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, 246 insertions, 0 deletions

diff --git a/drivers/mfd/tps65090.c b/drivers/mfd/tps65090.c
new file mode 100644
index 000000000..24f42175a
--- /dev/null
+++ b/drivers/mfd/tps65090.c
@@ -0,0 +1,246 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Core driver for TI TPS65090 PMIC family
+ *
+ * Copyright (c) 2012, NVIDIA CORPORATION.  All rights reserved.
+ *
+ * Author: Venu Byravarasu <vbyravarasu@nvidia.com>
+ */
+
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/tps65090.h>
+#include <linux/of.h>
+#include <linux/err.h>
+
+#define NUM_INT_REG 2
+
+#define TPS65090_INT1_MASK_VAC_STATUS_CHANGE		1
+#define TPS65090_INT1_MASK_VSYS_STATUS_CHANGE		2
+#define TPS65090_INT1_MASK_BAT_STATUS_CHANGE		3
+#define TPS65090_INT1_MASK_CHARGING_STATUS_CHANGE	4
+#define TPS65090_INT1_MASK_CHARGING_COMPLETE		5
+#define TPS65090_INT1_MASK_OVERLOAD_DCDC1		6
+#define TPS65090_INT1_MASK_OVERLOAD_DCDC2		7
+#define TPS65090_INT2_MASK_OVERLOAD_DCDC3		0
+#define TPS65090_INT2_MASK_OVERLOAD_FET1		1
+#define TPS65090_INT2_MASK_OVERLOAD_FET2		2
+#define TPS65090_INT2_MASK_OVERLOAD_FET3		3
+#define TPS65090_INT2_MASK_OVERLOAD_FET4		4
+#define TPS65090_INT2_MASK_OVERLOAD_FET5		5
+#define TPS65090_INT2_MASK_OVERLOAD_FET6		6
+#define TPS65090_INT2_MASK_OVERLOAD_FET7		7
+
+static const struct resource charger_resources[] = {
+	{
+		.start  = TPS65090_IRQ_VAC_STATUS_CHANGE,
+		.end    = TPS65090_IRQ_VAC_STATUS_CHANGE,
+		.flags  = IORESOURCE_IRQ,
+	}
+};
+
+enum tps65090_cells {
+	PMIC = 0,
+	CHARGER = 1,
+};
+
+static struct mfd_cell tps65090s[] = {
+	[PMIC] = {
+		.name = "tps65090-pmic",
+	},
+	[CHARGER] = {
+		.name = "tps65090-charger",
+		.num_resources = ARRAY_SIZE(charger_resources),
+		.resources = &charger_resources[0],
+		.of_compatible = "ti,tps65090-charger",
+	},
+};
+
+static const struct regmap_irq tps65090_irqs[] = {
+	/* INT1 IRQs*/
+	[TPS65090_IRQ_VAC_STATUS_CHANGE] = {
+		.mask = TPS65090_INT1_MASK_VAC_STATUS_CHANGE,
+	},
+	[TPS65090_IRQ_VSYS_STATUS_CHANGE] = {
+		.mask = TPS65090_INT1_MASK_VSYS_STATUS_CHANGE,
+	},
+	[TPS65090_IRQ_BAT_STATUS_CHANGE] = {
+		.mask = TPS65090_INT1_MASK_BAT_STATUS_CHANGE,
+	},
+	[TPS65090_IRQ_CHARGING_STATUS_CHANGE] = {
+		.mask = TPS65090_INT1_MASK_CHARGING_STATUS_CHANGE,
+	},
+	[TPS65090_IRQ_CHARGING_COMPLETE] = {
+		.mask = TPS65090_INT1_MASK_CHARGING_COMPLETE,
+	},
+	[TPS65090_IRQ_OVERLOAD_DCDC1] = {
+		.mask = TPS65090_INT1_MASK_OVERLOAD_DCDC1,
+	},
+	[TPS65090_IRQ_OVERLOAD_DCDC2] = {
+		.mask = TPS65090_INT1_MASK_OVERLOAD_DCDC2,
+	},
+	/* INT2 IRQs*/
+	[TPS65090_IRQ_OVERLOAD_DCDC3] = {
+		.reg_offset = 1,
+		.mask = TPS65090_INT2_MASK_OVERLOAD_DCDC3,
+	},
+	[TPS65090_IRQ_OVERLOAD_FET1] = {
+		.reg_offset = 1,
+		.mask = TPS65090_INT2_MASK_OVERLOAD_FET1,
+	},
+	[TPS65090_IRQ_OVERLOAD_FET2] = {
+		.reg_offset = 1,
+		.mask = TPS65090_INT2_MASK_OVERLOAD_FET2,
+	},
+	[TPS65090_IRQ_OVERLOAD_FET3] = {
+		.reg_offset = 1,
+		.mask = TPS65090_INT2_MASK_OVERLOAD_FET3,
+	},
+	[TPS65090_IRQ_OVERLOAD_FET4] = {
+		.reg_offset = 1,
+		.mask = TPS65090_INT2_MASK_OVERLOAD_FET4,
+	},
+	[TPS65090_IRQ_OVERLOAD_FET5] = {
+		.reg_offset = 1,
+		.mask = TPS65090_INT2_MASK_OVERLOAD_FET5,
+	},
+	[TPS65090_IRQ_OVERLOAD_FET6] = {
+		.reg_offset = 1,
+		.mask = TPS65090_INT2_MASK_OVERLOAD_FET6,
+	},
+	[TPS65090_IRQ_OVERLOAD_FET7] = {
+		.reg_offset = 1,
+		.mask = TPS65090_INT2_MASK_OVERLOAD_FET7,
+	},
+};
+
+static const struct regmap_irq_chip tps65090_irq_chip = {
+	.name = "tps65090",
+	.irqs = tps65090_irqs,
+	.num_irqs = ARRAY_SIZE(tps65090_irqs),
+	.num_regs = NUM_INT_REG,
+	.status_base = TPS65090_REG_INTR_STS,
+	.unmask_base = TPS65090_REG_INTR_MASK,
+};
+
+static bool is_volatile_reg(struct device *dev, unsigned int reg)
+{
+	/* Nearly all registers have status bits mixed in, except a few */
+	switch (reg) {
+	case TPS65090_REG_INTR_MASK:
+	case TPS65090_REG_INTR_MASK2:
+	case TPS65090_REG_CG_CTRL0:
+	case TPS65090_REG_CG_CTRL1:
+	case TPS65090_REG_CG_CTRL2:
+	case TPS65090_REG_CG_CTRL3:
+	case TPS65090_REG_CG_CTRL4:
+	case TPS65090_REG_CG_CTRL5:
+		return false;
+	}
+	return true;
+}
+
+static const struct regmap_config tps65090_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = TPS65090_MAX_REG,
+	.num_reg_defaults_raw = TPS65090_NUM_REGS,
+	.cache_type = REGCACHE_MAPLE,
+	.volatile_reg = is_volatile_reg,
+};
+
+#ifdef CONFIG_OF
+static const struct of_device_id tps65090_of_match[] = {
+	{ .compatible = "ti,tps65090",},
+	{},
+};
+#endif
+
+static int tps65090_i2c_probe(struct i2c_client *client)
+{
+	struct tps65090_platform_data *pdata = dev_get_platdata(&client->dev);
+	int irq_base = 0;
+	struct tps65090 *tps65090;
+	int ret;
+
+	if (!pdata && !client->dev.of_node) {
+		dev_err(&client->dev,
+			"tps65090 requires platform data or of_node\n");
+		return -EINVAL;
+	}
+
+	if (pdata)
+		irq_base = pdata->irq_base;
+
+	tps65090 = devm_kzalloc(&client->dev, sizeof(*tps65090), GFP_KERNEL);
+	if (!tps65090)
+		return -ENOMEM;
+
+	tps65090->dev = &client->dev;
+	i2c_set_clientdata(client, tps65090);
+
+	tps65090->rmap = devm_regmap_init_i2c(client, &tps65090_regmap_config);
+	if (IS_ERR(tps65090->rmap)) {
+		ret = PTR_ERR(tps65090->rmap);
+		dev_err(&client->dev, "regmap_init failed with err: %d\n", ret);
+		return ret;
+	}
+
+	if (client->irq) {
+		ret = regmap_add_irq_chip(tps65090->rmap, client->irq,
+					  IRQF_ONESHOT | IRQF_TRIGGER_LOW, irq_base,
+					  &tps65090_irq_chip, &tps65090->irq_data);
+		if (ret) {
+			dev_err(&client->dev,
+				"IRQ init failed with err: %d\n", ret);
+			return ret;
+		}
+	} else {
+		/* Don't tell children they have an IRQ that'll never fire */
+		tps65090s[CHARGER].num_resources = 0;
+	}
+
+	ret = mfd_add_devices(tps65090->dev, -1, tps65090s,
+			      ARRAY_SIZE(tps65090s), NULL,
+			      0, regmap_irq_get_domain(tps65090->irq_data));
+	if (ret) {
+		dev_err(&client->dev, "add mfd devices failed with err: %d\n",
+			ret);
+		goto err_irq_exit;
+	}
+
+	return 0;
+
+err_irq_exit:
+	if (client->irq)
+		regmap_del_irq_chip(client->irq, tps65090->irq_data);
+	return ret;
+}
+
+
+static const struct i2c_device_id tps65090_id_table[] = {
+	{ "tps65090" },
+	{ }
+};
+
+static struct i2c_driver tps65090_driver = {
+	.driver	= {
+		.name	= "tps65090",
+		.suppress_bind_attrs = true,
+		.of_match_table = of_match_ptr(tps65090_of_match),
+	},
+	.probe		= tps65090_i2c_probe,
+	.id_table	= tps65090_id_table,
+};
+
+static int __init tps65090_init(void)
+{
+	return i2c_add_driver(&tps65090_driver);
+}
+subsys_initcall(tps65090_init);