_reg_to_mc(s8 val)
+{
+	return val * 1000;
+}
+
+static inline u8 tmp103_mc_to_reg(int val)
+{
+	return DIV_ROUND_CLOSEST(val, 1000);
+}
+
+static int tmp103_read(struct device *dev, enum hwmon_sensor_types type,
+		       u32 attr, int channel, long *temp)
+{
+	struct regmap *regmap = dev_get_drvdata(dev);
+	unsigned int regval;
+	int err, reg;
+
+	switch (attr) {
+	case hwmon_temp_input:
+		reg = TMP103_TEMP_REG;
+		break;
+	case hwmon_temp_min:
+		reg = TMP103_TLOW_REG;
+		break;
+	case hwmon_temp_max:
+		reg = TMP103_THIGH_REG;
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	err = regmap_read(regmap, reg, &regval);
+	if (err < 0)
+		return err;
+
+	*temp = tmp103_reg_to_mc(regval);
+
+	return 0;
+}
+
+static int tmp103_write(struct device *dev, enum hwmon_sensor_types type,
+			u32 attr, int channel, long temp)
+{
+	struct regmap *regmap = dev_get_drvdata(dev);
+	int reg;
+
+	switch (attr) {
+	case hwmon_temp_min:
+		reg = TMP103_TLOW_REG;
+		break;
+	case hwmon_temp_max:
+		reg = TMP103_THIGH_REG;
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	temp = clamp_val(temp, -55000, 127000);
+	return regmap_write(regmap, reg, tmp103_mc_to_reg(temp));
+}
+
+static umode_t tmp103_is_visible(const void *data, enum hwmon_sensor_types type,
+				 u32 attr, int channel)
+{
+	if (type != hwmon_temp)
+		return 0;
+
+	switch (attr) {
+	case hwmon_temp_input:
+		return 0444;
+	case hwmon_temp_min:
+	case hwmon_temp_max:
+		return 0644;
+	default:
+		return 0;
+	}
+}
+
+static const struct hwmon_channel_info * const tmp103_info[] = {
+	HWMON_CHANNEL_INFO(chip,
+			   HWMON_C_REGISTER_TZ),
+	HWMON_CHANNEL_INFO(temp,
+			   HWMON_T_INPUT | HWMON_T_MAX | HWMON_T_MIN),
+	NULL
+};
+
+static const struct hwmon_ops tmp103_hwmon_ops = {
+	.is_visible = tmp103_is_visible,
+	.read = tmp103_read,
+	.write = tmp103_write,
+};
+
+static const struct hwmon_chip_info tmp103_chip_info = {
+	.ops = &tmp103_hwmon_ops,
+	.info = tmp103_info,
+};
+
+static bool tmp103_regmap_is_volatile(struct device *dev, unsigned int reg)
+{
+	return reg == TMP103_TEMP_REG;
+}
+
+static const struct regmap_config tmp103_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = TMP103_THIGH_REG,
+	.volatile_reg = tmp103_regmap_is_volatile,
+};
+
+static int tmp103_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct device *hwmon_dev;
+	struct regmap *regmap;
+	int ret;
+
+	regmap = devm_regmap_init_i2c(client, &tmp103_regmap_config);
+	if (IS_ERR(regmap)) {
+		dev_err(dev, "failed to allocate register map\n");
+		return PTR_ERR(regmap);
+	}
+
+	ret = regmap_update_bits(regmap, TMP103_CONF_REG, TMP103_CONFIG_MASK,
+				 TMP103_CONFIG);
+	if (ret < 0) {
+		dev_err(&client->dev, "error writing config register\n");
+		return ret;
+	}
+
+	i2c_set_clientdata(client, regmap);
+	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
+							 regmap,
+							 &tmp103_chip_info,
+							 NULL);
+	return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+static int tmp103_suspend(struct device *dev)
+{
+	struct regmap *regmap = dev_get_drvdata(dev);
+
+	return regmap_update_bits(regmap, TMP103_CONF_REG,
+				  TMP103_CONF_SD_MASK, 0);
+}
+
+static int tmp103_resume(struct device *dev)
+{
+	struct regmap *regmap = dev_get_drvdata(dev);
+
+	return regmap_update_bits(regmap, TMP103_CONF_REG,
+				  TMP103_CONF_SD_MASK, TMP103_CONF_SD);
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(tmp103_dev_pm_ops, tmp103_suspend, tmp103_resume);
+
+static const struct i2c_device_id tmp103_id[] = {
+	{ .name = "tmp103" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, tmp103_id);
+
+static const struct of_device_id __maybe_unused tmp103_of_match[] = {
+	{ .compatible = "ti,tmp103" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, tmp103_of_match);
+
+static struct i2c_driver tmp103_driver = {
+	.driver = {
+		.name	= "tmp103",
+		.of_match_table = of_match_ptr(tmp103_of_match),
+		.pm	= pm_sleep_ptr(&tmp103_dev_pm_ops),
+	},
+	.probe		= tmp103_probe,
+	.id_table	= tmp103_id,
+};
+
+module_i2c_driver(tmp103_driver);
+
+MODULE_AUTHOR("Heiko Schocher <hs@denx.de>");
+MODULE_DESCRIPTION("Texas Instruments TMP103 temperature sensor driver");
+MODULE_LICENSE("GPL");